6.1 Release Notes

Red Hat Developer Toolset 6.1

Release Notes for Red Hat Developer Toolset 6.1

Lenka Špačková

Red Hat Customer Content Services

Jaromír Hradílek

Red Hat Customer Content Services

Eliška Slobodová

Red Hat Customer Content Services

Abstract

Red Hat Developer Toolset is a Software Collection from the Red Hat Software Collections offering. It is designed for developers working on the Red Hat Enterprise Linux platform. Using a framework called Software Collections, an additional set of tools is installed into the /opt/ directory, as recommended by the UNIX Filesystem Hierarchy Standard. These tools are enabled by the user on demand using the supplied scl utility. Red Hat Developer Toolset 6.1 provides current versions of the GNU Compiler Collection, GNU Debugger, and other development, debugging, and performance monitoring tools. These do not replace the Red Hat Enterprise Linux system versions of these tools, nor will they be used in preference to those system versions unless explicitly invoked using the scl utility.
These Release Notes contain important information available at the time of release of Red Hat Developer Toolset 6.1. Known problems, resources, and other issues are discussed here. Read this document before beginning to use Red Hat Developer Toolset 6.1.
For information on other components of Red Hat Software Collections, see the Red Hat Software Collections Release Notes. For details about length of support for individual components, refer to the Red Hat Software Collections Product Life Cycle document.

Chapter 1.  System Requirements

This chapter specifies hardware requirements and contains information related to the installation of Red Hat Developer Toolset 6.1.

1.1. Installation Prerequisites

Red Hat Developer Toolset 6.1 contains packages for both Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 running on AMD64 and Intel 64 architectures. Generation and manipulation of 32-bit binaries is also supported.
Red Hat Developer Toolset 6.1 supports the following architectures on Red Hat Enterprise Linux 7:
  • The 64-bit ARM architecture (AArch64)
  • IBM POWER, big endian
  • IBM POWER, little endian
  • IBM z Systems
The correct packages must be installed according to the host operating system in use. Red Hat Enterprise Linux 6 RPM packages can be used only on supported versions of Red Hat Enterprise Linux 6, and Red Hat Enterprise Linux 7 RPM packages can be used only on supported versions of Red Hat Enterprise Linux 7.
Before installing Red Hat Developer Toolset 6.1, it is recommended to apply all available Red Hat Enterprise Linux errata updates. This will enable all Red Hat Developer Toolset features and apply fixes that can otherwise impact the tools or built code.
Red Hat Developer Toolset 6.1 requires systems to be subscribed to the Optional channel in order to access all the necessary dependent packages required by the Red Hat Developer Toolset toolchain. Packages from the Optional channel are listed in the Red Hat Software Collections 2.4 Release Notes.
If you use Red Hat Subscription Manager:
  • On Red Hat Enterprise Linux 6, select SystemAdministrationAdd/Remove Software from the panel and navigate to SystemSoftware Sources.
  • On Red Hat Enterprise Linux 7, you can add these repositories by navigating to ApplicationsSystem ToolsRed Hat Subscription Manager.
Then enable the Optional channel for your system. For detailed information, see https://access.redhat.com/solutions/392003.
Users of RHN Classic or Red Hat Satellite can enable the Optional channel by following the instructions at https://access.redhat.com/solutions/70019.
Since Red Hat Developer Toolset 4.1, the content is available also in the ISO format at https://access.redhat.com/downloads, specifically for Server and Workstation.

Note

Packages that require the Optional channel cannot be installed from the ISO image. A list of packages that require enabling of the Optional channel is provided in the Red Hat Software Collections Release Notes.
Beta content is unavailable in the ISO format.

1.2.  Installation and Upgrading

Use of Red Hat Developer Toolset 6.1 requires the removal of any earlier pre-release versions, including Beta releases. If you have installed any previous version of Red Hat Developer Toolset, uninstall it from your system as described in the Uninstalling Red Hat Developer Toolset section of the Red Hat Developer Toolset User Guide.
Note that installing Red Hat Developer Toolset 6.x in parallel with Red Hat Developer Toolset 4.x is supported.
For detailed information on installation of Red Hat Developer Toolset 6.1 see the Installing Red Hat Developer Toolset chapter of the Red Hat Developer Toolset User Guide.
The in-place upgrade from Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7 is not supported by Red Hat Developer Toolset. As a consequence, the installed components might not work correctly after the upgrade. If you want to upgrade from Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7, it is strongly recommended to remove all Red Hat Developer Toolset packages, perform the in-place upgrade, update the Red Hat Developer Toolset repository, and install the Red Hat Developer Toolset packages again. It is advisable to back up all data before upgrading.

