User Guide

Red Hat Developer Toolset 8.0

Installing and Using Red Hat Developer Toolset

Jaromír Hradílek

Red Hat Customer Content Services

Matt Newsome

Red Hat Software Engineering

Robert Krátký

Red Hat Customer Content Services

Vladimír Slávik

Red Hat Customer Content Services

Abstract

Red Hat Developer Toolset is a Red Hat offering for developers on the Red Hat Enterprise Linux platform. The Red Hat Developer Toolset User Guide provides an overview of this product, explains how to invoke and use the Red Hat Developer Toolset versions of the tools, and links to resources with more in-depth information.

Part I. Introduction

Chapter 1. Red Hat Developer Toolset

1.1. About Red Hat Developer Toolset

Red Hat Developer Toolset is a Red Hat offering for developers on the Red Hat Enterprise Linux platform. It provides a complete set of development and performance analysis tools that can be installed and used on multiple versions of Red Hat Enterprise Linux. Executables built with the Red Hat Developer Toolset toolchain can then also be deployed and run on multiple versions of Red Hat Enterprise Linux. For detailed compatibility information, see Section 1.3, “Compatibility”.

Red Hat Developer Toolset does not replace the default system tools provided with Red Hat Enterprise Linux 6 or 7 when installed on those platforms. Instead, a parallel set of developer tools provides an alternative, newer version of those tools for optional use by developers. The default compiler and debugger, for example, remain those provided by the base Red Hat Enterprise Linux system.

What Is New in Red Hat Developer Toolset 8.0

Since Red Hat Developer Toolset 4.1, the Red Hat Developer Toolset content is also available in the ISO format together with the rest of Red Hat Software Collections content at https://access.redhat.com/downloads, specifically for Server and Workstation. Note that packages that require the Optional channel, which are discussed in Section 1.5.3, “Installing Optional Packages”, cannot be installed from the ISO image.

Table 1.1. Red Hat Developer Toolset Components

NameVersionDescription

GCC

8.2.1

A portable compiler suite with support for C, C++, and Fortran.

binutils

2.30

A collection of binary tools and other utilities to inspect and manipulate object files and binaries.

elfutils

0.174

A collection of binary tools and other utilities to inspect and manipulate ELF files.

dwz

0.12

A tool to optimize DWARF debugging information contained in ELF shared libraries and ELF executables for size.

GDB

8.2

A command line debugger for programs written in C, C++, and Fortran.

ltrace

0.7.91

A debugging tool to display calls to dynamic libraries that a program makes. It can also monitor system calls executed by programs.

strace

4.24

A debugging tool to monitor system calls that a program uses and signals it receives.

memstomp

0.1.5

A debugging tool to identify calls to library functions with overlapping memory regions that are not allowed by various standards.

SystemTap

3.3

A tracing and probing tool to monitor the activities of the entire system without the need to instrument, recompile, install, and reboot.

Valgrind

3.14.0 (pre-release)

An instrumentation framework and a number of tools to profile applications in order to detect memory errors, identify memory management problems, and report any use of improper arguments in system calls.

OProfile

1.3.0

A system-wide profiler that uses the performance monitoring hardware on the processor to retrieve information about the kernel and executables on the system.

Dyninst

9.3.2

A library for instrumenting and working with user-space executables during their execution.

make

4.2.1

A dependency-tracking build automation tool.

Red Hat Developer Toolset differs from "Technology Preview" compiler releases previously supplied in Red Hat Enterprise Linux in two important respects:

  1. Red Hat Developer Toolset can be used on multiple major and minor releases of Red Hat Enterprise Linux, as detailed in Section 1.3, “Compatibility”.
  2. Unlike Technology Preview compilers and other tools shipped in earlier Red Hat Enterprise Linux, Red Hat Developer Toolset is fully supported under Red Hat Enterprise Linux Subscription Level Agreements, is functionally complete, and is intended for production use.

Important bug fixes and security errata are issued to Red Hat Developer Toolset subscribers in a similar manner to Red Hat Enterprise Linux for two years from the release of each major version release. A new major version of Red Hat Developer Toolset is released annually, providing significant updates for existing components and adding major new components. A single minor release, issued six months after each new major version release, provides a smaller update of bug fixes, security errata, and new minor components.

Additionally, the Red Hat Enterprise Linux Application Compatibility Specification also applies to Red Hat Developer Toolset (subject to some constraints on the use of newer C++11 language features, detailed in Section 2.2.4, “C++ Compatibility”).

Important

Applications and libraries provided by Red Hat Developer Toolset do not replace the Red Hat Enterprise Linux system versions, nor are they used in preference to the system versions. Using a framework called Software Collections, an additional set of developer tools is installed into the /opt/ directory and is explicitly enabled by the user on demand using the scl utility.

1.2. Main Features

Red Hat Developer Toolset 8.0 brings the following changes:

  • The Red Hat Developer Toolset version of the GNU Compiler Collection (GCC) has been upgraded to version 8.2.1 with many new features and bug fixes.
  • The Red Hat Developer Toolset version of the GNU Debugger (GDB) has been upgraded to version 8.2 with many new features and bug fixes.

For a full list of changes and features introduced in this release, see Appendix A, Changes in Version 8.0.

1.3. Compatibility

Red Hat Developer Toolset 8.0 is available for Red Hat Enterprise Linux 6 and 7 for a number of architectures. Figure 1.1, “Red Hat Developer Toolset 8.0 Compatibility Matrix” illustrates the support for binaries built with Red Hat Developer Toolset on a certain version of Red Hat Enterprise Linux when those binaries are run on various other versions of this system.

For ABI compatibility information, see Section 2.2.4, “C++ Compatibility”.

Figure 1.1. Red Hat Developer Toolset 8.0 Compatibility Matrix

Red Hat Developer Toolset 8.0 Compatibility Matrix

Architecture support

Red Hat Developer Toolset is available on the following architectures:

  • The 64-bit Intel and AMD architectures
  • The 64-bit ARM architecture
  • The IBM POWER architecture
  • The little-endian variant of IBM POWER architecture
  • The IBM Z architecture

1.4. Getting Access to Red Hat Developer Toolset

Red Hat Developer Toolset is an offering that is distributed as a part of the following content sets:

Red Hat Software Collections
This content set is available to customers with Red Hat Enterprise Linux 6 and 7 subscriptions listed at https://access.redhat.com/solutions/472793.
Red Hat Developer Tools

This content set is available to customers with deployments of Red Hat Enterprise Linux 7.

Note

Please note the difference: Red Hat Developer Toolset is an offering distributed as a part of the Red Hat Developer Tools content set.

Enable Red Hat Developer Toolset by using the Red Hat Subscription Management. For information on how to register your system with this subscription management service, see the Red Hat Subscription Management collection of guides.

1.4.1. Using Red Hat Software Collections

Complete the following steps to attach a subscription that provides access to the repository for Red Hat Software Collections (which includes Red Hat Developer Toolset), and then enable that repository:

  1. Determine the pool ID of a subscription that provides Red Hat Software Collections (and thus also Red Hat Developer Toolset). To do so, display a list of all subscriptions that are available for your system:

    # subscription-manager list --available

    For each available subscription, this command displays its name, unique identifier, expiration date, and other details related to your subscription. The pool ID is listed on a line beginning with Pool ID.

    For a complete list of subscriptions that provide access to Red Hat Developer Toolset, see https://access.redhat.com/solutions/472793.

  2. Attach the appropriate subscription to your system:

    # subscription-manager attach --pool=pool_id

    Replace pool_id with the pool ID you determined in the previous step. To verify the list of subscriptions your system has currently attached, at any time:

    # subscription-manager list --consumed
  3. Determine the exact name of the Red Hat Software Collections repository. Retrieve repository metadata and to display a list of available Yum repositories:

    # subscription-manager repos --list

    The repository names depend on the specific version of Red Hat Enterprise Linux you are using and are in the following format:

    rhel-variant-rhscl-version-rpms
    rhel-variant-rhscl-version-debug-rpms
    rhel-variant-rhscl-version-source-rpms

    In addition, certain packages, such as devtoolset-8-gcc-plugin-devel, depend on packages that are only available in the Optional channel. The repository names with these packages use the following format:

    rhel-version-variant-optional-rpms
    rhel-version-variant-optional-debug-rpms
    rhel-version-variant-optional-source-rpms

    For both the regular repositories and optional repositories, replace variant with the Red Hat Enterprise Linux system variant (server or workstation), and version with the Red Hat Enterprise Linux system version (6-eus, 6, or 7).

  4. Enable the repositories from step no. 3:

    # subscription-manager repos --enable repository

    Replace repository with the name of the repository to enable.

Once the subscription is attached to the system, you can install Red Hat Developer Toolset as described in Section 1.5, “Installing Red Hat Developer Toolset”. For more information on how to register your system using Red Hat Subscription Management and associate it with subscriptions, see the Red Hat Subscription Management collection of guides.

1.4.2. Using Red Hat Developer Tools

  1. Enable the rhel-7-variant-devtools-rpms repository:

    # subscription-manager repos --enable rhel-7-variant-devtools-rpms

    Replace variant with the Red Hat Enterprise Linux system variant (server or workstation).

  2. Add the Red Hat Developer Tools key to your system:

    # cd /etc/pki/rpm-gpg
    # wget -O RPM-GPG-KEY-redhat-devel https://www.redhat.com/security/data/a5787476.txt
    # rpm --import RPM-GPG-KEY-redhat-devel

Once the subscription is attached to the system, you can install Red Hat Developer Toolset as described in Section 1.5, “Installing Red Hat Developer Toolset”. For more information on how to register your system using Red Hat Subscription Management and associate it with subscriptions, see the Red Hat Subscription Management collection of guides.

1.5. Installing Red Hat Developer Toolset

Red Hat Developer Toolset is distributed as a collection of RPM packages that can be installed, updated, uninstalled, and inspected by using the standard package management tools that are included in Red Hat Enterprise Linux. Note that a valid subscription that provides access to the Red Hat Software Collections content set is required in order to install Red Hat Developer Toolset on your system. For detailed instructions on how to associate your system with an appropriate subscription and get access to Red Hat Developer Toolset, see Section 1.4, “Getting Access to Red Hat Developer Toolset”.

Important

Before installing Red Hat Developer Toolset, install all available Red Hat Enterprise Linux updates.

1.5.1. Installing All Available Components

To install all components that are included in Red Hat Developer Toolset, install the devtoolset-8 package:

# yum install devtoolset-8

This installs all development, debugging, and performance monitoring tools, and other dependent packages to the system. Alternatively, you can choose to install only a selected package group as described in Section 1.5.2, “Installing Individual Package Groups”.

Note

Note that since Red Hat Developer Toolset 3.0, the scl-utils package is not a part of Red Hat Developer Toolset, which is a change from preceding versions where the scl utility was installed along with the Red Hat Developer Toolset software collection.

1.5.2. Installing Individual Package Groups

To make it easier to install only certain components, such as the integrated development environment or the software development toolchain, Red Hat Developer Toolset is distributed with a number of meta packages that allow you to install selected package groups as described in Table 1.2, “Red Hat Developer Toolset Meta Packages”.

Table 1.2. Red Hat Developer Toolset Meta Packages

Package NameDescriptionInstalled Components

devtoolset-8-perftools

Performance monitoring tools

SystemTap, Valgrind, OProfile, Dyninst

devtoolset-8-toolchain

Development and debugging tools

GCC, make, GDB, binutils, elfutils, dwz, memstomp, strace, ltrace

To install any of these meta packages:

# yum install package_name

Replace package_name with a space-separated list of meta packages you want to install. For example, to install only the development and debugging toolchain and packages that depend on it:

# yum install devtoolset-8-toolchain

Alternatively, you can choose to install all available components as described in Section 1.5.1, “Installing All Available Components”.

1.5.3. Installing Optional Packages

Red Hat Developer Toolset is distributed with a number of optional packages that are not installed by default. To list all Red Hat Developer Toolset packages that are available to you but not installed on your system:

$ yum list available devtoolset-8-\*

To install any of these optional packages:

# yum install package_name

Replace package_name with a space-separated list of packages that you want to install. For example, to install the devtoolset-8-gdb-gdbserver and devtoolset-8-gdb-doc packages:

# yum install devtoolset-8-gdb-gdbserver devtoolset-8-gdb-doc

1.5.4. Installing Debugging Information

To install debugging information for any of the Red Hat Developer Toolset packages, make sure that the yum-utils package is installed and run:

# debuginfo-install package_name

For example, to install debugging information for the devtoolset-8-dwz package:

# debuginfo-install devtoolset-8-dwz

Note that in order to use this command, you need to have access to the repository with these packages. If your system is registered with Red Hat Subscription Management, enable the rhel-variant-rhscl-version-debug-rpms repository as described in Section 1.4, “Getting Access to Red Hat Developer Toolset”. For more information on how to get access to debuginfo packages, see https://access.redhat.com/site/solutions/9907.

Note

The devtoolset-8-package_name-debuginfo packages can conflict with the corresponding packages from the base Red Hat Enterprise Linux system or from other versions of Red Hat Developer Toolset. This conflict also occurs in a multilib environment, where 64-bit debuginfo packages conflict with 32-bit debuginfo packages.

Manually uninstall the conflicting debuginfo packages prior to installing Red Hat Developer Toolset 8.0 and install only relevant debuginfo packages when necessary.

1.6. Updating Red Hat Developer Toolset

1.6.1. Updating to a Minor Version

When a new minor version of Red Hat Developer Toolset is available, update your Red Hat Enterprise Linux installation:

# yum update

This updates all packages on your Red Hat Enterprise Linux system, including the Red Hat Developer Toolset versions of development, debugging, and performance monitoring tools, and other dependent packages.

