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Using Clang and LLVM Toolset

Red Hat Developer Tools 2019.1

Installing and Using Clang and LLVM Toolset

Peter Macko

pmacko@redhat.com

Kevin Owen

Vladimir Slavik

Red Hat Developer Group Documentation Team devtools-docs@redhat.com

Legal Notice

Abstract

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

Chapter 1. Clang and LLVM Toolset
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1.1. About Clang and LLVM Toolset
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Clang and 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.

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

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

Expand

Table 1.1. Clang and LLVM Toolset Components
Name	Version	Description
`clang`	7.0.1	A LLVM compiler front-end for C and C++.
`lldb`	7.0.1	A C and C++ debugger using portions of LLVM.
`CMake`	3.6.2	A build management system.
`compiler-rt`	7.0.1	Runtime libraries for LLVM.
`llvm`	7.0.1	A collection of modular and reusable compiler and toolchain technologies.
`libomp`	7.0.1	A library for utilization of Open MP API specification for parallel programming.
`python-lit`	0.7.1	A Software testing tool for LLVM- and Clang-based test suites.

Note

Package versions are the same for Red Hat Enterprise Linux 7 and Red Hat Enterprise Linux 8.

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

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

1.3. Getting Access to Clang and LLVM Toolset on Red Hat Enterprise Linux 7
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Clang and LLVM Toolset is an offering that is distributed as a part of the Red Hat Developer Tools content set, which is available to customers with deployments of Red Hat Enterprise Linux 7. To install Clang and LLVM Toolset, enable the Red Hat Developer Tools and Red Hat Software Collections repositories by using the Red Hat Subscription Management and add the Red Hat Developer Tools GPG key to your system.

Enable the rhel-7-variant-devtools-rpms repository:
```
subscription-manager repos --enable rhel-7-variant-devtools-rpms
```
```
# subscription-manager repos --enable rhel-7-variant-devtools-rpms
```
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Replace variant with the Red Hat Enterprise Linux system variant (server or workstation).
Note
We recommend developers to use Red Hat Enterprise Linux Server for access to the widest range of development tools.
Enable the rhel-variant-rhscl-7-rpms repository:
```
subscription-manager repos --enable rhel-variant-rhscl-7-rpms
```
```
# subscription-manager repos --enable rhel-variant-rhscl-7-rpms
```
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Replace variant with the Red Hat Enterprise Linux system variant (server or workstation).

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

# 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

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Once the subscription is attached to the system and repositories enabled, you can install Red Hat Clang and LLVM Toolset as described in Section 1.4, “Installing Clang and LLVM Toolset”.

Additional Resources

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.
For detailed instructions on subscription to Red Hat Software Collections, see the Red Hat Developer Toolset User Guide, Section 1.4. Getting Access to Red Hat Developer Toolset.

1.4. Installing Clang and LLVM Toolset
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Clang and 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 Clang and 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 Clang and LLVM Toolset, see Section 1.3, “Getting Access to Clang and LLVM Toolset on Red Hat Enterprise Linux 7”.

Important

Before installing Clang and LLVM Toolset, install all available Red Hat Enterprise Linux updates.

Install all of the components included in Clang and LLVM Toolset for your operating system:
- On Red Hat Enterprise Linux 7, install the llvm-toolset-7.0 package:
  # yum install llvm-toolset-7.0
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- On Red Hat Enterprise Linux 8, install the llvm-toolset module:
  # yum module install llvm-toolset
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  This installs all development and debugging tools, and other dependent packages to the system.

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

Online Documentation

LLVM documentation overview — The official LLVM documentation.

Chapter 2. clang
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clang is a LLVM compiler front end for C-based languages: C, C++, Objective C/C++, OpenCL, and Cuda.

Clang and LLVM Toolset is distributed with clang 7.0.1.