Chapter 2.  Red Hat Developer Toolset 6.1 Release

This chapter serves as an overview of Red Hat Developer Toolset 6.1. It sums up its main features and changes, and provides a list of known issues.

2.1. Changes in Red Hat Developer Toolset 6.1

2.1.1. Upgraded Components

All components in Red Hat Developer Toolset 6.1 are shipped with the devtoolset-6- prefix.
The following components have been upgraded in Red Hat Developer Toolset 6.1 compared to the previous release of Red Hat Developer Toolset:
  • GCC to version 6.3.1
  • elfutils to version 0.168
  • GDB to version 7.12.1
Additionally, a bug fix update is available for ltrace.
For detailed information on changes in Red Hat Developer Toolset 6.1, see Red Hat Developer Toolset User Guide.

Note

The Eclipse component is shipped as a separate rh-eclipse46 Software Collection for Red Hat Enterprise Linux 7. For details, see the Red Hat Software Collections Release Notes.

2.1.2. Container Images

Red Hat Developer Toolset 6.1 includes two pre-built docker-formatted container images:
  • The rhscl/devtoolset-6-toolchain-rhel7 image, which contains the following Red Hat Developer Toolset components:
    • devtoolset-6-gcc
    • devtoolset-6-gcc-c++
    • devtoolset-6-gcc-fortran
    • devtoolset-6-gdb
  • The rhscl/devtoolset-6-perftools-rhel7 image, which contains the following components:
    • devtoolset-6-oprofile
    • devtoolset-6-systemtap
    • devtoolset-6-valgrind
    • devtoolset-6-dyninst
    • devtoolset-6-elfutils
The container images are available from the Red Hat Container Registry. For details on how to obtain the images and how to run Red Hat Developer Toolset components using these images, see Using Red Hat Software Collections Container Images.

2.2. Features

2.2.1. List of Components

Red Hat Developer Toolset 6.1 provides the following components:

Development Tools

  • GNU Compiler Collection (GCC)
  • binutils
  • elfutils
  • dwz
  • make

Debugging Tools

  • GNU Debugger (GDB)
  • strace
  • ltrace
  • memstomp

Performance Monitoring Tools

  • SystemTap
  • Valgrind
  • OProfile
  • Dyninst
For details, see the Red Hat Developer Toolset Components table in the Red Hat Developer Toolset User Guide.

2.2.2. Main Features

The Red Hat Developer Toolset 6.1 brings the following changes:
  • Red Hat Developer Toolset 6.1 adds support for Red Hat Enterprise Linux 6.9.
  • The Red Hat Developer Toolset version of the GNU Compiler Collection (GCC) has been upgraded to version 6.3.1 with many bug fixes.
  • The version of the GNU Debugger (GDB) included in Red Hat Developer Toolset provides several bug fixes.
  • The eu-readelf utility from package elfutils now allows showing just the symbol table of the given ELF section name instead of symbols from all symbol tables.
For a full list of changes and features introduced in this release, see Red Hat Developer Toolset User Guide.