Important

Use of Red Hat Developer Toolset requires the removal of any earlier pre-release versions of it. Additionally, it is not possible to update to Red Hat Developer Toolset 8.0 from a pre-release version of Red Hat Developer Toolset, including beta releases. If you have previously installed any pre-release version of Red Hat Developer Toolset, uninstall it from your system as described in Section 1.7, “Uninstalling Red Hat Developer Toolset” and install the new version as documented in Section 1.5, “Installing Red Hat Developer Toolset”.

1.6.2. Updating to a Major Version

When a new major version of Red Hat Developer Toolset is available, you can install it in parallel with the previous version. For detailed instructions on how to install Red Hat Developer Toolset on your system, see Section 1.5, “Installing Red Hat Developer Toolset”.

1.7. Uninstalling Red Hat Developer Toolset

To uninstall Red Hat Developer Toolset packages from your system:

# yum remove devtoolset-8\* libasan libatomic libcilkrts libitm liblsan libtsan libubsan

This removes the GNU Compiler Collection, GNU Debugger, binutils, and other packages that are a part of Red Hat Developer Toolset from the system.

Note

Red Hat Developer Toolset 8.0 for Red Hat Enterprise Linux 7 no longer includes the libatomic and libitm libraries, which the above command attempts to remove, because they are not required for a proper function of Red Hat Developer Toolset components on that system. Nevertheless, the above command works as expected even on Red Hat Enterprise Linux 7.

Note that the uninstallation of the tools provided by Red Hat Developer Toolset does not affect the Red Hat Enterprise Linux system versions of these tools.

1.8. Using Red Hat Developer Toolset Container Images

Docker-formatted container images can be used to run Red Hat Developer Toolset components inside virtual software containers, thus isolating them from the host system and allowing for their rapid deployment. For detailed description of the Red Hat Developer Toolset docker-formatted container images and Red Hat Developer Toolset Dockerfiles, see Using Red Hat Software Collections Container Images.

Note

The docker package, which contains the Docker daemon, command-line tool, and other necessary components for building and using docker-formatted container images, is currently available only for the Server variant of the Red Hat Enterprise Linux 7 product. Docker-formatted container images cannot be run on Red Hat Enterprise Linux 6, and Red Hat Developer Toolset Dockerfiles are not distributed for Red Hat Enterprise Linux 6.

Follow the instructions outlined at Getting Docker in RHEL 7 to set up an environment for building and using docker-formatted container images.

1.9. Additional Resources

For more information about Red Hat Developer Toolset and Red Hat Enterprise Linux, see the resources listed below.

Online Documentation

See Also

  • Appendix A, Changes in Version 8.0 — A list of changes and improvements over the version of the Red Hat Developer Toolset tools in the previous version of Red Hat Developer Toolset.

Part II. Development Tools

Chapter 2. GNU Compiler Collection (GCC)

The GNU Compiler Collection, commonly abbreviated GCC, is a portable compiler suite with support for a wide selection of programming languages.

Red Hat Developer Toolset is distributed with GCC 8.2.1. This version is more recent than the version included in Red Hat Enterprise Linux and provides a number of bug fixes and enhancements.

2.1. GNU C Compiler

2.1.1. Installing the C Compiler

In Red Hat Developer Toolset, the GNU C compiler is provided by the devtoolset-8-gcc package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

2.1.2. Using the C Compiler

To compile a C program on the command line, run the gcc compiler as follows:

$ scl enable devtoolset-8 'gcc -o output_file source_file...'

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the compiler creates a file named a.out by default.

When you are working on a project that consists of several source files, it is common to compile an object file for each of the source files first and then link these object files together. This way, when you change a single source file, you can recompile only this file without having to compile the entire project. To compile an object file on the command line,:

$ scl enable devtoolset-8 'gcc -o object_file -c source_file'

This creates an object file named object_file. If the -o option is omitted, the compiler creates a file named after the source file with the .o file extension. To link object files together and create a binary file:

$ scl enable devtoolset-8 'gcc -o output_file object_file...'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset gcc as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of gcc you are using at any point:

$ which gcc

Red Hat Developer Toolset’s gcc executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset gcc:

$ gcc -v

Example 2.1. Compiling a C Program on the Command Line

Consider a source file named hello.c with the following contents:

#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("Hello, World!\n");
  return 0;
}

Compile this source code on the command line by using the gcc compiler from Red Hat Developer Toolset:

$ scl enable devtoolset-8 'gcc -o hello hello.c'

This creates a new binary file called hello in the current working directory.

2.1.3. Running a C Program

When gcc compiles a program, it creates an executable binary file. To run this program on the command line, change to the directory with the executable file and run it:

$ ./file_name

Example 2.2. Running a C Program on the Command Line

Assuming that you have successfully compiled the hello binary file as shown in Example 2.1, “Compiling a C Program on the Command Line”, you can run it by typing the following at a shell prompt:

$ ./hello
Hello, World!

2.2. GNU C++ Compiler

2.2.1. Installing the C++ Compiler

In Red Hat Developer Toolset, the GNU C++ compiler is provided by the devtoolset-8-gcc-c++ package and is automatically installed with the devtoolset-8-toolchain package as described in Section 1.5, “Installing Red Hat Developer Toolset”.

2.2.2. Using the C++ Compiler

To compile a C++ program on the command line, run the g++ compiler as follows:

$ scl enable devtoolset-8 'g++ -o output_file source_file...'

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the g++ compiler creates a file named a.out by default.

When you are working on a project that consists of several source files, it is common to compile an object file for each of the source files first and then link these object files together. This way, when you change a single source file, you can recompile only this file without having to compile the entire project. To compile an object file on the command line:

$ scl enable devtoolset-8 'g++ -o object_file -c source_file'

This creates an object file named object_file. If the -o option is omitted, the g++ compiler creates a file named after the source file with the .o file extension. To link object files together and create a binary file:

$ scl enable devtoolset-8 'g++ -o output_file object_file...'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset g++ as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of g++ you are using at any point:

$ which g++

Red Hat Developer Toolset’s g++ executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset g++:

$ g++ -v

Example 2.3. Compiling a C++ Program on the Command Line

Consider a source file named hello.cpp with the following contents:

#include <iostream>

using namespace std;

int main(int argc, char *argv[]) {
  cout << "Hello, World!" << endl;
  return 0;
}

Compile this source code on the command line by using the g++ compiler from Red Hat Developer Toolset:

$ scl enable devtoolset-8 'g++ -o hello hello.cpp'

This creates a new binary file called hello in the current working directory.

2.2.3. Running a C++ Program

When g++ compiles a program, it creates an executable binary file. To run this program on the command line, change to the directory with the executable file and run it:

$ ./file_name

Example 2.4. Running a C++ Program on the Command Line

Assuming that you have successfully compiled the hello binary file as shown in Example 2.3, “Compiling a C++ Program on the Command Line”, you can run it:

$ ./hello
Hello, World!

2.2.4. C++ Compatibility

All compilers from Red Hat Enterprise Linux versions 5, 6, and 7 and from Red Hat Developer Toolset versions 1, 2, 3, 4, and 6 in any -std mode are compatible with any other of those compilers in C++98 mode.

A compiler in C++11 or C++14 mode is only guaranteed to be compatible with another compiler in C++11 or C++14 mode if they are from the same release series (for example from Red Hat Developer Toolset 6.x).

Important
  • Compilers in Red Hat Developer Toolset 7.x and 8.x can build code using C++17 but this capability is experimental and not supported by Red Hat.
  • All compatibility information mentioned in this section is relevant only for Red Hat-supplied versions of the GCC C++ compiler.

2.2.4.1. C++ ABI

Any C++98-compliant binaries or libraries built by the Red Hat Developer Toolset toolchain explicitly with -std=c++98 or -std=gnu++98 can be freely mixed with binaries and shared libraries built by the Red Hat Enterprise Linux 5, 6 or 7 system GCC.

The default language standard setting for Red Hat Developer Toolset is C++14 with GNU extensions, equivalent to explicitly using option -std=gnu++14.

Using the C++14 language version is supported in Red Hat Developer Toolset when all C++ objects compiled with the respective flag have been built using Red Hat Developer Toolset 6 or later. Objects compiled by the system GCC in its default mode of C++98 are also compatible, but objects compiled with the system GCC in C++11 or C++14 mode are not compatible.

Using the C++17 language version is experimental and possible in Red Hat Developer Toolset only when all C++ objects compiled with the respective flag have been built using the same major version of GCC. Because later major versions of Red Hat Developer Toolset may use a later major release of GCC, forward compatibility of objects, binary files, and libraries built with the -std=c++17 and -std=gnu++17 options cannot be guaranteed.

Important

Use of C++11 and C++14 features in your application requires careful consideration of the above ABI compatibility information.

The mixing of objects, binaries and libraries, built by the Red Hat Enterprise Linux 6 or 7 system toolchain GCC using the -std=c++0x or -std=gnu++0x flags, with those built with the -std=c++11 or -std=gnu++11 or -std=c++14 or -std=gnu++14 flags using the GCC in Red Hat Developer Toolset is explicitly not supported.

Aside from the C++11 and C++14 ABI, discussed above, the Red Hat Enterprise Linux Application Compatibility Specification is unchanged for Red Hat Developer Toolset. When mixing objects built with Red Hat Developer Toolset with those built with the Red Hat Enterprise Linux 6 or 7 toolchain (particularly .o/.a files), the Red Hat Developer Toolset toolchain should be used for any linkage. This ensures any newer library features provided only by Red Hat Developer Toolset are resolved at link-time.

A new standard mangling for SIMD vector types has been added to avoid name clashes on systems with vectors of varying lengths. The compiler in Red Hat Developer Toolset uses the new mangling by default. It is possible to use the previous standard mangling by adding the -fabi-version=2 or -fabi-version=3 options to GCC C++ compiler calls. To display a warning about code that uses the old mangling, use the -Wabi option.

On Red Hat Enterprise Linux 7, the GCC C++ compiler still uses the old mangling by default, but emits aliases with the new mangling on targets that support strong aliases. It is possible to use the new standard mangling by adding the -fabi-version=4 option to compiler calls. To display a warning about code that uses the old mangling, use the -Wabi option.

On Red Hat Enterprise Linux 6, the GCC C++ compiler supports only the previous standard mangling.

2.3. GNU Fortran Compiler

2.3.1. Installing the Fortran Compiler

In Red Hat Developer Toolset, the GNU Fortran compiler is provided by the devtoolset-8-gcc-gfortran package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

2.3.2. Using the Fortran Compiler

To compile a Fortran program on the command line, run the gfortran compiler as follows:

$ scl enable devtoolset-8 'gfortran -o output_file source_file...'

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the compiler creates a file named a.out by default.

When you are working on a project that consists of several source files, it is common to compile an object file for each of the source files first and then link these object files together. This way, when you change a single source file, you can recompile only this file without having to compile the entire project. To compile an object file on the command line:

$ scl enable devtoolset-8 'gfortran -o object_file -c source_file'

This creates an object file named object_file. If the -o option is omitted, the compiler creates a file named after the source file with the .o file extension. To link object files together and create a binary file:

$ scl enable devtoolset-8 'gfortran -o output_file object_file...'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset gfortran as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of gfortran you are using at any point:

$ which gfortran

Red Hat Developer Toolset’s gfortran executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset gfortran:

$ gfortran -v

Example 2.5. Compiling a Fortran Program on the Command Line

Consider a source file named hello.f with the following contents:

program hello
  print *, "Hello, World!"
end program hello

Compile this source code on the command line by using the gfortran compiler from Red Hat Developer Toolset:

$ scl enable devtoolset-8 'gfortran -o hello hello.f'

This creates a new binary file called hello in the current working directory.

2.3.3. Running a Fortran Program

When gfortran compiles a program, it creates an executable binary file. To run this program on the command line, change to the directory with the executable file and run it:

$ ./file_name

Example 2.6. Running a Fortran Program on the Command Line

Assuming that you have successfully compiled the hello binary file as shown in Example 2.5, “Compiling a Fortran Program on the Command Line”, you can run it:

$ ./hello
 Hello, World!

2.4. Specifics of GCC in Red Hat Developer Toolset

Static linking of libraries

Certain more recent library features are statically linked into applications built with Red Hat Developer Toolset to support execution on multiple versions of Red Hat Enterprise Linux. This creates an additional minor security risk as standard Red Hat Enterprise Linux errata do not change this code. If the need arises for developers to rebuild their applications due to this risk, Red Hat will communicate this using a security erratum.

Important

Because of this additional security risk, developers are strongly advised not to statically link their entire application for the same reasons.

Specify libraries after object files when linking

In Red Hat Developer Toolset, libraries are linked using linker scripts which might specify some symbols through static archives. This is required to ensure compatibility with multiple versions of Red Hat Enterprise Linux. However, the linker scripts use the names of the respective shared object files. As a consequence, the linker uses different symbol handling rules than expected, and does not recognize symbols required by object files when the option adding the library is specified before options specifying the object files:

$ scl enable devtoolset-8 'gcc -lsomelib objfile.o'

Using a library from the Red Hat Developer Toolset in this manner results in the linker error message undefined reference to symbol. To prevent this problem, follow the standard linking practice, and specify the option adding the library after the options specifying the object files:

$ scl enable devtoolset-8 'gcc objfile.o -lsomelib'

Note that this recommendation also applies when using the base Red Hat Enterprise Linux version of GCC.

2.5. Additional Resources

For more information about the GNU Compiler Collections and its features, see the resources listed below.

Installed Documentation

  • gcc(1) — The manual page for the gcc compiler provides detailed information on its usage; with few exceptions, g++ accepts the same command line options as gcc. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man gcc'
  • gfortran(1) — The manual page for the gfortran compiler provides detailed information on its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man gfortran'
  • C++ Standard Library Documentation — Documentation on the C++ standard library can be optionally installed:

    # yum install devtoolset-8-libstdc++-docs

    Once installed, HTML documentation is available at /opt/rh/devtoolset-8/root/usr/share/doc/devtoolset-8-libstdC++-docs-8.2.1/html/index.html.