2.1. Installing clang
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In Clang and LLVM Toolset on Red Hat Enterprise Linux 7, clang is provided by the llvm-toolset-7.0-clang package and is automatically installed with the llvm-toolset-7.0 package. On Red Hat Enterprise Linux 8, clang is provided by the llvm-toolset module. See Section 1.4, “Installing Clang and LLVM Toolset”.

2.2. Using clang
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Note

You can execute any command using the scl utility on Red Hat Enterprise Linux 7, causing it to be run with the Clang and LLVM Toolset binaries available. To use Clang and LLVM Toolset on Red Hat Enterprise Linux 7 without a need to use scl enable with every command, run a shell session with:

scl enable llvm-toolset-7.0 'bash'

$ scl enable llvm-toolset-7.0 'bash'

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2.2.1. Compiling a C Source File to a Binary File
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To compile a C program to a binary file:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang -o output_file source_file'

$ scl enable llvm-toolset-7.0 'clang -o output_file source_file'

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For Red Hat Enterprise Linux 8:
```
clang -o output_file source_file
```
```
$ clang -o output_file source_file
```
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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.

Example 2.1. Compiling a C Program with clang

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;
}

#include <stdio.h>

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

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Compile this source code on the command line by using the clang compiler from Clang and LLVM Toolset:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang -o hello hello.c'

$ scl enable llvm-toolset-7.0 'clang -o hello hello.c'

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For Red Hat Enterprise Linux 8:
```
clang -o hello hello.c
```
```
$ clang -o hello hello.c
```
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This creates a new binary file called hello in the current working directory.

2.2.2. Compiling a C Source File to an Object File
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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:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang -o object_file -c source_file'

$ scl enable llvm-toolset-7.0 'clang -o object_file -c source_file'

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For Red Hat Enterprise Linux 8:
```
clang -o object_file -c source_file
```
```
$ clang -o object_file -c source_file
```
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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.

2.2.3. Linking C Object files to a Binary File
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To link object files together and create a binary file:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang -o output_file object_file ...'

$ scl enable llvm-toolset-7.0 'clang -o output_file object_file ...'

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For Red Hat Enterprise Linux 8:
```
clang -o output_file object_file ...
```
```
$ clang -o output_file object_file ...
```
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Important

Certain more recent library features are statically linked into applications built with Clang and LLVM 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.

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

2.3. Running a C Program
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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

$ ./file_name

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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 with clang”, you can run it by typing the following command:

./hello

$ ./hello
Hello, World!

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2.4. Using clang++
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Note

scl enable llvm-toolset-7.0 'bash'

$ scl enable llvm-toolset-7.0 'bash'

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2.4.1. Compiling a C++ Source File to a Binary File
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To compile a C++ program on the command line, run the clang++ compiler as follows:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang++ -o output_file source_file ...'

$ scl enable llvm-toolset-7.0 'clang++ -o output_file source_file ...'

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For Red Hat Enterprise Linux 8:
```
clang++ -o output_file source_file ...
```
```
$ clang++ -o output_file source_file ...
```
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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.

2.4.2. Compiling a C++ Source File to an Object File
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To compile an object file on the command line:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang++ -o object_file -c source_file'

$ scl enable llvm-toolset-7.0 'clang++ -o object_file -c source_file'

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For Red Hat Enterprise Linux 8:
```
clang++ -o object_file -c source_file
```
```
$ clang++ -o object_file -c source_file
```
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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.

2.4.3. Linking C++ Object Files to a Binary File
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To link object files together and create a binary file:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang++ -o output_file object_file ...'

$ scl enable llvm-toolset-7.0 'clang++ -o output_file object_file ...'

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For Red Hat Enterprise Linux 8:
```
clang++ -o output_file object_file ...
```
```
$ clang++ -o output_file object_file ...
```
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Important

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

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;
}

#include <iostream>

using namespace std;

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

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Compile this source code on the command line by using the clang++ compiler from Clang and LLVM Toolset:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang++ -o hello hello.cpp'

$ scl enable llvm-toolset-7.0 'clang++ -o hello hello.cpp'

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For Red Hat Enterprise Linux 8:
```
clang++ -o hello hello.cpp
```
```
$ clang++ -o hello hello.cpp
```
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This creates a new binary file called hello in the current working directory.