2.3. Known Issues

gcc component, BZ#1433946
GCC in Red Hat Developer Toolset 3.x contained the libasan package, which might have conflicted with the system version of libasan. As a consequence, depending on which libasan was present in the system, the -fsanitize=address tool worked only either with the system GCC or with the Red Hat Developer Toolset version of GCC, but not with both at the same time. To prevent the described conflict, in Red Hat Developer Toolset 4.x and later versions, the package was renamed to libasanN, where N is a number. However, if the Red Hat Software Collections repository is enabled, the problem can occur after the system update because the system version of libasan is available in an earlier version than the Red Hat Developer Toolset 3.x version, which is still available in the repository. To work around this problem, exclude this package while updating:
~]$ yum update --exclude=libasan
gcc component, BZ#1378332
The libatomic library is unavailable for the 64-bit ARM architecture on Red Hat Enterprise Linux 7.2 and earlier versions. As a consequence, the devtoolset-6-libatomic-devel package cannot be installed on such systems. In Red Hat Enterprise Linux 7.3, the libatomic package for the 64-bit ARM architecture is shipped in the gcc-libraries package.
oprofile component
OProfile 1.1.0 shipped in Red Hat Developer Toolset 6.1 works on all supported architectures, with the exception of IBM z Systems, where only the ocount tool works on the following models: z196, zEC12, and z13. operf and the other tools, such as oparchive or opannotate, do not work on IBM z Systems. For profiling purposes, users are recommended to use the Red Hat Enterprise Linux 7 system OProfile 0.9.9 version, which supports opcontrol with TIMER software interrupts.
Note that for correct reporting of data collected by OProfile 0.9.9, the corresponding opreport utility is necessary. Thus opcontrol-based profiling should be performed with Red Hat Developer Toolset disabled because the reporting tools from Red Hat Developer Toolset cannot process data collected within opcontrol legacy mode correctly.
valgrind component, BZ#869184
The default Valgrind gdbserver support (--vgdb=yes) can cause certain register and flags values to be not always up-to-date due to optimizations done by the Valgrind core. The GDB utility is therefore unable to show certain parameters or variables of programs running under Valgrind. To work around this problem, use the --vgdb=full parameter. Note that programs might run slower under Valgrind when this parameter is used.
valgrind component, BZ#990931
Valgrind must be rebuilt without Red Hat Developer Toolset's GCC installed, or it will be used in preference to Red Hat Enterprise Linux system GCC. The binary files shipped by Red Hat are build using the system GCC. For any testing, Red Hat Developer Toolset's GDB should be used.
multiple components
The devtoolset-6-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 namely applies to devtoolset-6-gcc-debuginfo, devtoolset-6-ltrace-debuginfo, devtoolset-6-valgrind-debuginfo, and might apply to other debuginfo packages, too. A similar conflict can also occur in a multilib environment, where 64-bit debuginfo packages conflict with 32-bit debuginfo packages.
For example, on Red Hat Enterprise Linux 7, devtoolset-6-gcc-debuginfo conflicts with three packages: gcc-base-debuginfo, gcc-debuginfo, and gcc-libraries-debuginfo. On Red Hat Enterprise Linux 6, devtoolset-6-gcc-debuginfo conflicts with one package: gcc-libraries-debuginfo. As a consequence, if conflicting debuginfo packages are installed, attempts to install Red Hat Developer Toolset 6.1 can fail with a transaction check error message similar to the following examples:
file /usr/lib/debug/usr/lib64/libitm.so.1.0.0.debug from install of gcc-base-debuginfo-4.8.3-9.el7.x86_64 conflicts with file from package devtoolset-6-gcc-debuginfo-6.2.1-2.el7.x86_64
file /usr/lib/debug/usr/lib64/libtsan.so.0.0.0.debug from install of gcc-debuginfo-4.8.3-9.el7.x86_64 conflicts with file from package devtoolset-6-gcc-debuginfo-6.2.1-2.el7.x86_64
file /usr/src/debug/gcc-5.2.1-20150716/obj-x86_64-redhat-linux/x86_64-redhat-linux/libstdc++-v3/include/x86_64-redhat-linux/bits/c++config.h from install of gcc-libraries-debuginfo-5.2.1-2.1.el7.x86_64 conflicts with file from package devtoolset-6-gcc-debuginfo-6.2.1-2.el7.x86_64
file /usr/lib/debug/usr/lib64/libcilkrts.so.5.0.0.debug from install of gcc-libraries-debuginfo-4.9.0-6.1.1.el6.x86_64 conflicts with file from package devtoolset-6-gcc-debuginfo-6.2.1-2.el7.x86_64
To work around the problem, manually uninstall the conflicting debuginfo packages prior to installing Red Hat Developer Toolset 6.1. It is advisable to install only the relevant debuginfo packages when necessary and expect such problems to happen.