Online Documentation

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 4, binutils — Instructions on using binutils, a collection of binary tools to inspect and manipulate object files and binaries.
  • Chapter 5, elfutils — Instructions on using elfutils, a collection of binary tools to inspect and manipulate ELF files.
  • Chapter 6, dwz — Instructions on using the dwz tool to optimize DWARF debugging information contained in ELF shared libraries and ELF executables for size.
  • Chapter 7, GNU Debugger (GDB) — Instructions on debugging programs written in C, C++, and Fortran.

Chapter 3. GNU make

The GNU make utility, commonly abbreviated make, is a tool for controlling the generation of executables from source files. make automatically determines which parts of a complex program have changed and need to be recompiled. make uses configuration files called Makefiles to control the way programs are built.

Red Hat Developer Toolset is distributed with make 4.2.1. This version is more recent than the version included in Red Hat Enterprise Linux and provides a number of bug fixes and enhancements.

3.1. Installing make

In Red Hat Developer Toolset, GNU make is provided by the devtoolset-8-make package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

3.2. Using make

To build a program without using a Makefile, run the make tool as follows:

$ scl enable devtoolset-8 'make source_file_without_extension'

This command makes use of implicit rules that are defined for a number of programming languages, including C, C++, and Fortran. The result is a binary file named source_file_without_extension in the current working directory.

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset make as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of make you are using at any point:

$ which make

Red Hat Developer Toolset’s make executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset make:

$ make -v

Example 3.1. Building a C Program Using make

Consider a source file named hello.c with the following contents:

#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("Hello, World!\n");
  return 0;
}

Build this source code using the implicit rules defined by the make utility from Red Hat Developer Toolset:

$ scl enable devtoolset-8 'make hello'
cc     hello.c   -o hello

This creates a new binary file called hello in the current working directory.

3.3. Using Makefiles

To build complex programs that consist of a number of source files, make uses configuration files called Makefiles that control how to compile the components of a program and build the final executable. Makefiles can also contain instructions for cleaning the working directory, installing and uninstalling program files, and other operations.

make automatically uses files named GNUmakefile, makefile, or Makefile in the current directory. To specify another file name, use the -f option:

$ make -f make_file

Describing the details of Makefile syntax is beyond the scope of this guide. See GNU make, the upstream GNU make manual, which provides an in-depth description of the GNU make utility, Makefile syntax, and their usage.

The full make manual is also available in the Texinfo format as a part of your installation. To view this manual:

$ scl enable devtoolset-8 'info make'

Example 3.2. Building a C Program Using a Makefile

Consider the following universal Makefile named Makefile for building the simple C program introduced in Example 3.1, “Building a C Program Using make”. The Makefile defines some variables and specifies four rules, which consist of targets and their recipes. Note that the lines with recipes must start with the TAB character:

CC=gcc
CFLAGS=-c -Wall
SOURCE=hello.c
OBJ=$(SOURCE:.c=.o)
EXE=hello

all: $(SOURCE) $(EXE)

$(EXE): $(OBJ)
        $(CC) $(OBJ) -o $@

.o: .c
        $(CC) $(CFLAGS) $< -o $@

clean:
        rm -rf $(OBJ) $(EXE)

To build the hello.c program using this Makefile, run the make utility:

$ scl enable devtoolset-8 'make'
gcc -c -Wall hello.c -o hello.o
gcc hello.o -o hello

This creates a new object file hello.o and a new binary file called hello in the current working directory.

To clean the working directory, run:

$ scl enable devtoolset-8 'make clean'
rm -rf hello.o hello

This removes the object and binary files from the working directory.

3.4. Additional Resources

For more information about the GNU make tool and its features, see the resources listed below.

Installed Documentation

  • make(1) — The manual page for the make utility provides information on its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man make'
  • The full make manual, which includes detailed information about Makefile syntax, is also available in the Texinfo format. To display the info manual for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'info make'

Online Documentation

  • GNU make — The upstream GNU make manual provides an in-depth description of the GNU make utility, Makefile syntax, and their usage.

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 2, GNU Compiler Collection (GCC) — Instructions on using the GNU Compiler Collection, a portable compiler suite with support for a wide selection of programming languages.
  • Chapter 4, binutils — Instructions on using binutils, a collection of binary tools to inspect and manipulate object files and binaries.
  • Chapter 5, elfutils — Instructions on using elfutils, a collection of binary tools to inspect and manipulate ELF files.
  • Chapter 6, dwz — Instructions on using the dwz tool to optimize DWARF debugging information contained in ELF shared libraries and ELF executables for size.
  • Chapter 7, GNU Debugger (GDB) — Instructions on debugging programs written in C, C++, and Fortran.

Chapter 4. binutils

binutils is a collection of various binary tools, such as the GNU linker, GNU assembler, and other utilities that allow you to inspect and manipulate object files and binaries. See Table 4.1, “Tools Included in binutils for Red Hat Developer Toolset” for a complete list of binary tools that are distributed with the Red Hat Developer Toolset version of binutils.

Red Hat Developer Toolset is distributed with binutils 2.30. This version is more recent than the version included in Red Hat Enterprise Linux and the previous release of Red Hat Developer Toolset and provides bug fixes and enhancements.

Table 4.1. Tools Included in binutils for Red Hat Developer Toolset

NameDescription

addr2line

Translates addresses into file names and line numbers.

ar

Creates, modifies, and extracts files from archives.

as

The GNU assembler.

c++filt

Decodes mangled C++ symbols.

dwp

Combines DWARF object files into a single DWARF package file.

elfedit

Examines and edits ELF files.

gprof

Display profiling information.

ld

The GNU linker.

ld.bfd

An alternative to the GNU linker.

ld.gold

Another alternative to the GNU linker.

nm

Lists symbols from object files.

objcopy

Copies and translates object files.

objdump

Displays information from object files.

ranlib

Generates an index to the contents of an archive to make access to this archive faster.

readelf

Displays information about ELF files.

size

Lists section sizes of object or archive files.

strings

Displays printable character sequences in files.

strip

Discards all symbols from object files.

4.1. Installing binutils

In Red Hat Developer Toolset, binutils are provided by the devtoolset-8-binutils package and are automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

4.2. Using the GNU Assembler

To produce an object file from an assembly language program, run the as tool as follows:

$ scl enable devtoolset-8 'as option ... -o object_file source_file'

This creates an object file named object_file in the current working directory.

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset as as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of as you are using at any point:

$ which as

Red Hat Developer Toolset’s as executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset as:

$ as -v

4.3. Using the GNU Linker

To create an executable binary file or a library from object files, run the ld tool as follows:

$ scl enable devtoolset-8 'ld option ... -o output_file object_file ...'

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the compiler creates a file named a.out by default.

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset ld as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of ld you are using at any point:

$ which ld

Red Hat Developer Toolset’s ld executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset ld:

$ ld -v

4.4. Using Other Binary Tools

The binutils provide many binary tools other than a linker and an assembler. For a complete list of these tools, see Table 4.1, “Tools Included in binutils for Red Hat Developer Toolset”.

To execute any of the tools that are a part of binutils:

$ scl enable devtoolset-8 'tool option ... file_name'

See Table 4.1, “Tools Included in binutils for Red Hat Developer Toolset” for a list of tools that are distributed with binutils. For example, to use the objdump tool to inspect an object file:

$ scl enable devtoolset-8 'objdump option ... object_file'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset binary tools as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of binutils you are using at any point:

$ which objdump

Red Hat Developer Toolset’s objdump executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset objdump:

$ objdump -v

4.5. Specifics of binutils in Red Hat Developer Toolset

Static linking of libraries

Certain more recent library features are statically linked into applications built with Red Hat Developer Toolset to support execution on multiple versions of Red Hat Enterprise Linux. This creates an additional minor security risk as standard Red Hat Enterprise Linux errata do not change this code. If the need arises for developers to rebuild their applications due to this risk, Red Hat will communicate this using a security erratum.

Important

Because of this additional security risk, developers are strongly advised not to statically link their entire application for the same reasons.

Specify libraries after object files when linking

In Red Hat Developer Toolset, libraries are linked using linker scripts which might specify some symbols through static archives. This is required to ensure compatibility with multiple versions of Red Hat Enterprise Linux. However, the linker scripts use the names of the respective shared object files. As a consequence, the linker uses different symbol handling rules than expected, and does not recognize symbols required by object files when the option adding the library is specified before options specifying the object files:

$ scl enable devtoolset-8 'ld -lsomelib objfile.o'

Using a library from the Red Hat Developer Toolset in this manner results in the linker error message undefined reference to symbol. To prevent this problem, follow the standard linking practice, and specify the option adding the library after the options specifying the object files:

$ scl enable devtoolset-8 'ld objfile.o -lsomelib'

Note that this recommendation also applies when using the base Red Hat Enterprise Linux version of binutils.

4.6. Additional Resources

For more information about binutils, see the resources listed below.

Installed Documentation

  • as(1), ld(1), addr2line(1), ar(1), c++filt(1), dwp(1), elfedit(1), gprof(1), nm(1), objcopy(1), objdump(1), ranlib(1), readelf(1), size(1), strings(1), strip(1), — Manual pages for various binutils tools provide more information about their respective usage. To display a manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man tool'

Online Documentation

See Also

Chapter 5. elfutils

elfutils is a collection of various binary tools, such as eu-objdump, eu-readelf, and other utilities that allow you to inspect and manipulate ELF files. See Table 5.1, “Tools Included in elfutils for Red Hat Developer Toolset” for a complete list of binary tools that are distributed with the Red Hat Developer Toolset version of elfutils.

Red Hat Developer Toolset is distributed with elfutils 0.174. This version is more recent than the version included the previous release of Red Hat Developer Toolset and provides some bug fixes and enhancements.

Table 5.1. Tools Included in elfutils for Red Hat Developer Toolset

NameDescription

eu-addr2line

Translates addresses into file names and line numbers.

eu-ar

Creates, modifies, and extracts files from archives.

eu-elfcmp

Compares relevant parts of two ELF files for equality.

eu-elflint

Verifies that ELF files are compliant with the generic ABI (gABI) and processor-specific supplement ABI (psABI) specification.

eu-findtextrel

Locates the source of text relocations in files.

eu-make-debug-archive

Creates an offline archive for debugging.

eu-nm

Lists symbols from object files.

eu-objdump

Displays information from object files.

eu-ranlib

Generates an index to the contents of an archive to make access to this archive faster.

eu-readelf

Displays information about ELF files.

eu-size

Lists section sizes of object or archive files.

eu-stack

A new utility for unwinding processes and cores.

eu-strings

Displays printable character sequences in files.

eu-strip

Discards all symbols from object files.

eu-unstrip

Combines stripped files with separate symbols and debug information.

5.1. Installing elfutils

In Red Hat Developer Toolset, elfutils is provided by the devtoolset-8-elfutils package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

5.2. Using elfutils

To execute any of the tools that are part of elfutils, run the tool as follows:

$ scl enable devtoolset-8 'tool option ... file_name'

See Table 5.1, “Tools Included in elfutils for Red Hat Developer Toolset” for a list of tools that are distributed with elfutils. For example, to use the eu-objdump tool to inspect an object file:

$ scl enable devtoolset-8 'eu-objdump option ... object_file'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset binary tools as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of elfutils you are using at any point:

$ which eu-objdump

Red Hat Developer Toolset’s eu-objdump executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset eu-objdump:

$ eu-objdump -V

5.3. Additional Resources

For more information about elfutils, see the resources listed below.

See Also

Chapter 6. dwz

dwz is a command line tool that attempts to optimize DWARF debugging information contained in ELF shared libraries and ELF executables for size. To do so, dwz replaces DWARF information representation with equivalent smaller representation where possible and reduces the amount of duplication by using techniques from Appendix E of the DWARF Standard.

Red Hat Developer Toolset is distributed with dwz 0.12.

6.1. Installing dwz

In Red Hat Developer Toolset, the dwz utility is provided by the devtoolset-8-dwz package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

6.2. Using dwz

To optimize DWARF debugging information in a binary file, run the dwz tool as follows:

$ scl enable devtoolset-8 'dwz option... file_name'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset dwz as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of dwz you are using at any point:

$ which dwz

Red Hat Developer Toolset’s dwz executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset dwz:

$ dwz -v

6.3. Additional Resources

For more information about dwz and its features, see the resources listed below.

Installed Documentation

  • dwz(1) — The manual page for the dwz utility provides detailed information on its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man dwz'

See Also

Part III. Debugging Tools

Chapter 7. GNU Debugger (GDB)

The GNU Debugger, commonly abbreviated as GDB, is a command line tool that can be used to debug programs written in various programming languages. It allows you to inspect memory within the code being debugged, control the execution state of the code, detect the execution of particular sections of code, and much more.

Red Hat Developer Toolset is distributed with GDB 8.2. This version is more recent than the version included in Red Hat Enterprise Linux and the previous release of Red Hat Developer Toolset and provides some enhancements and numerous bug fixes.

7.1. Installing the GNU Debugger

In Red Hat Developer Toolset, the GNU Debugger is provided by the devtoolset-8-gdb package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

7.2. Preparing a Program for Debugging

Compiling Programs with Debugging Information

To compile a C program with debugging information that can be read by the GNU Debugger, make sure the gcc compiler is run with the -g option:

$ scl enable devtoolset-8 'gcc -g -o output_file input_file...'

Similarly, to compile a C++ program with debugging information:

$ scl enable devtoolset-8 'g++ -g -o output_file input_file...'

