How to detect LLVM and its version through #define directives?

StackOverflow https://stackoverflow.com/questions/1617877

  •  06-07-2019
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Question

The question is quite clear I think. I'm trying to write a compiler detection header to be able to include in the application information on which compiler was used and which version.

This is part of the code I'm using:

/* GNU C Compiler Detection */
#elif defined __GNUC__
    #ifdef __MINGW32__
        #define COMPILER "MinGW GCC %d.%d.%d"
    #else
        #define COMPILER "GCC %d.%d.%d"
    #endif
    #define COMP_VERSION __GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__
#endif

Which could be used like this:

printf("  Compiled using " COMPILER "\n", COMP_VERSION);

Is there any way to detect LLVM and its version? And CLANG?

Was it helpful?

Solution

The __llvm__ and __clang__ macros are the official way to check for an LLVM compiler (llvm-gcc or clang) or clang, respectively.

__has_feature and __has_builtin are the recommended way of checking for optional compiler features when using clang, they are documented here.

Note that you can find a list of the builtin compiler macros for gcc, llvm-gcc, and clang using:

echo | clang -dM -E -

This preprocesses an empty string and spits out all macros defined by the compiler.

OTHER TIPS

I cannot find an answer here, only links to answers, so for completeness, here is the answer:

__clang__             // set to 1 if compiler is clang
__clang_major__       // integer: major marketing version number of clang
__clang_minor__       // integer: minor marketing version number of clang
__clang_patchlevel__  // integer: marketing patch level of clang
__clang_version__     // string: full version number

I get currently:

__clang__=1
__clang_major__=3
__clang_minor__=2
__clang_patchlevel__=0
__clang_version__="3.2 (tags/RELEASE_32/final)"

For clang, you shouldn't test its version number, you should check for features you want with feature checking macros.

Snippet from InitPreprocessor.cpp:

  // Compiler version introspection macros.
  DefineBuiltinMacro(Buf, "__llvm__=1");   // LLVM Backend
  DefineBuiltinMacro(Buf, "__clang__=1");  // Clang Frontend

  // Currently claim to be compatible with GCC 4.2.1-5621.
  DefineBuiltinMacro(Buf, "__GNUC_MINOR__=2");
  DefineBuiltinMacro(Buf, "__GNUC_PATCHLEVEL__=1");
  DefineBuiltinMacro(Buf, "__GNUC__=4");
  DefineBuiltinMacro(Buf, "__GXX_ABI_VERSION=1002");
  DefineBuiltinMacro(Buf, "__VERSION__=\"4.2.1 Compatible Clang Compiler\"");

I didn't find any way to get the version of llvm and clang itself, though..

Take a look at the Pre-defined Compiler Macros page, select Compilers->Clang. There is information on many other macros for standards, compilers, libraries, OS, architectures and more.

I agree that the best choice is to use has feature macroses, not version macroses. Example with boost:

#include <boost/config.hpp>

#if defined(BOOST_NO_CXX11_NOEXCEPT)
 #if defined(BOOST_MSVC)
  #define MY_NOEXCEPT throw()
 #else
  #define MY_NOEXCEPT
 #endif
#else
 #define MY_NOEXCEPT noexcept
#endif

void my_noexcept_function() MY_NOEXCEPT; // it's example, use BOOST_NOEXCEPT (:

But anyway, if you need compiler version, you can use boost.predef:

#include <iostream>
#include <boost/predef.h>

int main() {
#if (BOOST_COMP_CLANG)
  std::cout << BOOST_COMP_CLANG_NAME << "-" << BOOST_COMP_CLANG << std::endl;
#else
  std::cout << "Unknown compiler" << std::endl;
#endif
  return 0;
}

Output examples:

Clang-30400000
Clang-50000000

Note that if you're using llvm to hack on bytecode, and thus #includeing llvm include files, you can check the macros in llvm/Config/llvm-config.h. And concretely:

/* Major version of the LLVM API */
#define LLVM_VERSION_MAJOR 3

/* Minor version of the LLVM API */
#define LLVM_VERSION_MINOR 8

/* Patch version of the LLVM API */
#define LLVM_VERSION_PATCH 0

/* LLVM version string */
#define LLVM_VERSION_STRING "3.8.0"
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