Other Notes

  • Red Hat Developer Toolset primarily aims to provide a compiler for development of user applications for deployment on multiple versions of Red Hat Enterprise Linux. Operating system components, kernel modules and device drivers generally correspond to a specific version of Red Hat Enterprise Linux, for which the supplied base OS compiler is recommended.
  • Red Hat Developer Toolset 6.1 supports only C, C++ and Fortran development. For other languages, invoke the system version of GCC available on Red Hat Enterprise Linux.
  • Building an application with Red Hat Developer Toolset 6.1 on Red Hat Enterprise Linux (for example, Red Hat Enterprise Linux 7) and then executing that application on an earlier minor version (such as Red Hat Enterprise Linux 6.6.z) may result in runtime errors due to differences in non-toolchain components between Red Hat Enterprise Linux releases. Users are advised to check compatibility carefully. Red Hat supports only execution of an application built with Red Hat Developer Toolset on the same, or a later, supported release of Red Hat Enterprise Linux than the version used to build that application.
  • All code in the non-shared library libstdc++_nonshared.a in Red Hat Developer Toolset 6.1 is licensed under the GNU General Public License v3 with additional permissions granted under Section 7, described in the GCC Runtime Library Exception version 3.1, as published by the Free Software Foundation.
  • The compiler included in Red Hat Developer Toolset emits newer DWARF debugging records than previous compilers available on Red Hat Enterprise Linux. These new debugging records improve the debugging experience in a variety of ways, particularly for C++ and optimized code. However, certain tools are not yet capable of handling the newer DWARF debug records. To generate the older style debugging records, use the options -gdwarf-2 -gstrict-dwarf or -gdwarf-3 -gstrict-dwarf.
  • Some newer 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 adds a small additional security risk because regular Red Hat Enterprise Linux errata would not change this code. If the need for developers to rebuild their applications due to such an issue arises, Red Hat will signal this in a security erratum. Developers are strongly advised not to statically link their entire application for the same reasons.
  • Note that error messages related to a missing libitm library when using the -fgnu-tm option require the libitm package to be installed. You can install the package with the following command:
    yum install libitm
  • To use the ccache utility with GCC included in Red Hat Developer Toolset, set your environment correctly. For example:
    ~]$ scl enable devtoolset-6 '/usr/lib64/ccache/gcc -c foo.c'
    Alternatively, you can create a shell with the Red Hat Developer Toolset version of GCC as the default compiler:
    ~]$ scl enable devtoolset-6 'bash'
    After you have created the shell, run the following two commands:
    ~]$ export PATH=/usr/lib64/ccache${PATH:+:${PATH}}
    ~]$ gcc -c foo.c
  • Because the elfutils libraries contained in Red Hat Developer Toolset 6.1 are linked to a client application statically, caution is advised when passing handles to libelf, libdw, and libasm data structures to external code and when passing handles received from external code to libelf, libdw, and libasm.
    Be especially careful when an external library, which is linked dynamically against the system version of elfutils, is passed a pointer to a structure that comes from the Red Hat Developer Toolset 6.1 version of elfutils (or vice versa).
    Generally, data structures used in the Red Hat Developer Toolset 6.1 version of elfutils are not compatible with the Red Hat Enterprise Linux system versions, and structures coming from one should never be touched by the other.
    In applications that use the Red Hat Developer Toolset 6.1 libraries, all code that was linked against the system version of the libraries should be recompiled against the libraries included in Red Hat Developer Toolset 6.1.
  • The elfutils EBL library, which is used internally by libdw, was amended not to open back ends dynamically. Instead, a selection of back ends is compiled in the library itself: the 32-bit AMD and Intel architecture, AMD64 and Intel 64 systems, Intel Itanium, IBM z Systems, 32-bit IBM Power Systems, 64-bit IBM Power Systems, IBM POWER, big endian, and the 64-bit ARM architecture. Some functionality may not be available if the client wishes to work with ELF files from architectures other than those mentioned above.
  • Some packages managed by the scl utility include privileged services that require sudo. The system sudo clears environment variables and so Red Hat Developer Toolset includes its own sudo shell script, wrapping scl enable. This script does not currently parse or pass normal sudo options, only sudo COMMAND ARGS .... In order to use the system version of sudo from within a Red Hat Developer Toolset-enabled shell, use the /usr/bin/sudo binary.
  • Red Hat Developer Toolset 6.1 includes GCC 6.2, which provides support for Cilk+, an extension to the C and C++ languages for parallel programming. A runtime library, libcilkrts, is included in this release to support the feature. The libcilkrts library will be a part of the gcc-libraries package in the future Red Hat Enterprise Linux releases but the package is not included in all supported Red Hat Enterprise Linux releases. To enable dynamic linkage of binaries and libraries built with Red Hat Developer Toolset 6.1 GCC using Cilk+ features on supported Red Hat Enterprise Linux releases that do not contain libcilkrts, install the libcilkrts.so shared library from Red Hat Developer Toolset 6.1 with such binaries or libraries.
  • Intel have issued erratum HSW136 concerning TSX (Transactional Synchronization Extensions) instructions. Under certain circumstances, software using the Intel TSX instructions may result in unpredictable behavior. TSX instructions may be executed by applications built with Red Hat Developer Toolset GCC under certain conditions. These include use of GCC's experimental Transactional Memory support (using the -fgnu-tm option) when executed on hardware with TSX instructions enabled. The users of Red Hat Developer Toolset are advised to exercise further caution when experimenting with Transaction Memory at this time, or to disable TSX instructions by applying an appropriate hardware or firmware update.
  • To use the Memory Protection Extensions (MPX) feature in GCC, the Red Hat Developer Toolset version of the libmpx library is required, otherwise the application might not link properly.
  • The two binutils linkers, gold and ld, have different ways of handling hidden symbols, which leads to incompatibilities in their behavior. Previously, the gold and ld linkers had inconsistent and incorrect behavior with regard to shared libraries and hidden symbols. There were two scenarios:
    • If a shared library referenced a symbol that existed elsewhere in both hidden and non-hidden versions, the gold linker produced a bogus warning message about the hidden version.
    • If a shared library referenced a symbol that existed elsewhere only as a hidden symbol, the gold linker created an executable, even though it could not work.
    The gold linker has been updated so that it no longer issues bogus warning messages about hidden symbols that also exist in a non-hidden version. The second scenario cannot be solved in the linker. It is up to the programmer to ensure that a non-hidden version of the symbol is available when the application is run.
    As a result, the two linkers' behavior is closer, but they still differ in case of a reference to a hidden symbol that cannot be found elsewhere in a non-hidden version. Unfortunately, there is not a single correct behavior for this situation, so the linkers are allowed to differ.
  • The valgrind-openmpi subpackage is no longer provided with Valgrind in Red Hat Developer Toolset. The devtoolset-<version>-valgrind-openmpi subpackages previously caused incompatibility issues with various Red Hat Enterprise Linux minor releases and problems with rebuilding. Users are recommended to use the latest Red Hat Enterprise Linux system version of the valgrind and valgrind-openmpi packages if they need to run Valgrind against their programs that are built against the openmpi-devel libraries.