Example 7.1. Compiling a C Program With Debugging Information

Consider a source file named fibonacci.c that has the following contents:

#include <stdio.h>
#include <limits.h>

int main (int argc, char *argv[]) {
  unsigned long int a = 0;
  unsigned long int b = 1;
  unsigned long int sum;

  while (b < LONG_MAX) {
    printf("%ld ", b);
    sum = a + b;
    a = b;
    b = sum;
  }

  return 0;
}

Compile this program on the command line using GCC from Red Hat Developer Toolset with debugging information for the GNU Debugger:

$ scl enable devtoolset-8 'gcc -g -o fibonacci fibonacci.c'

This creates a new binary file called fibonacci in the current working directory.

Installing Debugging Information for Existing Packages

To install debugging information for a package that is already installed on the system:

# debuginfo-install package_name

Note that the yum-utils package must be installed for the debuginfo-install utility to be available on your system.

Example 7.2. Installing Debugging Information for the glibc Package

Install debugging information for the glibc package:

# debuginfo-install glibc
Loaded plugins: product-id, refresh-packagekit, subscription-manager
--> Running transaction check
---> Package glibc-debuginfo.x86_64 0:2.17-105.el7 will be installed
...

7.3. Running the GNU Debugger

To run the GNU Debugger on a program you want to debug:

$ scl enable devtoolset-8 'gdb file_name'

This starts the gdb debugger in interactive mode and displays the default prompt, (gdb). To quit the debugging session and return to the shell prompt, run the following command at any time:

(gdb) quit

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset gdb as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of gdb you are using at any point:

$ which gdb

Red Hat Developer Toolset’s gdb executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset gdb:

$ gdb -v

Example 7.3. Running the gdb Utility on the fibonacci Binary File

This example assumes that you have successfully compiled the fibonacci binary file as shown in Example 7.1, “Compiling a C Program With Debugging Information”.

Start debugging fibonacci with gdb:

$ scl enable devtoolset-8 'gdb fibonacci'
GNU gdb (GDB) Red Hat Enterprise Linux 8.2-2.el7
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from fibonacci...done.
(gdb)

7.4. Listing Source Code

To view the source code of the program you are debugging:

(gdb) list

Before you start the execution of the program you are debugging, gdb displays the first ten lines of the source code, and any subsequent use of this command lists another ten lines. Once you start the execution, gdb displays the lines that are surrounding the line on which the execution stops, typically when you set a breakpoint.

You can also display the code that is surrounding a particular line:

(gdb) list file_name:line_number

Similarly, to display the code that is surrounding the beginning of a particular function:

(gdb) list file_name:function_name

Note that you can change the number of lines the list command displays:

(gdb) set listsize number

Example 7.4. Listing the Source Code of the fibonacci Binary File

The fibonacci.c file listed in Example 7.1, “Compiling a C Program With Debugging Information” has exactly 17 lines. Assuming that you have compiled it with debugging information and you want the gdb utility to be capable of listing the entire source code, you can run the following command to change the number of listed lines to 20:

(gdb) set listsize 20

You can now display the entire source code of the file you are debugging by running the list command with no additional arguments:

(gdb) list
1       #include <stdio.h>
2       #include <limits.h>
3
4       int main (int argc, char *argv[]) {
5         unsigned long int a = 0;
6         unsigned long int b = 1;
7         unsigned long int sum;
8
9         while (b < LONG_MAX) {
10          printf("%ld ", b);
11          sum = a + b;
12          a = b;
13          b = sum;
14        }
15
16        return 0;
17      }

7.5. Setting Breakpoints

Setting a New Breakpoint

To set a new breakpoint at a certain line:

(gdb) break file_name:line_number

You can also set a breakpoint on a certain function:

(gdb) break file_name:function_name

Example 7.5. Setting a New Breakpoint

This example assumes that you have compiled the fibonacci.c file listed in Example 7.1, “Compiling a C Program With Debugging Information” with debugging information.

Set a new breakpoint at line 10:

(gdb) break 10
Breakpoint 1 at 0x4004e5: file fibonacci.c, line 10.

Listing Breakpoints

To display a list of currently set breakpoints:

(gdb) info breakpoints

Example 7.6. Listing Breakpoints

This example assumes that you have followed the instructions in Example 7.5, “Setting a New Breakpoint”.

Display the list of currently set breakpoints:

(gdb) info breakpoints
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000004004e5 in main at fibonacci.c:10

Deleting Existing Breakpoints

To delete a breakpoint that is set at a certain line:

(gdb) clear line_number

Similarly, to delete a breakpoint that is set on a certain function:

(gdb) clear function_name

Example 7.7. Deleting an Existing Breakpoint

This example assumes that you have compiled the fibonacci.c file listed in Example 7.1, “Compiling a C Program With Debugging Information” with debugging information.

Set a new breakpoint at line 7:

(gdb) break 7
Breakpoint 2 at 0x4004e3: file fibonacci.c, line 7.

Remove this breakpoint:

(gdb) clear 7
Deleted breakpoint 2

7.6. Starting Execution

To start an execution of the program you are debugging:

(gdb) run

If the program accepts any command line arguments, you can provide them as arguments to the run command:

(gdb) run argument

The execution stops when the first breakpoint (if any) is reached, when an error occurs, or when the program terminates.

Example 7.8. Executing the fibonacci Binary File

This example assumes that you have followed the instructions in Example 7.5, “Setting a New Breakpoint”.

Execute the fibonacci binary file:

(gdb) run
Starting program: /home/john/fibonacci

Breakpoint 1, main (argc=1, argv=0x7fffffffe4d8) at fibonacci.c:10
10          printf("%ld ", b);

7.7. Displaying Current Values

The gdb utility allows you to display the value of almost anything that is relevant to the program, from a variable of any complexity to a valid expression or even a library function. However, the most common task is to display the value of a variable.

To display the current value of a certain variable:

(gdb) print variable_name

Example 7.9. Displaying the Current Values of Variables

This example assumes that you have followed the instructions in Example 7.8, “Executing the fibonacci Binary File” and the execution of the fibonacci binary stopped after reaching the breakpoint at line 10.

Display the current values of variables a and b:

(gdb) print a
$1 = 0
(gdb) print b
$2 = 1

7.8. Continuing Execution

To resume the execution of the program you are debugging after it reached a breakpoint:

(gdb) continue

The execution stops again when another breakpoint is reached. To skip a certain number of breakpoints (typically when you are debugging a loop):

(gdb) continue number

The gdb utility also allows you to stop the execution after executing a single line of code:

(gdb) step

Finally, you can execute a certain number of lines:

(gdb) step number

Example 7.10. Continuing the Execution of the fibonacci Binary File

This example assumes that you have followed the instructions in Example 7.8, “Executing the fibonacci Binary File”, and the execution of the fibonacci binary stopped after reaching the breakpoint at line 10.

Resume the execution:

(gdb) continue
Continuing.

Breakpoint 1, main (argc=1, argv=0x7fffffffe4d8) at fibonacci.c:10
10          printf("%ld ", b);

The execution stops the next time the breakpoint is reached.

Execute the next three lines of code:

(gdb) step 3
13          b = sum;

This allows you to verify the current value of the sum variable before it is assigned to b:

(gdb) print sum
$3 = 2

7.9. Additional Resources

For more information about the GNU Debugger and all its features, see the resources listed below.

Installed Documentation

Installing the devtoolset-8-gdb-doc package provides the following documentation in HTML and PDF formats in the /opt/rh/devtoolset-7/root/usr/share/doc/devtoolset-8-gdb-doc-8.2 directory:

  • The Debugging with GDB book, which is a copy of the upstream material with the same name. The version of this document exactly corresponds to the version of GDB available in Red Hat Developer Toolset.
  • The GDB’s Obsolete Annotations document, which lists the obsolete GDB level 2 annotations.

Online Documentation

See Also

Chapter 8. strace

strace is a diagnostic and debugging tool for the command line that can be used to trace system calls that are made and received by a running process. It records the name of each system call, its arguments, and its return value, as well as signals received by the process and other interactions with the kernel, and prints this record to standard error output or a selected file.

Red Hat Developer Toolset is distributed with strace 4.24.

8.1. Installing strace

In Red Hat Enterprise Linux, the strace utility is provided by the devtoolset-8-strace package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

8.2. Using strace

To run the strace utility on a program you want to analyze:

$ scl enable devtoolset-8 'strace program argument...'

Replace program with the name of the program you want to analyze, and argument with any command line options and arguments you want to supply to this program. Alternatively, you can run the utility on an already running process by using the -p command line option followed by the process ID:

$ scl enable devtoolset-8 'strace -p process_id'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset strace as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of strace you are using at any point:

$ which strace

Red Hat Developer Toolset’s strace executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset strace:

$ strace -V

8.2.1. Redirecting Output to a File

By default, strace prints the name of each system call, its arguments and the return value to standard error output. To redirect this output to a file, use the -o command line option followed by the file name:

$ scl enable devtoolset-8 'strace -o file_name program argument...'

Replace file_name with the name of the file.

Example 8.1. Redirecting Output to a File

Consider a slightly modified version of the fibonacci file from Example 7.1, “Compiling a C Program With Debugging Information”. This executable file displays the Fibonacci sequence and optionally allows you to specify how many members of this sequence to list. Run the strace utility on this file and redirect the trace output to fibonacci.log:

$ scl enable devtoolset-8 'strace -o fibonacci.log ./fibonacci 20'
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765

This creates a new plain-text file called fibonacci.log in the current working directory.

8.2.2. Tracing Selected System Calls

To trace only a selected set of system calls, run the strace utility with the -e command line option:

$ scl enable devtoolset-8 'strace -e expression program argument...'

Replace expression with a comma-separated list of system calls to trace or any of the keywords listed in Table 8.1, “Commonly Used Values of the -e Option”. For a detailed description of all available values, see the strace(1) manual page.

Table 8.1. Commonly Used Values of the -e Option

ValueDescription

%file

System calls that accept a file name as an argument.

%process

System calls that are related to process management.

%network

System calls that are related to networking.

%signal

System calls that are related to signal management.

%ipc

System calls that are related to inter-process communication (IPC).

%desc

System calls that are related to file descriptors.

Note that the syntax -e expression is a shorthand for the full form -e trace=expression.

Example 8.2. Tracing Selected System Calls

Consider the employee file from Example 10.1, “Using memstomp”. Run the strace utility on this executable file and trace only the mmap and munmap system calls:

$ scl enable devtoolset-8 'strace -e mmap,munmap ./employee'
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f896c744000
mmap(NULL, 61239, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f896c735000
mmap(0x3146a00000, 3745960, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x3146a00000
mmap(0x3146d89000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x189000) = 0x3146d89000
mmap(0x3146d8e000, 18600, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x3146d8e000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f896c734000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f896c733000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f896c732000
munmap(0x7f896c735000, 61239)           = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f896c743000
John,john@example.comDoe,
+++ exited with 0 +++

8.2.3. Displaying Time Stamps

To prefix each line of the trace with the exact time of the day in hours, minutes, and seconds, run the strace utility with the -t command line option:

$ scl enable devtoolset-8 'strace -t program argument...'

To also display milliseconds, supply the -t option twice:

$ scl enable devtoolset-8 'strace -tt program argument...'

To prefix each line of the trace with the time required to execute the respective system call, use the -r command line option:

$ scl enable devtoolset-8 'strace -r program argument...'

Example 8.3. Displaying Time Stamps

Consider an executable file named pwd. Run the strace utility on this file and include time stamps in the output:

$ scl enable devtoolset-8 'strace -tt pwd'
19:43:28.011815 execve("./pwd", ["./pwd"], [/* 36 vars */]) = 0
19:43:28.012128 brk(0)                  = 0xcd3000
19:43:28.012174 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fc869cb0000
19:43:28.012427 open("/etc/ld.so.cache", O_RDONLY) = 3
19:43:28.012446 fstat(3, {st_mode=S_IFREG|0644, st_size=61239, ...}) = 0
19:43:28.012464 mmap(NULL, 61239, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fc869ca1000
19:43:28.012483 close(3)                = 0
...
19:43:28.013410 +++ exited with 0 +++

8.2.4. Displaying a Summary

To display a summary of how much time was required to execute each system call, how many times were these system calls executed, and how many errors were encountered during their execution, run the strace utility with the -c command line option:

$ scl enable devtoolset-8 'strace -c program argument...'

Example 8.4. Displaying a Summary

Consider an executable file named lsblk. Run the strace utility on this file and display a trace summary:

$ scl enable devtoolset-8 'strace -c lsblk > /dev/null'
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 80.88    0.000055           1       106        16 open
 19.12    0.000013           0       140           munmap
  0.00    0.000000           0       148           read
  0.00    0.000000           0         1           write
  0.00    0.000000           0       258           close
  0.00    0.000000           0        37         2 stat
...
------ ----------- ----------- --------- --------- ----------------
100.00    0.000068                  1790        35 total

8.2.5. Tampering with System Call Results

Simulating errors returned from system calls can help identify missing error handling in programs.

To make a program receive a generic error as the result of a particular system call, run the strace utility with the -e fault= option and supply the system call:

$ scl enable devtoolset-8 'strace -e fault=syscall program argument...'

To specify the error type or return value, use the -e inject= option:

$ scl enable devtoolset-8 'strace -e inject=syscall:error=error-type program argument'
$ scl enable devtoolset-8 'strace -e inject=syscall:retval=return-value program argument'

Note that specifying the error type and return value is mutually exclusive.

Example 8.5. Tampering with System Call Results

Consider an executable file named lsblk. Run the strace utility on this file and make the mmap() system call return an error:

$ scl enable devtoolset-8 'strace -e fault=mmap:error=EPERM lsblk > /dev/null'
execve("/usr/bin/lsblk", ["lsblk"], 0x7fff1c0e02a0 /* 54 vars */) = 0
brk(NULL)                               = 0x55d9e8b43000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 EPERM (Operation not permitted) (INJECTED)
writev(2, [{iov_base="lsblk", iov_len=5}, {iov_base=": ", iov_len=2}, {iov_base="error while loading shared libra"..., iov_len=36}, {iov_base=": ", iov_len=2}, {iov_base="", iov_len=0}, {iov_base="", iov_len=0}, {iov_base="cannot create cache for search p"..., iov_len=35}, {iov_base=": ", iov_len=2}, {iov_base="Cannot allocate memory", iov_len=22}, {iov_base="\n", iov_len=1}], 10lsblk: error while loading shared libraries: cannot create cache for search path: Cannot allocate memory
) = 105
exit_group(127)                         = ?
+++ exited with 127 +++

8.3. Additional Resources

For more information about strace and its features, see the resources listed below.

