Determine LLVM versus GCC at compile time

Question

I'm trying to write a macro similar to the following:

#ifndef DEPRECATED_ATTRIBUTE_MESSAGE
  #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated (message)))
#endif

And this works, but only with the Apple LLVM 3.0 compiler. It breaks at compile time for anything else meaning I have to strip it down to

#ifndef DEPRECATED_ATTRIBUTE_MESSAGE
  #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated))
#endif

which is much less useful.

My question:

I think the solution is to apply some macro to identify the version of the compiler at compile time. Is there a way to identify the Apple LLVM 3.0 compiler versus LLVM GCC 4.2 or GCC 4.2 (or anything else)?

Ideally, I'd like to work out something like this, but I can't find the right macro to figure it out:

#ifdef [Apple LLVM 3.0]
  #ifndef DEPRECATED_ATTRIBUTE_MESSAGE
    #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated (message)))
  #endif
#else
  #ifndef DEPRECATED_ATTRIBUTE_MESSAGE
    #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated))
  #endif
#endif

score 4 · Accepted Answer · 2011-09-14T16:04:38.807

It should work with Clang’s feature checking macros:

// In case the compiler/preprocessor doesn't support __has_extension
#ifndef __has_feature         // Optional of course.
  #define __has_feature(x) 0  // Compatibility with non-clang compilers.
#endif
#ifndef __has_extension
  #define __has_extension __has_feature // Compatibility with pre-3.0 compilers.
#endif    

#if __has_extension(attribute_deprecated_with_message)
  #ifndef DEPRECATED_ATTRIBUTE_MESSAGE
    #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated (message)))
  #endif
#else
  #ifndef DEPRECATED_ATTRIBUTE_MESSAGE
    #define DEPRECATED_ATTRIBUTE_MESSAGE(message) __attribute__((deprecated))
  #endif
#endif

score 1 · Answer 2 · answered Sep 14 '11 at 16:01

1

Apple LLVM compiler defines __clang__.

answered Sep 14 '11 at 16:01

servn

3,049
14
8

Clang defines `__clang__`, but `llvm-gcc` unfortunately does not. Does anybody know how to distinguish `gcc`from `llvm-gcc`? The reason I need this, is that `llvm-gcc` has some important differences. For example, `llvm-gcc` 4.2 does not define `__GXX_RTTI` when `gcc` does. – Kristian Spangsege Oct 16 '12 at 19:32
1

Here is the answer: `llvm-gcc` defines `__llvm__`. – Kristian Spangsege Oct 16 '12 at 19:36
The fact that `llvm-gcc-4.2` doesn't define `__GXX_RTTI` has nothing to do with the fact that it uses LLVM; that's just how gcc 4.2 behaves. – servn Oct 17 '12 at 04:02
Are you saying that gcc 4.2 also does not define __GXX_RTTI? I assumed it did. – Kristian Spangsege Oct 18 '12 at 12:02
gcc 4.2 does not define __GXX_RTTI. – servn Oct 20 '12 at 03:32

Determine LLVM versus GCC at compile time

2 Answers2