Chapter 3. Additional Resources

For more information about Red Hat Developer Toolset 6.1 and Red Hat Enterprise Linux, see the resources listed below.

3.1. Red Hat Product Documentation

The Red Hat Documentation portal located at https://access.redhat.com/documentation/ serves as a central source of all product documentation. It is translated in 22 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.
The following is a brief list of documents that are directly or indirectly relevant to this book:
  • Red Hat Developer Toolset 6.1 User Guide — The User Guide for Red Hat Developer Toolset contains more information about installing and using this content set.
  • Red Hat Software Collections 2.4 Packaging Guide — The Packaging Guide for Red Hat Software Collections explains the concept of Software Collections, documents the scl utility, and provides a detailed explanation of how to create a custom Software Collection or extend an existing one.
  • Red Hat Software Collections 2.4 Release Notes — The Release Notes for Red Hat Software Collections document known problems, possible issues, and other important information available at the time of release of the content set. They also contain useful information on installing, rebuilding, migrating etc.
  • Using Red Hat Software Collections Container Images — This book provides information on how to use container images based on Red Hat Software Collections. The available container images include applications, daemons, databases, as well as the Red Hat Developer Toolset container images. The images can be run on Red Hat Enterprise Linux 7 Server and Red Hat Enterprise Linux Atomic Host.
  • Red Hat Enterprise Linux 6 Developer Guide — The Developer Guide for Red Hat Enterprise Linux 6 provides detailed information on compiling and building, debugging, and profiling.
  • Red Hat Enterprise Linux 7 Developer Guide — The Developer Guide for Red Hat Enterprise Linux 7 provides an introduction to application development tools in Red Hat Enterprise Linux 7.

3.2. Red Hat Developer Blog

Red Hat Developer Blog content is directed to designers and developers of applications based on Red Hat technologies. It contains links to product team blogs and other relevant internal and external resources. Its goal is to inform and engage the developer community with up-to-date information, best practices, opinion, product and program announcements as well as pointers to sample code and other resources.

3.3. Red Hat Developers Portal

Red Hat Developers Portal provides an overview of Red Hat Developer Toolset and offers getting started content, including Hello world! examples.

Appendix A. Revision History

Revision History
Revision 6.1-5Wed Apr 26 2017Lenka Špačková
Release of Red Hat Developer Toolset 6.1 Release Notes.
Revision 6.1-4Wed Apr 05 2017Lenka Špačková
Release of Red Hat Developer Toolset 6.1 Beta Release Notes.

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