Installed Documentation

  • strace(1) — The manual page for the strace utility provides detailed information about its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man strace'

See Also

Chapter 9. ltrace

ltrace is a diagnostic and debugging tool for the command line that can be used to display calls that are made to shared libraries. It uses the dynamic library hooking mechanism, which prevents it from tracing calls to statically linked libraries. ltrace also displays return values of the library calls. The output is printed to standard error output or to a selected file.

Red Hat Developer Toolset is distributed with ltrace 0.7.91. While the base version ltrace remains the same as in the previous release of Red Hat Developer Toolset, various enhancements and bug fixes have ported.

9.1. Installing ltrace

In Red Hat Enterprise Linux, the ltrace utility is provided by the devtoolset-8-ltrace package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

9.2. Using ltrace

To run the ltrace utility on a program you want to analyze:

$ scl enable devtoolset-8 'ltrace program argument...'

Replace program with the name of the program you want to analyze, and argument with any command line options and arguments you want to supply to this program. Alternatively, you can run the utility on an already running process by using the -p command line option followed by the process ID:

$ scl enable devtoolset-8 'ltrace -p process_id'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset ltrace as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of ltrace you are using at any point:

$ which ltrace

Red Hat Developer Toolset’s ltrace executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset ltrace:

$ ltrace -V

9.2.1. Redirecting Output to a File

By default, ltrace prints the name of each system call, its arguments and the return value to standard error output. To redirect this output to a file, use the -o command line option followed by the file name:

$ scl enable devtoolset-8 'ltrace -o file_name program argument...'

Replace file_name with the name of the file.

Example 9.1. Redirecting Output to a File

Consider a slightly modified version of the fibonacci file from Example 7.1, “Compiling a C Program With Debugging Information”. This executable file displays the Fibonacci sequence and optionally allows you to specify how many members of this sequence to list. Run the ltrace utility on this file and redirect the trace output to fibonacci.log:

$ scl enable devtoolset-8 'ltrace -o fibonacci.log ./fibonacci 20'
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765

This creates a new plain-text file called fibonacci.log in the current working directory.

9.2.2. Tracing Selected Library Calls

To trace only a selected set of library calls, run the ltrace utility with the -e command line option:

$ scl enable devtoolset-8 'ltrace -e expression program argument...'

Replace expression with a chain of rules to specify the library calls to trace. The rules can consist of patterns that identify symbol names (such as malloc or free) and patterns that identify library SONAMEs (such as libc.so). For example, to trace call to the malloc and free function but to omit those that are done by the libc library:

$ scl enable devtoolset-8 'ltrace -e malloc+free-@libc.so* program'

Example 9.2. Tracing Selected Library Calls

Consider the ls command. Run the ltrace utility on this program and trace only the opendir, readdir, and closedir function calls:

$ scl enable devtoolset-8 'ltrace -e opendir+readdir+closedir ls'
ls->opendir(".")     = { 3 }
ls->readdir({ 3 })   = { 61533, "." }
ls->readdir({ 3 })   = { 131, ".." }
ls->readdir({ 3 })   = { 67185100, "BUILDROOT" }
ls->readdir({ 3 })   = { 202390772, "SOURCES" }
ls->readdir({ 3 })   = { 60249, "SPECS" }
ls->readdir({ 3 })   = { 67130110, "BUILD" }
ls->readdir({ 3 })   = { 136599168, "RPMS" }
ls->readdir({ 3 })   = { 202383274, "SRPMS" }
ls->readdir({ 3 })   = nil
ls->closedir({ 3 })  = 0
BUILD  BUILDROOT  RPMS  SOURCES  SPECS  SRPMS
+++ exited (status 0) +++

For a detailed description of available filter expressions, see the ltrace(1) manual page.

9.2.3. Displaying Time Stamps

To prefix each line of the trace with the exact time of the day in hours, minutes, and seconds, run the ltrace utility with the -t command line option:

$ scl enable devtoolset-8 'ltrace -t program argument...'

To also display milliseconds, supply the -t option twice:

$ scl enable devtoolset-8 'ltrace -tt program argument...'

To prefix each line of the trace with the time required to execute the respective system call, use the -r command line option:

$ scl enable devtoolset-8 'ltrace -r program argument...'

Example 9.3. Displaying Time Stamps

Consider the pwd command. Run the ltrace utility on this program and include time stamps in the output:

$ scl enable devtoolset-8 'ltrace -tt pwd'
13:27:19.631371 __libc_start_main([ "pwd" ] <unfinished ...>
13:27:19.632240 getenv("POSIXLY_CORRECT")                        = nil
13:27:19.632520 strrchr("pwd", '/')                              = nil
13:27:19.632786 setlocale(LC_ALL, "")                            = "en_US.UTF-8"
13:27:19.633220 bindtextdomain("coreutils", "/usr/share/locale") = "/usr/share/locale"
13:27:19.633471 textdomain("coreutils")                          = "coreutils"
(...)
13:27:19.637110  exited (status 0)

9.2.4. Displaying a Summary

To display a summary of how much time was required to execute each system call and how many times were these system calls executed, run the ltrace utility with the -c command line option:

$ scl enable devtoolset-8 'ltrace -c program argument...'

Example 9.4. Displaying a Summary

Consider the lsblk command. Run the ltrace utility on this program and display a trace summary:

$ scl enable devtoolset-8 'ltrace -c lsblk > /dev/null'
% time     seconds  usecs/call     calls      function
------ ----------- ----------- --------- --------------------
 53.60    0.261644      261644         1 __libc_start_main
  4.48    0.021848          58       374 mbrtowc
  4.41    0.021524          57       374 wcwidth
  4.39    0.021409          57       374 __ctype_get_mb_cur_max
  4.38    0.021359          57       374 iswprint
  4.06    0.019838          74       266 readdir64
  3.21    0.015652          69       224 strlen
...
------ ----------- ----------- --------- --------------------
100.00    0.488135                  3482 total

9.3. Additional Resources

For more information about ltrace and its features, see the resources listed below.

Installed Documentation

  • ltrace(1) — The manual page for the ltrace utility provides detailed information about its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man ltrace'

Online Documentation

  • ltrace for RHEL 6 and 7 — This article on the Red Hat Developer Blog offers additional in-depth information (including practical examples) on how to use ltrace for application debugging.

See Also

Chapter 10. memstomp

memstomp is a command line tool that can be used to identify function calls with overlapping memory regions in situations when such an overlap is not permitted by various standards. It intercepts calls to the library functions listed in Table 10.1, “Function Calls Inspected by memstomp” and for each memory overlap, it displays a detailed backtrace to help you debug the problem.

Similarly to Valgrind, the memstomp utility inspects applications without the need to recompile them. However, it is much faster than this tool and therefore serves as a convenient alternative to it.

Red Hat Developer Toolset is distributed with memstomp 0.1.5.

Table 10.1. Function Calls Inspected by memstomp

FunctionDescription

memcpy

Copies n bytes from one memory area to another and returns a pointer to the second memory area.

memccpy

Copies a maximum of n bytes from one memory area to another and stops when a certain character is found. It either returns a pointer to the byte following the last written byte, or NULL if the given character is not found.

mempcpy

Copies n bytes from one memory area to another and returns a pointer to the byte following the last written byte.

strcpy

Copies a string from one memory area to another and returns a pointer to the second string.

stpcpy

Copies a string from one memory area to another and returns a pointer to the terminating null byte of the second string.

strncpy

Copies a maximum of n characters from one string to another and returns a pointer to the second string.

stpncpy

Copies a maximum of n characters from one string to another. It either returns a pointer to the terminating null byte of the second string, or if the string is not null-terminated, a pointer to the byte following the last written byte.

strcat

Appends one string to another while overwriting the terminating null byte of the second string and adding a new one at its end. It returns a pointer to the new string.

strncat

Appends a maximum of n characters from one string to another while overwriting the terminating null byte of the second string and adding a new one at its end. It returns a pointer to the new string.

wmemcpy

The wide-character equivalent of the memcpy() function that copies n wide characters from one array to another and returns a pointer to the second array.

wmempcpy

The wide-character equivalent of the mempcpy() function that copies n wide characters from one array to another and returns a pointer to the byte following the last written wide character.

wcscpy

The wide-character equivalent of the strcpy() function that copies a wide-character string from one array to another and returns a pointer to the second array.

wcsncpy

The wide-character equivalent of the strncpy() function that copies a maximum of n wide characters from one array to another and returns a pointer to the second string.

wcscat

The wide-character equivalent of the strcat() function that appends one wide-character string to another while overwriting the terminating null byte of the second string and adding a new one at its end. It returns a pointer to the new string.

wcsncat

The wide-character equivalent of the strncat() function that appends a maximum of n wide characters from one array to another while overwriting the terminating null byte of the second wide-character string and adding a new one at its end. It returns a pointer to the new string.

10.1. Installing memstomp

In Red Hat Developer Toolset, the memstomp utility is provided by the devtoolset-8-memstomp package and is automatically installed with devtoolset-8-toolchain as described in Section 1.5, “Installing Red Hat Developer Toolset”.

10.2. Using memstomp

To run the memstomp utility on a program you want to analyze:

$ scl enable devtoolset-8 'memstomp program argument...'

To immediately terminate the analyzed program when a problem is detected, run the utility with the --kill (or -k for short) command line option:

$ scl enable devtoolset-8 'memstomp --kill program argument...'

The use of the --kill option is especially recommended if you are analyzing a multi-threaded program; the internal implementation of backtraces is not thread-safe and running the memstomp utility on a multi-threaded program without this command line option can therefore produce unreliable results.

Additionally, if you have compiled the analyzed program with the debugging information or this debugging information is available to you, you can use the --debug-info (or -d) command line option to produce a more detailed backtrace:

$ scl enable devtoolset-8 'memstomp --debug-info program argument...'

For detailed instructions on how to compile your program with the debugging information built in the binary file, see Section 7.2, “Preparing a Program for Debugging”. For information on how to install debugging information for any of the Red Hat Developer Toolset packages, see Section 1.5.4, “Installing Debugging Information”.

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset memstomp as default:

$ scl enable devtoolset-8 'bash'

Example 10.1. Using memstomp

In the current working directory, create a source file named employee.c with the following contents:

#include <stdio.h>
#include <string.h>

#define BUFSIZE 80

int main(int argc, char *argv[]) {
  char employee[BUFSIZE] = "John,Doe,john@example.com";
  char name[BUFSIZE] = {0};
  char surname[BUFSIZE] = {0};
  char *email;
  size_t length;

  /* Extract the information: */
  memccpy(name, employee, ',', BUFSIZE);
  length = strlen(name);
  memccpy(surname, employee + length, ',', BUFSIZE);
  length += strlen(surname);
  email = employee + length;

  /* Compose the new entry: */
  strcat(employee, surname);
  strcpy(employee, name);
  strcat(employee, email);

  /* Print the result: */
  puts(employee);

  return 0;
}

Compile this program into a binary file named employee:

$ scl enable devtoolset-8 'gcc -rdynamic -g -o employee employee.c'

To identify erroneous function calls with overlapping memory regions:

$ scl enable devtoolset-8 'memstomp --debug-info ./employee'
memstomp: 0.1.4 successfully initialized for process employee (pid 14887).

strcat(dest=0x7fff13afc265, src=0x7fff13afc269, bytes=21) overlap for employee(14887)
        ??:0    strcpy()
        ??:0    strcpy()
        ??:0    _Exit()
        ??:0    strcat()
        employee.c:26   main()
        ??:0    __libc_start_main()
        ??:0    _start()
John,john@example.comDoe,

10.3. Additional Resources

For more information about memstomp and its features, see the resources listed below.

Installed Documentation

  • memstomp(1) — The manual page for the memstomp utility provides detailed information about its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man memstomp'

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 7, GNU Debugger (GDB) — Instructions on debugging programs written in C, C++, and Fortran.
  • Chapter 8, strace — Instructions on using the strace utility to monitor system calls that a program uses and signals it receives.
  • Chapter 12, Valgrind — Instructions on using the Valgrind tool to profile applications and detect memory errors and memory management problems, such as the use of uninitialized memory, improper allocation and freeing of memory, and the use of improper arguments in system calls.

Part IV. Performance Monitoring Tools

Chapter 11. SystemTap

SystemTap is a tracing and probing tool that allows users to monitor the activities of the entire system without needing to instrument, recompile, install, and reboot. It is programmable with a custom scripting language, which gives it expressiveness (to trace, filter, and analyze) and reach (to look into the running kernel and applications).

SystemTap can monitor various types of events, such as function calls within the kernel or applications, timers, tracepoints, performance counters, and so on. Some included example scripts produce output similar to netstat, ps, top, and iostat, others include pretty-printed function callgraph traces or tools for working around security bugs.

Red Hat Developer Toolset is distributed with SystemTap 3.3. This version is more recent than the version included in the previous release of Red Hat Developer Toolset and provides numerous bug fixes and enhancements.

Table 11.1. Tools Distributed with SystemTap for Red Hat Developer Toolset

NameDescription

stap

Translates probing instructions into C code, builds a kernel module, and loads it into a running Linux kernel.

stapdyn

The Dyninst backend for SystemTap.

staprun

Loads, unloads, attaches to, and detaches from kernel modules built with the stap utility.

stapsh

Serves as a remote shell for SystemTap.

stap-prep

Determines and—if possible—downloads the kernel information packages that are required to run SystemTap.

stap-merge

Merges per-CPU files. This script is automatically executed when the stap utility is executed with the -b command line option.

stap-report

Gathers important information about the system for the purpose of reporting a bug in SystemTap.

stap-server

A compile server, which listens for requests from stap clients.

