LLVM Toolset is a Red Hat offering for developers on the Red Hat Enterprise Linux platform. It provides the LLVM compiler infrastructure framework, the Clang compiler for the C and C++ languages, the LLDB debugger, and related tools for code analysis.

LLVM Toolset is distributed as a part of Red Hat Developer Tools for Red Hat Enterprise Linux 7. LLVM Toolset is available as a module for Red Hat Enterprise Linux 8.

The following components are available as a part of LLVM Toolset:

LLVM Toolset is available for Red Hat Enterprise Linux 7 and Red Hat Enterprise Linux 8 on the following architectures:

This chapter lists the steps to perform before installing LLVM Toolset on a Red Hat Enterprise Linux 7 system. Complete the following steps to attach a subscription that provides access to the repository for Red Hat Developer Tools, and then enable the Red Hat Developer Tools and Red Hat Software Collections repositories.

Prerequisites

Procedure

Once the subscription is attached to the system and the repositories are enabled, install LLVM Toolset as described in Section 1.4, “Installing LLVM Toolset”.

Additional Resources

LLVM 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 Developer Tools content set is required in order to install LLVM Toolset on your Red Hat Enterprise Linux 7 system. For detailed instructions on how to associate your Red Hat Enterprise Linux 7 system with an appropriate subscription and get access to LLVM Toolset, see Section 1.3, “Getting access to LLVM Toolset on Red Hat Enterprise Linux 7”.

# yum install llvm-toolset-11.0-cmake llvm-toolset-11.0-cmake-doc

# yum install cmake cmake-doc

# yum install llvm-toolset-11.0-llvm-doc

# yum install llvm llvm-doc

A detailed description of LLVM Toolset and all its features is beyond the scope of this document. For more information, see the resources listed below.

Online documentation

To compile a C program to a binary file:

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

#include <stdio.h>

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

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 a C source file to an object 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:

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

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

When clang 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 the program:

$ ./file_name

$ ./hello
Hello, World!

A detailed description of the clang compiler and its features is beyond the scope of this document. For more information, see the resources listed below.

Installed documentation

Online documentation

See Also

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

This creates a binary file named output_file in the current working directory. If the -o option is omitted, the clang++ 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:

This creates an object file named object_file. If the -o option is omitted, the clang++ compiler creates a file named after the source file with the .o file extension.

To link object files together and create a binary file:

#include <iostream>

using namespace std;

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

When clang++ compiles a program, it creates an executable binary file. Change to the directory with the executable file and run this program:

./file_name

$ ./hello
Hello, World!

A detailed description of the clang compiler and its features is beyond the scope of this document. For more information, see the resources listed below.

Installed documentation

Online documentation

See Also

To compile a C or C++ program with debugging information that lldb can read, make sure the compiler you use is instructed to create debug information.

To run lldb on a program you want to debug:

This command starts lldb in an interactive mode and displays the default prompt, (lldb).

To quit the debugging session and return to the shell prompt, run the following command at any time:

(lldb) quit

#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;
}

Refer to Section 4.1, “Preparing a program for debugging” for information about controlling debug information using GCC or clang.

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

(lldb) list

As a result, the first ten lines of the source code are displayed.

To display the code from a particular line:

(lldb) list source_file_name:line_number

Additionally, lldb displays source code listing automatically in the following situations:

Setting a New Breakpoint

To set a new breakpoint at a certain line:

(lldb) breakpoint source_file_name:line_number

To set a breakpoint on a certain function:

(lldb) breakpoint source_file_name:function_name

(lldb) b 10
Breakpoint 1: where = fibonacci`main + 33 at fibonacci.c:10, address = 0x000000000040054e

(lldb)  breakpoint set -f fibonacci.c --line 10
Breakpoint 2: where = fibonacci`main + 33 at fibonacci.c:10, address = 0x000000000040054e

Listing Breakpoints

To display a list of currently set breakpoints:

(lldb) breakpoint list

(lldb) breakpoint list
Current breakpoints:
1: file = 'fibonacci.c', line = 10, exact_match = 0, locations = 1
  1.1: where = fibonacci`main + 33 at fibonacci.c:10, address = fibonacci[0x000000000040054e], unresolved, hit count = 0

2: file = 'fibonacci.c', line = 10, exact_match = 0, locations = 1
  2.1: where = fibonacci`main + 33 at fibonacci.c:10, address = fibonacci[0x000000000040054e], unresolved, hit count = 0

Deleting Existing Breakpoints

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

(lldb) breakpoint clear -f source_file_name -l line_number

(lldb) b 7
Breakpoint 3: where = fibonacci`main + 31 at fibonacci.c:9, address = 0x000000000040054c

(lldb) breakpoint clear -l 7 -f fibonacci.c
1 breakpoints cleared:
3: file = 'fibonacci.c', line = 7, exact_match = 0, locations = 1

To start an execution of the program you are debugging:

(lldb) run

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

(lldb) run argument …

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

(lldb) run
Process 21054 launched: 'fibonacci' (x86_64)
Process 21054 stopped
* thread #1, name = 'fibonacci', stop reason = breakpoint 1.1
    frame #0: fibonacci`main(argc=1, argv=0x00007fffffffdeb8) at fibonacci.c:10
   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;

The lldb tool enables you to display data relevant to the program state, including:

The common usage is to display the value of a variable. To display the current value of a certain variable:

(lldb) print variable_name

(lldb) print a
$0 = 0
(lldb) print b
$1 = 1

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

(lldb) continue

The execution stops again when it reaches another breakpoint.

To skip a certain number of breakpoints, typically when you are debugging a loop, run the continue command in the following form:

(lldb) continue -i number_of_breakpoints_to_skip

The lldb tool enables you to execute a single line of code from the current line pointer with step:

(lldb) step

To execute a certain number of lines:

(lldb) step -c number

(lldb) continue
Process 21580 resuming
Process 21580 stopped
* thread #1, name = 'fibonacci', stop reason = breakpoint 1.1
    frame #0: fibonacci`main(argc=1, argv=0x00007fffffffdeb8) at fibonacci.c:10
   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;

(lldb) step -c 3
Process 21580 stopped
* thread #1, name = 'fibonacci', stop reason = step in
    frame #0: fibonacci`main(argc=1, argv=0x00007fffffffdeb8) at fibonacci.c:11
   8
   9      while (b < LONG_MAX) {
   10       printf("%ld ", b);
-> 11       sum = a + b;
   12       a = b;
   13       b = sum;
   14     }

(lldb) print sum
$2 = 2

A detailed description of the lldb debugger and all its features is beyond the scope of this document. For more information, see the resources listed below.

Online documentation

See also

LLVM Toolset packages are part of the Red Hat Universal Base Images (UBIs) repositories. You need a set up UBI to access UBI repositories and build a container image of LLVM.

To set up a UBI, complete the following steps:

For more information on using UBI images, see Building, Running, and Managing Containers - Chapter 3, Working with Container Images.

FROM registry.access.redhat.com/ubi8/ubi:latest

RUN yum install -y llvm-toolset

RUN yum install clang

To set up a UBI, complete the following steps:

For more information on using UBI images, see Building, Running, and Managing Containers - Chapter 3, Working with Container Images.

FROM registry.access.redhat.com/ubi7/ubi:ilatest

RUN yum install -y llvm-toolset-${version}

RUN yum install llvm-toolset-${_version_}-clang