2.5. Running a C++ Program
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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

./file_name

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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 by typing the following at a shell prompt:

./hello

$ ./hello
Hello, World!

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2.6. Using the clang Integrated Assembler
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To produce an object file from an assembly language program, run the clang tool as follows:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang option... -o object_file source_file'

$ scl enable llvm-toolset-7.0 'clang option... -o object_file source_file'

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For Red Hat Enterprise Linux 8:
```
clang option... -o object_file source_file
```
```
$ clang option... -o object_file source_file
```
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This creates an object file named object_file in the current working directory.

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

Installed Documentation

clang(1) — The manual page for the clang compiler provides detailed information on its usage; with few exceptions, clang++ accepts the same command line options as clang. To display the manual page for the version included in Clang and LLVM Toolset:
- For Red Hat Enterprise Linux 7:
  $ scl enable llvm-toolset-7.0 'man clang'
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- For Red Hat Enterprise Linux 8:
  $ man clang
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Online Documentation

clang — The clang compiler documentation provides detailed information on clang usage.

Chapter 3. lldb
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lldb is a command line tool you can use 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.

Clang and LLVM Toolset is distributed with lldb 7.0.1.

Note

scl enable llvm-toolset-7.0 'bash'

$ scl enable llvm-toolset-7.0 'bash'

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3.1. Installing lldb
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The lldb tool is provided by the llvm-toolset-7.0-lldb package and is automatically installed with the llvm-toolset-7.0 package. See Section 1.4, “Installing Clang and LLVM Toolset”.

3.2. Preparing a Program for Debugging
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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.

For instructions on suitably configuring clang, see the section Controlling Debug Information in Clang Compiler User’s Manual.
For instructions on suitably configuring GCC, see Red Hat Developer Toolset User Guide, Section 7.2. Preparing a Program for Debugging.

3.3. Running lldb
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To run lldb on a program you want to debug:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'lldb program_file_name'

$ scl enable llvm-toolset-7.0 'lldb program_file_name'

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For Red Hat Enterprise Linux 8:
```
lldb program_file_name
```
```
$ lldb program_file_name
```
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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

(lldb) quit

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Example 3.1. Running the lldb Utility on the fibonacci Binary File

Consider a C source file named fibonacci.c with the following content:

#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;
}

#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;
}

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Enable the debug information and compile the fibonacci.c with the following command:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'clang -g -o fibonacci fibonacci.c'

$ scl enable llvm-toolset-7.0 'clang -g -o fibonacci fibonacci.c'

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For Red Hat Enterprise Linux 8:
```
clang -g -o fibonacci fibonacci.c
```
```
$ clang -g -o fibonacci fibonacci.c
```
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Note

Refer to Section 3.2, “Preparing a Program for Debugging” for information about controlling debug information using GCC or clang.

Start debugging the program with lldb:

For Red Hat Enterprise Linux 7:

scl enable llvm-toolset-7.0 'lldb fibonacci'

$ scl enable llvm-toolset-7.0 'lldb fibonacci'
(lldb) target create "fibonacci"
Current executable set to 'fibonacci' (x86_64).
(lldb)

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For Red Hat Enterprise Linux 8:

lldb fibonacci

$ lldb fibonacci
(lldb) target create "fibonacci"
Current executable set to 'fibonacci' (x86_64).
(lldb)

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The output indicates that the program fibonacci is ready for debugging.

3.4. Listing Source Code
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To view the source code of the program you are debugging:

(lldb) list

(lldb) list

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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

(lldb) list source_file_name:line_number

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

Before you start the execution of the program you are debugging, lldb displays the first ten lines of the source code.
Each time the execution of the program is stopped, lldb displays the lines that surround the line on which the execution stops.