11.1. Installing SystemTap

In Red Hat Developer Toolset, SystemTap is provided by the devtoolset-8-systemtap package and is automatically installed with devtoolset-8-perftools as described in Section 1.5, “Installing Red Hat Developer Toolset”.

Note

The Red Hat Developer Toolset version of SystemTap is available for both Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7, but some new features are only offered by the Red Hat Developer Toolset version of SystemTap for Red Hat Enterprise Linux 7.

In order to place instrumentation into the Linux kernel, SystemTap may also require installation of additional packages with debugging information. To determine which packages to install, run the stap-prep utility as follows:

$ scl enable devtoolset-8 'stap-prep'

Note that if you execute this command as the root user, the utility automatically offers the packages for installation. For more information on how to install these packages on your system, see the Red Hat Enterprise Linux 6 SystemTap Beginners Guide or the Red Hat Enterprise Linux 7 SystemTap Beginners Guide.

11.2. Using SystemTap

To execute any of the tools that are part of SystemTap:

$ scl enable devtoolset-8 'tool option...'

See Table 11.1, “Tools Distributed with SystemTap for Red Hat Developer Toolset” for a list of tools that are distributed with SystemTap. For example, to run the stap tool to build an instrumentation module:

$ scl enable devtoolset-8 'stap option... argument...'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset SystemTap as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of SystemTap you are using at any point:

$ which stap

Red Hat Developer Toolset’s stap executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset SystemTap:

$ stap -V

11.3. Additional Resources

For more information about SystemTap and its features, see the resources listed below.

Installed Documentation

  • stap(1) — The manual page for the stap command provides detailed information on its usage, as well as references to other related manual pages. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man stap'
  • staprun(8) — The manual page for the staprun command provides detailed information on its usage. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man staprun'
  • SystemTap Tapset Reference ManualHTML documentation on the most common tapset definitions is located at /opt/rh/devtoolset-8/root/usr/share/doc/devtoolset-8-systemtap-client-2.8/index.html.

Online Documentation

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 12, Valgrind — Instructions on using the Valgrind tool to profile applications and detect memory errors and memory management problems, such as the use of uninitialized memory, improper allocation and freeing of memory, and the use of improper arguments in system calls.
  • Chapter 13, OProfile — Instructions on using the OProfile tool to determine which sections of code consume the greatest amount of CPU time and why.
  • Chapter 14, Dyninst — Instructions on using the Dyninst library to instrument a user-space executable.

Chapter 12. Valgrind

Valgrind is an instrumentation framework that ships with a number of tools for profiling applications. It can be used to detect various memory errors and memory-management problems, such as the use of uninitialized memory or an improper allocation and freeing of memory, or to identify the use of improper arguments in system calls. For a complete list of profiling tools that are distributed with the Red Hat Developer Toolset version of Valgrind, see Table 12.1, “Tools Distributed with Valgrind for Red Hat Developer Toolset”.

Valgrind profiles an application by rewriting it and instrumenting the rewritten binary. This allows you to profile your application without the need to recompile it, but it also makes Valgrind significantly slower than other profilers, especially when performing extremely detailed runs. It is therefore not suited to debugging time-specific issues, or kernel-space debugging.

Red Hat Developer Toolset is distributed with Valgrind 3.14.0. This version is more recent than the version included in the previous release of Red Hat Developer Toolset and provides numerous bug fixes and enhancements.

Table 12.1. Tools Distributed with Valgrind for Red Hat Developer Toolset

NameDescription

Memcheck

Detects memory management problems by intercepting system calls and checking all read and write operations.

Cachegrind

Identifies the sources of cache misses by simulating the level 1 instruction cache (I1), level 1 data cache (D1), and unified level 2 cache (L2).

Callgrind

Generates a call graph representing the function call history.

Helgrind

Detects synchronization errors in multithreaded C, C++, and Fortran programs that use POSIX threading primitives.

DRD

Detects errors in multithreaded C and C++ programs that use POSIX threading primitives or any other threading concepts that are built on top of these POSIX threading primitives.

Massif

Monitors heap and stack usage.

12.1. Installing Valgrind

In Red Hat Developer Toolset, Valgrind is provided by the devtoolset-8-valgrind package and is automatically installed with devtoolset-8-perftools.

For detailed instructions on how to install Red Hat Developer Toolset and related packages to your system, see Section 1.5, “Installing Red Hat Developer Toolset”.

Note

Note that if you use Valgrind in combination with the GNU Debugger, it is recommended that you use the version of GDB that is included in Red Hat Developer Toolset to ensure that all features are fully supported.

12.2. Using Valgrind

To run any of the Valgrind tools on a program you want to profile:

$ scl enable devtoolset-8 'valgrind --tool=tool program argument...'

See Table 12.1, “Tools Distributed with Valgrind for Red Hat Developer Toolset” for a list of tools that are distributed with Valgrind. The argument of the --tool command line option must be specified in lower case, and if this option is omitted, Valgrind uses Memcheck by default. For example, to run Cachegrind on a program to identify the sources of cache misses:

$ scl enable devtoolset-8 'valgrind --tool=cachegrind program argument...'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset Valgrind as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of Valgrind you are using at any point:

$ which valgrind

Red Hat Developer Toolset’s valgrind executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset Valgrind:

$ valgrind --version

12.3. Additional Resources

For more information about Valgrind and its features, see the resources listed below.

Installed Documentation

  • valgrind(1) — The manual page for the valgrind utility provides detailed information on how to use Valgrind. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man valgrind'
  • Valgrind DocumentationHTML documentation for Valgrind is located at /opt/rh/devtoolset-8/root/usr/share/doc/devtoolset-8-valgrind-3.13.0/html/index.html.

Online Documentation

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 10, memstomp — Instructions on using the memstomp utility to identify calls to library functions with overlapping memory regions that are not allowed by various standards.
  • Chapter 11, SystemTap — An introduction to the SystemTap tool and instructions on how to use it to monitor the activities of a running system.
  • Chapter 13, OProfile — Instructions on using the OProfile tool to determine which sections of code consume the greatest amount of CPU time and why.
  • Chapter 14, Dyninst — Instructions on using the Dyninst library to instrument a user-space executable.

Chapter 13. OProfile

OProfile is a low overhead, system-wide profiler that uses the performance-monitoring hardware on the processor to retrieve information about the kernel and executables on the system, such as when memory is referenced, the number of level 2 cache (L2) requests, and the number of hardware interrupts received. It consists of a configuration utility, a daemon for collecting data, and a number of tools that can be used to transform the data into a human-readable form. For a complete list of tools that are distributed with the Red Hat Developer Toolset version of OProfile, see Table 13.1, “Tools Distributed with OProfile for Red Hat Developer Toolset”.

OProfile profiles an application without adding any instrumentation by recording the details of every nth event. This allows it to consume fewer resources than Valgrind, but it also causes its samples to be less precise. Unlike Valgrind, which only collects data for a single process and its children in user-space, OProfile is well suited to collect system-wide data on both user-space and kernel-space processes, and requires root privileges to run.

Red Hat Developer Toolset is distributed with OProfile 1.3.0.

Table 13.1. Tools Distributed with OProfile for Red Hat Developer Toolset

NameDescription

operf

Records samples either for a single process or system-wide using the Linux Performance Events subsystem.

opannotate

Generates an annotated source file or assembly listing from the profiling data.

oparchive

Generates a directory containing executable, debug, and sample files.

opgprof

Generates a summary of a profiling session in a format compatible with gprof.

ophelp

Displays a list of available events.

opimport

Converts a sample database file from a foreign binary format to the native format.

opjitconv

Converts a just-in-time (JIT) dump file to the Executable and Linkable Format (ELF).

opreport

Generates image and symbol summaries of a profiling session.

ocount

A new tool for counting the number of times particular events occur during the duration of a monitored command.

13.1. Installing OProfile

In Red Hat Developer Toolset, OProfile is provided by the devtoolset-8-oprofile package and is automatically installed with devtoolset-8-perftools as described in Section 1.5, “Installing Red Hat Developer Toolset”.

13.2. Using OProfile

To run any of the tools that are distributed with OProfile:

# scl enable devtoolset-8 'tool option...'

See Table 13.1, “Tools Distributed with OProfile for Red Hat Developer Toolset” for a list of tools that are distributed with OProfile. For example, to use the ophelp command to list available events in the XML format:

$ scl enable devtoolset-8 'ophelp -X'

Note that you can execute any command using the scl utility, causing it to be run with the Red Hat Developer Toolset binaries used in preference to the Red Hat Enterprise Linux system equivalent. This allows you to run a shell session with Red Hat Developer Toolset OProfile as default:

$ scl enable devtoolset-8 'bash'
Note

To verify the version of OProfile you are using at any point:

$ which operf

Red Hat Developer Toolset’s operf executable path will begin with /opt. Alternatively, you can use the following command to confirm that the version number matches that for Red Hat Developer Toolset OProfile:

# operf --version

13.3. Additional Resources

For more information about OProfile and its features, see the resources listed below.

Installed Documentation

  • oprofile(1) — The manual page named oprofile provides an overview of OProfile and available tools. To display the manual page for the version included in Red Hat Developer Toolset:

    $ scl enable devtoolset-8 'man oprofile'
  • opannotate(1), oparchive(1), operf(1), opgprof(1), ophelp(1), opimport(1), opreport(1) — Manual pages for various tools distributed with OProfile provide more information on their respective usage. To display the manual page for the version included in Red Hat Developer Toolset:

    scl enable devtoolset-8 'man tool'

Online Documentation

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 11, SystemTap — An introduction to SystemTap and instructions on how to use it to monitor the activities of a running system.
  • Chapter 12, Valgrind — Instructions on using the Valgrind tool to profile applications and detect memory errors and memory management problems, such as the use of uninitialized memory, improper allocation and freeing of memory, and the use of improper arguments in system calls.
  • Chapter 14, Dyninst — Instructions on using the Dyninst library to instrument a user-space executable.

Chapter 14. Dyninst

The Dyninst library provides an application programming interface (API) for instrumenting and working with user-space executables during their execution. It can be used to insert code into a running program, change certain subroutine calls, or even remove them from the program. It serves as a valuable debugging and performance-monitoring tool. The Dyninst API is also commonly used along with SystemTap to allow non-root users to instrument user-space executables.

Red Hat Developer Toolset is distributed with Dyninst 9.3.2.

14.1. Installing Dyninst

In Red Hat Developer Toolset, the Dyninst library is provided by the devtoolset-8-dyninst package and is automatically installed with devtoolset-8-perftools as described in Section 1.5, “Installing Red Hat Developer Toolset”. In addition, it is recommended that you also install the GNU Compiler Collection provided by the devtoolset-8-toolchain package.

If you intend to write a custom instrumentation for binaries, install the relevant header files:

# yum install devtoolset-8-dyninst-devel

You can also install API documentation for this library:

# yum install devtoolset-8-dyninst-doc

For a complete list of documents that are included in the devtoolset-8-dyninst-doc package, see Section 14.3, “Additional Resources”. For detailed instructions on how to install optional packages to your system, see Section 1.5, “Installing Red Hat Developer Toolset”.

14.2. Using Dyninst

14.2.1. Using Dyninst with SystemTap

To use Dyninst along with SystemTap to allow non-root users to instrument user-space executables, run the stap command with the --dyninst (or --runtime=dyninst) command line option. This tells stap to translate a SystemTap script into C code that uses the Dyninst library, compile this C code into a shared library, and then load the shared library and run the script. Note that when executed like this, the stap command also requires the -c or -x command line option to be specified.

To use the Dyninst runtime to instrument an executable file:

$ scl enable devtoolset-8 "stap --dyninst -c 'command' option... argument..."

Similarly, to use the Dyninst runtime to instrument a user’s process:

$ scl enable devtoolset-8 "stap --dyninst -x process_id option... argument..."

See Chapter 11, SystemTap for more information about the Red Hat Developer Toolset version of SystemTap. For a general introduction to SystemTap and its usage, see the SystemTap Beginners Guide for Red Hat Enterprise Linux 6 or the SystemTap Beginners Guide for Red Hat Enterprise Linux 7.

Example 14.1. Using Dyninst with SystemTap

Consider a source file named exercise.C that has the following contents:

#include <stdio.h>

void print_iteration(int value) {
  printf("Iteration number %d\n", value);
}

int main(int argc, char **argv) {
  int i;
  printf("Enter the starting number: ");
  scanf("%d", &i);
  for(; i>0; --i)
    print_iteration(i);
  return 0;
}

This program prompts the user to enter a starting number and then counts down to 1, calling the print_iteration() function for each iteration in order to print the number to the standard output. Compile this program on the command line using the g++ compiler from Red Hat Developer Toolset:

$ scl enable devtoolset-8 'g++ -g -o exercise exercise.C'

Now consider another source file named count.stp with the following contents:

#!/usr/bin/stap

global count = 0

probe process.function("print_iteration") {
  count++
}

probe end {
  printf("Function executed %d times.\n", count)
}

This SystemTap script prints the total number of times the print_iteration() function was called during the execution of a process. Run this script on the exercise binary file:

$ scl enable devtoolset-8 "stap --dyninst -c './exercise' count.stp"
Enter the starting number: 5
Iteration number 5
Iteration number 4
Iteration number 3
Iteration number 2
Iteration number 1
Function executed 5 times.

14.2.2. Using Dyninst as a Stand-alone Library

Before using the Dyninst library as a part of your application, set the value of the DYNINSTAPI_RT_LIB environment variable to the path to the runtime library file:

$ export DYNINSTAPI_RT_LIB=/opt/rh/devtoolset-8/root/usr/lib64/dyninst/libdyninstAPI_RT.so

This sets the DYNINSTAPI_RT_LIB environment variable in the current shell session.

