How to test the current version of GCC at compile time?
Question
I would like to include a different file depending on the version of GCC. More precisely I want to write:
#if GCC_VERSION >= 4.2
# include <unordered_map>
# define EXT std
#elif GCC_VERSION >= 4
# include <tr1/unordered_map>
# define EXT std
#else
# include <ext/hash_map>
# define unordered_map __gnu_cxx::hash_map
# define EXT __gnu_cxx
#endif
I don't care about gcc before 3.2.
I am pretty sure there is a variable defined at preprocessing time for that, I just can't find it again.
Solution 2
Ok, after more searches, it one possible way of doing it is using __GNUC_PREREQ
defined in features.h
.
#ifdef __GNUC__
# include <features.h>
# if __GNUC_PREREQ(4,0)
// If gcc_version >= 4.0
# elif __GNUC_PREREQ(3,2)
// If gcc_version >= 3.2
# else
// Else
# endif
#else
// If not gcc
#endif
OTHER TIPS
There are a number of macros that should be defined for your needs:
__GNUC__ // major
__GNUC_MINOR__ // minor
__GNUC_PATCHLEVEL__ // patch
The version format is major.minor.patch, e.g. 4.0.2
The documentation for these can be found here.
As a side note:
To find all the predefined macros:
- Create empty file t.cpp
g++ -E -dM t.cpp
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