3.5. Using Breakpoints
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Setting a New Breakpoint

To set a new breakpoint at a certain line:

(lldb) breakpoint source_file_name:line_number

(lldb) breakpoint source_file_name:line_number

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To set a breakpoint on a certain function:

(lldb) breakpoint source_file_name:function_name

(lldb) breakpoint source_file_name:function_name

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Example 3.2. Setting a New Breakpoint

This example assumes that you have successfully compiled the fibonacci.c file as shown in Example 3.1, “Running the lldb Utility on the fibonacci Binary File”

Set two breakpoints at line 10 by running the following commands:

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

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

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(lldb)  breakpoint set -f fibonacci.c --line 10
Breakpoint 2: 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

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Note

In lldb, the command b is not an alias to breakpoint. You can use both commands to set breakpoints, but b uses a subset of the syntax supported by gdb’s break command, and breakpoint uses lldb syntax for setting breakpoints.

Listing Breakpoints

To display a list of currently set breakpoints:

(lldb) breakpoint list

(lldb) breakpoint list

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Example 3.3. Listing Breakpoints

This example assumes that you have successfully followed the instructions in Example 3.2, “Setting a New Breakpoint”.

Display the list of currently set breakpoints:

(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

(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

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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) breakpoint clear -f source_file_name -l line_number

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Example 3.4. Deleting an Existing Breakpoint

This example assumes that you have successfully compiled the fibonacci.c file.

Set a new breakpoint at line 7:

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

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

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Remove this breakpoint:

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

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

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3.6. Starting Execution
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To start an execution of the program you are debugging:

(lldb) run

(lldb) run

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

(lldb) run argument …

(lldb) run argument …

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

Example 3.5. Executing the fibonacci Binary File in lldb

This example assumes that you have successfully followed the instructions in Example 3.2, “Setting a New Breakpoint”.

Execute the fibonacci binary file in lldb:

(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;

(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;

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Execution of the program stops at the breakpoint set in Example 3.2, “Setting a New Breakpoint”.

3.7. Displaying Current Program Data
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The lldb tool enables you to display data relevant to the program state, including:

Variables of any complexity
Any valid expressions
Function call return values

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 variable_name

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Example 3.6. Displaying the Current Values of Variables

This example assumes that you have successfully followed the instructions in Example 3.5, “Executing the fibonacci Binary File in lldb”. Execution of the fibonacci binary stopped after reaching the breakpoint at line 10.

Display the current values of variables a and b:

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

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

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3.8. Continuing Execution after a Breakpoint
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To resume the execution of the program you are debugging after it reached a breakpoint:

(lldb) continue

(lldb) continue

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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

(lldb) continue -i number_of_breakpoints_to_skip

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Note

If the breakpoint is set on a loop, in order to skip the whole loop, you will have to set the number_of_breakpoints_to_skip to match the loop iteration count.

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

(lldb) step

(lldb) step

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To execute a certain number of lines:

(lldb) step -c number

(lldb) step -c number

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Toggle word wrap

Example 3.7. Continuing the Execution of the fibonacci Binary File after a Breakpoint

This example assumes that you have successfully followed the instructions in Example 3.5, “Executing the fibonacci Binary File in lldb”. The execution of the fibonacci binary stopped after reaching the breakpoint at line 10.

Resume the execution:

(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) 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;

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The execution stops the next time it reaches a breakpoint. (In this case it is the same breakpoint.) Execute the next three lines of code:

(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) 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     }

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Verify the current value of the sum variable:

(lldb) print sum
$2 = 2

(lldb) print sum
$2 = 2

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Toggle word wrap

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

Online Documentation

lldb Tutorial — The official lldb tutorial.
gdb to lldb command map — A list of GDB commands and their lldb equivalents.

Chapter 4. Container Image with Clang and LLVM Toolset for RHEL 7
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The Clang and LLVM Toolset is available as a container image which can be downloaded from Red Hat Container Registry.