Example 14.2, “Using Dyninst as a Stand-alone Application” illustrates how to write and build a program to monitor the execution of a user-space process. For a detailed explanation of how to use Dyninst, see the resources listed in Section 14.3, “Additional Resources”.

Example 14.2. Using Dyninst as a Stand-alone Application

Consider the exercise.C source file from Example 14.1, “Using Dyninst with SystemTap”: this program prompts the user to enter a starting number and then counts down to 1, calling the print_iteration() function for each iteration in order to print the number to standard output.

Now consider another source file named count.C with the following contents:

#include <stdio.h>
#include <fcntl.h>
#include "BPatch.h"
#include "BPatch_process.h"
#include "BPatch_function.h"
#include "BPatch_Vector.h"
#include "BPatch_thread.h"
#include "BPatch_point.h"

void usage() {
  fprintf(stderr, "Usage: count <process_id> <function>\n");
}

// Global information for counter
BPatch_variableExpr *counter = NULL;

void createCounter(BPatch_process *app, BPatch_image *appImage) {
  int zero = 0;
  counter = app->malloc(*appImage->findType("int"));
  counter->writeValue(&zero);
}

bool interceptfunc(BPatch_process *app,
                   BPatch_image *appImage,
                   char *funcName) {
  BPatch_Vector<BPatch_function *> func;
  appImage->findFunction(funcName, func);
  if(func.size() == 0) {
    fprintf(stderr, "Unable to find function to instrument()\n");
    exit (-1);
  }
  BPatch_Vector<BPatch_snippet *> incCount;
  BPatch_Vector<BPatch_point *> *points;
  points = func[0]->findPoint(BPatch_entry);
  if ((*points).size() == 0) {
    exit (-1);
  }

  BPatch_arithExpr counterPlusOne(BPatch_plus, *counter, BPatch_constExpr(1));
  BPatch_arithExpr addCounter(BPatch_assign, *counter, counterPlusOne);

  return app->insertSnippet(addCounter, *points);
}

void printCount(BPatch_thread *thread, BPatch_exitType) {
  int val = 0;
  counter->readValue(&val, sizeof(int));
  fprintf(stderr, "Function executed %d times.\n", val);
}

int main(int argc, char *argv[]) {
   int pid;
   BPatch bpatch;
   if (argc != 3) {
     usage();
     exit(1);
   }
   pid = atoi(argv[1]);
   BPatch_process *app = bpatch.processAttach(NULL, pid);
   if (!app) exit (-1);
   BPatch_image *appImage = app->getImage();
   createCounter(app, appImage);
   fprintf(stderr, "Finding function %s(): ", argv[2]);
   BPatch_Vector<BPatch_function*> countFuncs;
   fprintf(stderr, "OK\nInstrumenting function %s(): ", argv[2]);
   interceptfunc(app, appImage, argv[2]);
   bpatch.registerExitCallback(printCount);
   fprintf(stderr, "OK\nWaiting for process %d to exit...\n", pid);
   app->continueExecution();
   while (!app->isTerminated())
     bpatch.waitForStatusChange();
   return 0;
}

Note that a client application is expected to destroy all Bpatch objects before any of the Dyninst library destructors are called. Otherwise the mutator might terminate unexpectedly with a segmentation fault. To work around this problem, set the BPatch object of the mutator as a local variable in the main() function. Or, if you need to use BPatch as a global variable, manually detach all the mutatee processes before the mutator exits.

This program accepts a process ID and a function name as command line arguments and then prints the total number of times the function was called during the execution of the process. You can use the following Makefile to build these two files:

DTS      = /opt/rh/devtoolset-4/root
CXXFLAGS = -g -I$(DTS)/usr/include/dyninst
LBITS   := $(shell getconf LONG_BIT)

ifeq ($(LBITS),64)
  DYNINSTLIBS = $(DTS)/usr/lib64/dyninst
else
  DYNINSTLIBS = $(DTS)/usr/lib/dyninst
endif

.PHONY: all
all: count exercise

count: count.C
	g++ $(CXXFLAGS) count.C -I /usr/include/dyninst -c
	g++ $(CXXFLAGS) count.o -L $(DYNINSTLIBS) -ldyninstAPI -o count

exercise: exercise.C
	g++ $(CXXFLAGS) exercise.C -o exercise

.PHONY: clean
clean:
	rm -rf *~ *.o count exercise

To compile the two programs on the command line using the g++ compiler from Red Hat Developer Toolset, run the make utility:

$ scl enable devtoolset-8 make
g++ -g -I/opt/rh/devtoolset-8/root/usr/include/dyninst count.C -c
g++ -g -I/opt/rh/devtoolset-8/root/usr/include/dyninst count.o -L /opt/rh/devtoolset-8/root/usr/lib64/dyninst -ldyninstAPI -o count
g++ -g -I/opt/rh/devtoolset-8/root/usr/include/dyninst exercise.C -o exercise

This creates new binary files called exercise and count in the current working directory.

In one shell session, execute the exercise binary file as follows and wait for it to prompt you to enter the starting number:

$ ./exercise
Enter the starting number:

Do not enter this number. Instead, start another shell session and type the following at its prompt to set the DYNINSTAPI_RT_LIB environment variable and execute the count binary file:

$ export DYNINSTAPI_RT_LIB=/opt/rh/devtoolset-8/root/usr/lib64/dyninst/libdyninstAPI_RT.so
$ ./count `pidof exercise` print_iteration
Finding function print_iteration(): OK
Instrumenting function print_iteration(): OK
Waiting for process 8607 to exit...

Now switch back to the first shell session and enter the starting number as requested by the exercise program. For example:

Enter the starting number: 5
Iteration number 5
Iteration number 4
Iteration number 3
Iteration number 2
Iteration number 1

When the exercise program terminates, the count program displays the number of times the print_iteration() function was executed:

Function executed 5 times.

14.3. Additional Resources

For more information about Dyninst and its features, see the resources listed below.

Installed Documentation

The devtoolset-8-dyninst-doc package installs the following documents in the /opt/rh/devtoolset-8/root/usr/share/doc/devtoolset-8-dyninst-doc-8.2.1/ directory:

  • Dyninst Programmer’s Guide — A detailed description of the Dyninst API is stored in the DyninstAPI.pdf file.
  • DynC API Programmer’s Guide — An introduction to DynC API is stored in the dynC_API.pdf file.
  • ParseAPI Programmer’s Guide — An introduction to the ParseAPI is stored in the ParseAPI.pdf file.
  • PatchAPI Programmer’s Guide — An introduction to PatchAPI is stored in the PatchAPI.pdf file.
  • ProcControlAPI Programmer’s Guide — A detailed description of ProcControlAPI is stored in the ProcControlAPI.pdf file.
  • StackwalkerAPI Programmer’s Guide — A detailed description of StackwalkerAPI is stored in the stackwalker.pdf file.
  • SymtabAPI Programmer’s Guide — An introduction to SymtabAPI is stored in the SymtabAPI.pdf file.
  • InstructionAPI Reference Manual — A detailed description of the InstructionAPI is stored in the InstructionAPI.pdf file.

For information on how to install this package on your system, see Section 14.1, “Installing Dyninst”.

Online Documentation

See Also

  • Chapter 1, Red Hat Developer Toolset — An overview of Red Hat Developer Toolset and more information on how to install it on your system.
  • Chapter 11, SystemTap — An introduction to SystemTap and instructions on how to use it to monitor the activities of a running system.
  • Chapter 12, Valgrind — Instructions on using the Valgrind tool to profile applications and detect memory errors and memory management problems, such as the use of uninitialized memory, improper allocation and freeing of memory, and the use of improper arguments in system calls.
  • Chapter 13, OProfile — Instructions on using the OProfile tool to determine which sections of code consume the greatest amount of CPU time and why.

Part V. Compiler Toolsets

Chapter 15. Compiler Toolsets documentation

The descriptions of the three compiler toolsets:

  • Clang and LLVM
  • Go
  • Rust

have been moved to a separate documentation set under Red Hat Developer Tools.

Part VI. Getting Help

Chapter 16. Accessing Red Hat Product Documentation

Red Hat Product Documentation located at https://access.redhat.com/site/documentation/ serves as a central source of information. It is currently translated in 23 languages, and for each product, it provides different kinds of books from release and technical notes to installation, user, and reference guides in HTML, PDF, and EPUB formats.

Below is a brief list of documents that are directly or indirectly relevant to this book.

Red Hat Developer Toolset

Red Hat Enterprise Linux

Chapter 17. Contacting Global Support Services

Unless you have a Self-Support subscription, when both the Red Hat Documentation website and Customer Portal fail to provide the answers to your questions, you can contact Global Support Services (GSS).

17.1. Gathering Required Information

Several items of information should be gathered before contacting GSS.

Background Information

Ensure you have the following background information at hand before calling GSS:

  • Hardware type, make, and model on which the product runs
  • Software version
  • Latest upgrades
  • Any recent changes to the system
  • An explanation of the problem and the symptoms
  • Any messages or significant information about the issue
Note

If you ever forget your Red Hat login information, it can be recovered at https://access.redhat.com/site/help/LoginAssistance.html.

Diagnostics

The diagnostics report for Red Hat Enterprise Linux is required as well. This report is also known as a sosreport and the program to create the report is provided by the sos package. To install the sos package and all its dependencies on your system:

# yum install sos

To generate the report:

# sosreport

For more information, access the Knowledgebase article at https://access.redhat.com/kb/docs/DOC-3593.

Account and Contact Information

In order to help you, GSS requires your account information to customize their support, as well contact information to get back to you. When you contact GSS ensure you have your:

  • Red Hat customer number or Red Hat Network (RHN) login name
  • Company name
  • Contact name
  • Preferred method of contact (phone or email) and contact information (phone number or email address)

Issue Severity

Determining an issue’s severity is important to allow the GSS team to prioritize their work. There are four levels of severity.

Severity 1 (urgent)
A problem that severely impacts your use of the software for production purposes. It halts your business operations and has no procedural workaround.
Severity 2 (high)
A problem where the software is functioning, but production is severely reduced. It causes a high impact to business operations, and no workaround exists.
Severity 3 (medium)
A problem that involves partial, non-critical loss of the use of the software. There is a medium to low impact on your business, and business continues to function by utilizing a workaround.
Severity 4 (low)
A general usage question, report of a documentation error, or a recommendation for a future product improvement.

For more information on determining the severity level of an issue, see https://access.redhat.com/support/policy/severity.

Once the issue severity has been determined, submit a service request through the Customer Portal under the Connect option, or at https://access.redhat.com/support/contact/technicalSupport.html. Note that you need your Red Hat login details in order to submit service requests.

If the severity is level 1 or 2, then follow up your service request with a phone call. Contact information and business hours are found at https://access.redhat.com/support/contact/technicalSupport.html.

If you have a premium subscription, then after hours support is available for Severity 1 and 2 cases.

Turn-around rates for both premium subscriptions and standard subscription can be found at https://access.redhat.com/support/offerings/production/sla.html.

17.2. Escalating an Issue

If you feel an issue is not being handled correctly or adequately, you can escalate it. There are two types of escalations:

Technical escalation
If an issue is not being resolved appropriately or if you need a more senior resource to attend to it.
Management escalation
If the issue has become more severe or you believe it requires a higher priority.

More information on escalation, including contacts, is available at https://access.redhat.com/support/policy/mgt_escalation.html.

17.3. Re-opening a Service Request

If there is more relevant information regarding a closed service request (such as the problem reoccurring), you can re-open the request via the Red Hat Customer Portal at https://access.redhat.com/support/policy/mgt_escalation.html or by calling your local support center, the details of which can be found at https://access.redhat.com/support/contact/technicalSupport.html.

Important

In order to re-open a service request, you need the original service-request number.

17.4. Additional Resources

For more information, see the resources listed below.

Online Documentation

Appendix A. Changes in Version 8.0

The sections below document features and compatibility changes introduced in Red Hat Developer Toolset 8.0.

A.1. Changes in GCC

Red Hat Developer Toolset 8.0 is distributed with GCC 8.2.1, which provides numerous enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of GCC included in Red Hat Developer Toolset 7.1:

  • The source code coverage analysis tool GCOV has been extended with various improvements.
  • New code generation options to increase program security such as -fstack-clash-protection have been added. Notably, the new -fcf-protection= option adds code instrumentation for checking target addresses of control-flow instructions. The possible values are full, branch, return, none.
  • Various new warnings to detect potentially buggy code with security implications have been added.
  • Front-end warnings have been improved to detect more bugs, and various warnings have been added.
  • Diagnostic messages have been improved.
  • The GCC sanitizers have been extended to detect more invalid cases. For instance, Address Sanitizer has gained two new options: -fsanitize=pointer-compare and -fsanitize=pointer-subtract, which warn about wrong code involving operations with pointers.

Language Features and Standards

  • Passing an empty class as an argument now takes up no space on the Intel64 and AMD 64 architectures, as required by the platform ABI. Passing or returning a class with only deleted copy and move constructors now uses the same calling convention as a class with a non-trivial copy or move constructor.
  • The value returned by the C++11 alignof operator has been corrected to match the C _Alignof operator and return minimum alignment, rather than the previously returned preferred alignment. To find the preferred alignment, use the GNU extension __alignof__ operator.
  • The default standard used when compiling code in the C language has changed to C17 with GNU extensions. This has the same effect as using the --std=gnu17 option.
  • The experimental capability for compiling C++ code using the C++17 standard has been improved, but it remains experimental and unstable. Compiling C++17 code is not forward or backward compatible with other versions of GCC, and is not supported.
  • Initial experimental capability for compiling C++ code using the future C++2A standard has been added.

