Chapter 2. clang

In Clang and LLVM Toolset, clang is provided by the llvm-toolset-6.0-clang package and is automatically installed with the llvm-toolset-6.0 package. See Section 1.4, “Installing Clang and LLVM Toolset”.

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

scl enable llvm-toolset-6.0 'clang -o output_file source_file'

$ scl enable llvm-toolset-6.0 'clang -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 llvm-toolset-6.0 'clang -o object_file -c source_file'

$ scl enable llvm-toolset-6.0 'clang -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 llvm-toolset-6.0 'clang -o output_file object_file ...'

$ scl enable llvm-toolset-6.0 'clang -o output_file object_file ...'

Note that you can execute any command using the scl utility, causing it to be run with the Clang and LLVM Toolset binaries available. This allows you to run a shell session with Clang and LLVM Toolset clang directly available:

scl enable llvm-toolset-6.0 'bash'

$ scl enable llvm-toolset-6.0 'bash'

#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;
}

scl enable llvm-toolset-6.0 'clang -o hello hello.c'

$ scl enable llvm-toolset-6.0 'clang -o hello hello.c'

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

./hello

$ ./hello
Hello, World!

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

scl enable llvm-toolset-6.0 'clang++ -o output_file source_file ...'

$ scl enable llvm-toolset-6.0 'clang++ -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 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:

scl enable llvm-toolset-6.0 'clang++ -o object_file -c source_file'

$ scl enable llvm-toolset-6.0 'clang++ -o object_file -c source_file'

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:

scl enable llvm-toolset-6.0 'clang++ -o output_file object_file ...'

$ scl enable llvm-toolset-6.0 'clang++ -o output_file object_file ...'

Note that you can execute any command using the scl utility, causing it to be run with the Clang and LLVM Toolset binaries available. This allows you to run a shell session with Clang and LLVM Toolset clang directly available:

scl enable llvm-toolset-6.0 'bash'

$ scl enable llvm-toolset-6.0 'bash'

#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;
}

scl enable llvm-toolset-6.0 'clang++ -o hello hello.cpp'

$ scl enable llvm-toolset-6.0 'clang++ -o hello hello.cpp'

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

./hello

$ ./hello
Hello, World!

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

scl enable llvm-toolset-6.0 'clang option... -o object_file source_file'

$ scl enable llvm-toolset-6.0 'clang 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 Clang and LLVM Toolset binaries available. This allows you to run a shell session with Red LLVM Developer Toolset:

scl enable llvm-toolset-6.0 'bash'

$ scl enable llvm-toolset-6.0 'bash'

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

Online Documentation

See Also