4.1. Image Contents
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The devtools/llvm-toolset-7.0-rhel7 image provides content corresponding to the following packages:

Expand

Component	Version	Package
`LLVM`	7.0.1	llvm-toolset-7.0-llvm
`Clang`	7.0.1	llvm-toolset-7.0-clang
`LLDB`	7.0.1	llvm-toolset-7.0-lldb
`Runtime libraries`	7.0.1	llvm-toolset-7.0-compiler-rt
`Open MP library`	7.0.1	llvm-toolset-7.0-libomp
`CMake`	3.6.2	llvm-toolset-7.0-cmake
`python-lit`	0.7.1	llvm-toolset-7.0-python-lit

4.2. Access to the Image
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To pull the devtools/llvm-toolset-7.0-rhel7 image, run the following command as root:

podman pull registry.access.redhat.com/devtools/llvm-toolset-7.0-rhel7

# podman pull registry.access.redhat.com/devtools/llvm-toolset-7.0-rhel7

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4.3. Additional Resources
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Clang and LLVM Toolset 7.0.1 - entry in the Red Hat Container Catalog
Using Red Hat Software Collections Container Images

Chapter 5. Changes in Clang and LLVM Toolset in Red Hat Developer Tools 2019.1
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This chapter lists some notable changes in Clang and LLVM Toolset since its previous release.

5.1. LLVM
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LLVM has been updated from version 6.0.1 to 7.0.1.

For more information, see the LLVM 7.0.0 Release Notes.

5.2. clang
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clang has been updated from version 6.0.1 to 7.0.1.

For more information, see the Clang 7.0.0 Release Notes.

Legal Notice
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The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.

Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.

Red Hat, Red Hat Enterprise Linux, the Shadowman logo, the Red Hat logo, JBoss, OpenShift, Fedora, the Infinity logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.

Linux® is the registered trademark of Linus Torvalds in the United States and other countries.

Java® is a registered trademark of Oracle and/or its affiliates.

XFS® is a trademark of Silicon Graphics International Corp. or its subsidiaries in the United States and/or other countries.

MySQL® is a registered trademark of MySQL AB in the United States, the European Union and other countries.

Node.js® is an official trademark of Joyent. Red Hat is not formally related to or endorsed by the official Joyent Node.js open source or commercial project.

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All other trademarks are the property of their respective owners.

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Using Clang and LLVM Toolset

Installing and Using Clang and LLVM Toolset

Peter Macko

Kevin Owen

Vladimir Slavik

Chapter 1. Clang and LLVM ToolsetCopia collegamentoCollegamento copiato negli appunti!

1.1. About Clang and LLVM ToolsetCopia collegamentoCollegamento copiato negli appunti!

1.2. CompatibilityCopia collegamentoCollegamento copiato negli appunti!

1.3. Getting Access to Clang and LLVM Toolset on Red Hat Enterprise Linux 7Copia collegamentoCollegamento copiato negli appunti!

Additional Resources

1.4. Installing Clang and LLVM ToolsetCopia collegamentoCollegamento copiato negli appunti!

1.5. Additional ResourcesCopia collegamentoCollegamento copiato negli appunti!

Online Documentation

Chapter 2. clangCopia collegamentoCollegamento copiato negli appunti!