Optimization Improvements

Improvements in optimization include these areas:

  • Interprocedural optimization
  • Profile-driven optimization
  • Link-time optimization
  • Optimization for loop nesting

Architecture support

  • Support for the Intel Cannonlake architecture has been added.
  • Tuning for the AMD Zen microarchitecture znver1 was improved.
  • Support for the Qualcomm Saphira CPU has been added.
  • Handling of the -march=native option on the ARM and 64-bit ARM architectures has been fixed.

Removed and Deprecated Features

  • Support for the Intel Cilk Plus extensions was removed.
  • Intel Memory Protection Extensions (MPX) are now deprecated.

A.2. Changes in GDB

Red Hat Developer Toolset 8.0 is distributed with GDB 8.2, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of GDB included in Red Hat Developer Toolset 7.1:

  • The --readnever option has been added to speed up startup in situations where symbolic debugging is not used. With this option, GDB does not read symbolic debug information from symbol files at startup.
  • GDB can now use the GNU MPFR library for correct evaluation of floating-point expressions when the architectures of debugging host and target systems are different. The library must be present in version 3.1 or higher.
  • GDB has been extended to access the guarded-storage-control registers and software based guarded-storage broadcast control registers on IBM z14 machines.
  • A new -a option has been added to the gcore command to dump all memory mappings.
  • Breakpoints on C++ functions are now set in all scopes by default. This means that the inputs are interpreted as potentially missing leading name space or class. To treat the inputs literally, use the new -q flag.

    As an example, running the break func() command will set a breakpoint on A::B::func() and B::func(). To match explicitly only the latter, run break -q B::func.

  • The ptype command now accepts a /o flag to print the offsets and sizes of data structure fields in a format similar the pahole tool output.
  • Breakpoints on functions with C++ ABI tags can now be specified without explicitly listing the tag.
  • GDB no longer considers int the type of variables and return type of functions, when debugging information is not available. As a consequence, you need to specify the types explicitly to call and print these.

New Commands

  • Set the current working directory for the debugging target with the new set cwd command. To display it, show cwd.
  • To start the debugging target and stop at the first instruction, use the new starti command.

Completion Improvements

  • Completion has been extended to understand context of the intended operation and provide more relevant results.
  • It is no longer necessary to use quotes for correct completion of function parameters in most situations.
  • Completion of identifiers under C++ anonymous namespaces has been improved.
  • Completion of label names has been added.

gdbserver Improvements

  • New set environment and unset environment commands have been added. With these commands, users can modify environment variables on the remote system before the debugging target is started. The remote system must be Unix-based.
  • gdbserver can now substitute variables and expand glob patterns in the debugging target command line options. This functionality is based on starting the target using a shell, which is the default behavior.
  • gdbserver has been extended to set the working directory of the debugging target process with the set cwd command.

A.3. Changes in binutils

Red Hat Developer Toolset 8.0 is distributed with binutils 2.30, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of binutils included in Red Hat Developer Toolset 7.1:

Assembler
  • A --generate-missing-build-notes [on|off] option has been added to control creation of GNU Build Attribute notes if none are present in the input sources.
  • Location views in DWARF debug line information are now supported.
  • Support for the WebAssembly file format, and conversion of WebAssembly to the wasm32 ELF file format have been added.
  • Support for building code for the Texas Instruments PRU processor has been added.
  • Support for the ARMv8-R architecture and Cortex-R52 processor has been added.
Linker
  • The -z separate-code and -z undefs options to generate a separate code PT_LOAD segment have been added. This improves security, but also increases the size of resulting executables. Note that by default, -z separate-code is enabled.
  • A -z globalaudit option has been addeed to force audit libraries to be run for every dynamic object loaded by an executable. In situations where the loader does not support this functionality, this has no effect.
  • Support for GNU Property notes which provide hints to the dynamic loader about the binary file has been added.
Other binary tools
  • The --debug-dump=links option has been added to the readelf tool to display the contents of any .gnu_debuglink or .gnu_debugaltlink sections present in the binary file. The same functionality has been added to the objdump tool with the new --dwarf=links option.
  • The readelf tool has been extended with the --debug-dump=follow-links option to follow indirect links into separate debug info files when dumping other DWARF sections. The same functionality has been added to the objdump tool with the new --dwarf=follow-links option.
  • The new --inlines option extends the existing --line-numbers option of the objdump tool to display nesting information for inlined functions.
  • The --merge-notes option has been added to the objcopy tool to reduce the size of notes in a binary file by merging and deleting redundant notes.
  • Support for locating separate debug info files using the build-id method has been added, where the separate file has a name based upon the build-id of the original file.

Changes Since Red Hat Enterprise Linux 7

The following features have been added since the release of binutils included in Red Hat Enterprise Linux 7, in addition to the changes listed above:

Assembler
  • Support for the RISC-V architecture has been added.
  • Support for the ARM Cortex-M23 and Cortex-M33 processors has been added.
Linker
  • The command line option --no-eh-frame-hdr can now be used in ELF-based linkers to disable the automatic generation of .eh_frame_hdr sections.
  • The --in-implib=<infile> option has been added to the ARM linker to enable specifying a set of Secure Gateway veneers that must exist in the output import library specified by the --out-implib=<outfile> option, and the address they must have. Note that --in-implib is only usable in combination with the --cmse-implib option.
  • The --out-implib=<file> option instructs the linker to generate an import library for an ELF executable, which can be used by another application to link against the executable. Previously, it was restricted to x86 PE targets. This option has been extended to work for any ELF based targets.
Other binary tools
  • The nm tool gained a new option --with-version-strings to display a symbol’s version information after the symbol’s name, if present.
  • The version of the objdump tool for ARC now accepts a -M option to specify multiple additional instruction classes to disassemble.
  • The --remove-section option of the objcopy and strip tools now accepts section patterns starting with an exclamation point (!) to indicate a non-matching section. Such non-matching section is removed from the set of sections matched by an earlier pattern indicated with the --remove-section option.
  • The --only-section option for the objcopy tool now accepts section patterns starting with an exclamation point (!) to indicate a non-matching section. Such non-matching section is removed from the set of sections matched by an earlier pattern indicated with the --only-section option.
  • A new --remove-relocations=SECTIONPATTERN option for the objcopy and strip tools. This option can be used to remove sections containing relocations. The SECTIONPATTERN is the section to which the relocations apply, not the relocation section itself.

A.4. Changes in elfutils

Red Hat Developer Toolset 8.0 is distributed with elfutils 0.174, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of elfutils included in Red Hat Developer Toolset 7.1:

  • Support for DWARF5 and split dwarf, including GNU DebugFission has been added:

    • The eu-readelf tools now accepts an --debug-dump=info+ option to show split unit DIEs/files.
    • The eu-readelf tools now accepts an --dwarf-skeleton=file option to associate an object file with the respective .dwo file.
    • The libdw library has been extended with the functions dwarf_die_addr_die(), dwarf_get_units(), dwarf_getabbrevattr_data(), and dwarf_cu_info().
  • When the debug alt file is not explicitly set with a call to dwarf_set_alt() in the libdw library, the library now will try to resolve it on first use.
  • Previously, the eu-readelf tool could show a variable with a negative value as if it had a large unsigned value, or show a large unsigned value as a negative value. This has been corrected and eu-readelf now looks up the size and signedness of constant value types to display them correctly.
  • A new function dwarf_next_lines() for reading .debug_line data lacking CU has been added to the libdw library. This function can be used as alternative to the dwarf_getsrclines() and dwarf_getsrcfiles() functions.
  • Previously, files with more than 65280 sections could cause errors in the the libelf and libdw libraries and all tools using them. This bug has been fixed. As a result, extended shnum and shstrndx values in ELF file headers are handled correctly.

A.5. Changes in OProfile

Red Hat Developer Toolset 8.0 is distributed with OProfile 1.3.0, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of OProfile included in Red Hat Developer Toolset 7.1:

  • Support for processors based on the Intel Goldmont Plus microarchitecture has been added.
  • OProfile recognition code has been fixed to properly recognize some models of IBM POWER9 processors
  • OProfile now works with Linux kernel version 4.14.

A.6. Changes in strace

Red Hat Developer Toolset 8.0 is distributed with strace 4.24, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of strace included in Red Hat Developer Toolset 7.1:

  • Several improvements to tracing of programs with a different personality (architecture) have been added.
  • Optional symbol demangling with the libiberty or libdw libraries has been added. To use this feature, add the -k option. To determine if this functionality is available, see output of the strace -V command.
  • Handling of multiple signal= specifications in an injection expression has changed and multiple specification now results in error.
  • A new -e trace=%pure option for tracing system calls with no arguments that never fail has been added.
  • Data are now always displayed for write system calls, regardless of success of these calls.
  • Delay injection has been added with the -e inject=SET:delay_enter= and -e inject=SET:delay_exit= options.
  • Injection of system calls with no side effects has been added as an alternative to injection of an invalid system calls. To do so, use the new -e inject=SET:system call= option.
  • The range of values allowed in the -e inject=…​:retval= option expression has been extended.
Decoding improvements and updates

Decoding of the following items has been added, improved or updated:

  • netlink protocols, messages and attributes
  • arch_prctl, bpf, getsockopt, io_pgetevent, kern_features, keyctl, prctl, ptrace, rseq, setsockopt, socket, statx and other system calls
  • Constants of various types
  • Path tracing for execveat, inotify_add_watch, inotify_init, select, symlink, symlinkat system calls and mmap system calls with indirect arguments
  • System calls specific to the ARM architectures __ARM_NR_*
  • Lists of signal codes

Additionally, commands for the ioctl system call have been updated to match Linux kernel version 4.17.

A.7. Changes in SystemTap

Red Hat Developer Toolset 8.0 is distributed with SystemTap 3.3, which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of SystemTap included in Red Hat Developer Toolset 7.1:

  • The --sysroot option has been optimized for cross-compiled environments.
  • A new --example option allows you to search the example scripts distributed with SystemTap without providing the whole path of the file.
  • Usage of SystemTap on systems with real time kernel or machines with a high number of CPUs has been improved.
  • Handling of code used for Spectre and Meltdown attack mitigation has been improved.

A.8. Changes in Valgrind

Red Hat Developer Toolset 8.0 is distributed with Valgrind 3.14.0 (pre-release), which provides a number of enhancements over the version included in the previous release of Red Hat Developer Toolset.

Changes Since Red Hat Developer Toolset 7.1

The following features have been added since the release of Valgrind included in Red Hat Developer Toolset 7.1:

  • A new --keep-debuginfo option has been added to enable retention of debug info for unloaded code. As a result, saved stack traces can include file and line information for code that is no longer present in memory.
  • Suppressions based on source file name and line number have been added.
  • The Helgrind tool has been extended with an option --delta-stacktrace to specify computation of full history stack traces. Notably, using this option together with --history-level=full can improve Helgrind performance by up to 25%.
  • False positive rate in the Memcheck tool for optimised code on the Intel and AMD 64-bit arcitectures and the ARM 64-bit architecture has been reduced. Note that you can use the --expensive-definedness-checks to control handling of definedness checks and improve the rate at the expense of performance.
  • Previously, the valgrind-devel package contained additional static libraries for building Valgrind tools. Because these tools are not supported, the package now only contains the header files needed for creating Valgrind-aware programs and libraries.

For more information about the new options and their known limitations, see the Valgrind(1) manual page.

Appendix B. Revision History

8.0-3

Tue 27 Nov 2018, Lenka Špačková (lspackova@redhat.com)

  • Release of Red Hat Developer Toolset 8.0 User Guide.
8.0-2

Tue 13 Nov 2018, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 8.0 User Guide.
8.0-1

Tue 23 Oct 2018, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 8.0 Beta User Guide.
7.0-8

Thu 03 May 2018, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 7.1 User Guide.
7.0-7

Wed 04 Apr 2018, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 7.1 Beta User Guide.
7.0-6

Tue 24 Oct 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 7.0 User Guide.
7.0-5

Tue 17 Oct 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release with minor fixes.
7.0-2

Tue 03 Oct 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 7.0 Beta User Guide.
6.1-3

Fri 26 May 2017, Vladimír Slávik (vslavik@redhat.com)

  • Clarified C++ compatibility information.
6.1-2

Wed 26 Apr 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 6.1 User Guide.
6.1-1

Wed 05 Apr 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release of Red Hat Developer Toolset 6.1 Beta User Guide.
6.0-9

Tue 04 Apr 2017, Lenka Špačková (lspackova@redhat.com)

  • Removed outdated information.
6.0-8

Fri 31 Mar 2017, Vladimír Slávik (vslavik@redhat.com)

  • Release with minor fixes.
6.0-7

Sun 13 Nov 2016, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 6.0 User Guide.
0.0-36

Tue 24 May 2016, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 4.1 User Guide.
0.0-33

Fri 13 Nov 2015, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 4.0 User Guide.
0.0-29

Wed 4 Nov 2015, Robert Krátký (rkratky@redhat.com)

  • Re-release of Red Hat Developer Toolset 4.0 Beta User Guide with a section on docker-formatted container images.
0.0-28

Wed 14 Oct 2015, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 4.0 Beta User Guide.
0.0-25

Thu 4 June 2015, Robert Krátký (rkratky@redhat.com)

  • Update to reflect RHSCL 2.0 GA.
0.0-23

Thu 23 Apr 2015, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.1 User Guide.
0.0-17

Tue 10 Mar 2015, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.1 Beta User Guide.
0.0-16

Thu 13 Nov 2014, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.0 User Guide with minor post-GA fixes.
0.0-14

Thu 30 Oct 2014, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.0 User Guide.
0.0-10

Tue 07 Oct 2014, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.0 Beta-2 User Guide.
0.0-8

Tue Sep 09 2014, Robert Krátký (rkratky@redhat.com)

  • Release of Red Hat Developer Toolset 3.0 Beta-1 User Guide.

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