2.1. Installing clangCopia collegamentoCollegamento copiato negli appunti!

2.2. Using clangCopia collegamentoCollegamento copiato negli appunti!

2.2.1. Compiling a C Source File to a Binary FileCopia collegamentoCollegamento copiato negli appunti!

2.2.2. Compiling a C Source File to an Object FileCopia collegamentoCollegamento copiato negli appunti!

2.2.3. Linking C Object files to a Binary FileCopia collegamentoCollegamento copiato negli appunti!

2.3. Running a C ProgramCopia collegamentoCollegamento copiato negli appunti!

2.4. Using clang++Copia collegamentoCollegamento copiato negli appunti!

2.4.1. Compiling a C++ Source File to a Binary FileCopia collegamentoCollegamento copiato negli appunti!

2.4.2. Compiling a C++ Source File to an Object FileCopia collegamentoCollegamento copiato negli appunti!

2.4.3. Linking C++ Object Files to a Binary FileCopia collegamentoCollegamento copiato negli appunti!

2.5. Running a C++ ProgramCopia collegamentoCollegamento copiato negli appunti!

2.6. Using the clang Integrated AssemblerCopia collegamentoCollegamento copiato negli appunti!

2.7. Additional ResourcesCopia collegamentoCollegamento copiato negli appunti!

Installed Documentation

Online Documentation

See Also

Chapter 3. lldbCopia collegamentoCollegamento copiato negli appunti!

3.1. Installing lldbCopia collegamentoCollegamento copiato negli appunti!

3.2. Preparing a Program for DebuggingCopia collegamentoCollegamento copiato negli appunti!

3.3. Running lldbCopia collegamentoCollegamento copiato negli appunti!

3.4. Listing Source CodeCopia collegamentoCollegamento copiato negli appunti!

3.5. Using BreakpointsCopia collegamentoCollegamento copiato negli appunti!

Setting a New Breakpoint

Listing Breakpoints

Deleting Existing Breakpoints

3.6. Starting ExecutionCopia collegamentoCollegamento copiato negli appunti!

3.7. Displaying Current Program DataCopia collegamentoCollegamento copiato negli appunti!

3.8. Continuing Execution after a BreakpointCopia collegamentoCollegamento copiato negli appunti!

3.9. Additional ResourcesCopia collegamentoCollegamento copiato negli appunti!

Online Documentation

See Also

Chapter 4. Container Image with Clang and LLVM Toolset for RHEL 7Copia collegamentoCollegamento copiato negli appunti!

4.1. Image ContentsCopia collegamentoCollegamento copiato negli appunti!

4.2. Access to the ImageCopia collegamentoCollegamento copiato negli appunti!

4.3. Additional ResourcesCopia collegamentoCollegamento copiato negli appunti!

Chapter 5. Changes in Clang and LLVM Toolset in Red Hat Developer Tools 2019.1Copia collegamentoCollegamento copiato negli appunti!

5.1. LLVMCopia collegamentoCollegamento copiato negli appunti!

5.2. clangCopia collegamentoCollegamento copiato negli appunti!

Legal NoticeCopia collegamentoCollegamento copiato negli appunti!

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Chapter 1. Clang and LLVM Toolset
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1.1. About Clang and LLVM Toolset
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1.2. Compatibility
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1.3. Getting Access to Clang and LLVM Toolset on Red Hat Enterprise Linux 7
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1.4. Installing Clang and LLVM Toolset
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1.5. Additional Resources
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Chapter 2. clang
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2.1. Installing clang
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2.2. Using clang
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2.2.1. Compiling a C Source File to a Binary File
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2.2.2. Compiling a C Source File to an Object File
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2.2.3. Linking C Object files to a Binary File
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2.3. Running a C Program
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2.4. Using clang++
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2.4.1. Compiling a C++ Source File to a Binary File
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2.4.2. Compiling a C++ Source File to an Object File
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2.4.3. Linking C++ Object Files to a Binary File
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2.5. Running a C++ Program
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2.6. Using the clang Integrated Assembler
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2.7. Additional Resources
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Chapter 3. lldb
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3.1. Installing lldb
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3.2. Preparing a Program for Debugging
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3.3. Running lldb
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3.4. Listing Source Code
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3.5. Using Breakpoints
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3.6. Starting Execution
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3.7. Displaying Current Program Data
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3.8. Continuing Execution after a Breakpoint
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3.9. Additional Resources
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Chapter 4. Container Image with Clang and LLVM Toolset for RHEL 7
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4.1. Image Contents
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4.2. Access to the Image
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4.3. Additional Resources
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Chapter 5. Changes in Clang and LLVM Toolset in Red Hat Developer Tools 2019.1
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5.1. LLVM
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5.2. clang
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Legal Notice
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