What are the gcc preprocessor flags for the compiler's version number?

Question

I have run into a bug with gcc v3.4.4 and which to put an #ifdef in my code to work around the bug for only that version of the compiler.

What are the GCC compiler preprocessor flags to detect the version number of the compiler?

Thanks.

Answer 1

__GNUC__, __GNUC_MINOR__ and __GNUC_PATCHLEVEL__.

For instance, GCC 4.0.1 will do:

#define __GNUC__ 4
#define __GNUC_MINOR__ 0
#define __GNUC_PATCHLEVEL__ 1

Here is a little command line that is nice to remember when you are wondering which are the predefined preprocessor directives defined by the GNU GCC compiler under your current programming environment:

gcc -E -dM - < /dev/null |less

Answer 2

Suprisingly enough, __VERSION__. For my copy of g++ 4.4.1, this produces the string "4.4.1"

Answer 3

From the online docs:

__GNUC__
__GNUC_MINOR__
__GNUC_PATCHLEVEL__
These macros are defined by all GNU compilers that use the C preprocessor: C, C++, Objective-C and Fortran. Their values are the major version, minor version, and patch level of the compiler, as integer constants. For example, GCC 3.2.1 will define __GNUC__ to 3, __GNUC_MINOR__ to 2, and __GNUC_PATCHLEVEL__ to 1. These macros are also defined if you invoke the preprocessor directly.

and

__VERSION__
This macro expands to a string constant which describes the version of the compiler in use. You should not rely on its contents having any particular form, but it can be counted on to contain at least the release number.

Answer 4

From the gnu cpp manual...

---

__GNUC__
__GNUC_MINOR__
__GNUC_PATCHLEVEL__

These macros are defined by all GNU compilers that use the C preprocessor: C, C++, Objective-C and Fortran. Their values are the major version, minor version, and patch level of the compiler, as integer constants. For example, GCC 3.2.1 will define __GNUC__ to 3, __GNUC_MINOR__ to 2, and __GNUC_PATCHLEVEL__ to 1. These macros are also defined if you invoke the preprocessor directly.

__GNUC_PATCHLEVEL__ is new to GCC 3.0; it is also present in the widely-used development snapshots leading up to 3.0 (which identify themselves as GCC 2.96 or 2.97, depending on which snapshot you have).

If all you need to know is whether or not your program is being compiled by GCC, or a non-GCC compiler that claims to accept the GNU C dialects, you can simply test __GNUC__. If you need to write code which depends on a specific version, you must be more careful. Each time the minor version is increased, the patch level is reset to zero; each time the major version is increased (which happens rarely), the minor version and patch level are reset. If you wish to use the predefined macros directly in the conditional, you will need to write it like this:

          /* Test for GCC > 3.2.0 */
          #if __GNUC__ > 3 || \
              (__GNUC__ == 3 && (__GNUC_MINOR__ > 2 || \
                                 (__GNUC_MINOR__ == 2 && \
                                  __GNUC_PATCHLEVEL__ > 0))

Answer 5

There's 3 macros for the gcc version you can test on.

__GNUC_MINOR__ 
 __GNUC_PATCHLEVEL__ 
 __GNUC__

e.g. my gcc v 4.3.1 defines them as such:

#define __GNUC_MINOR__ 1
#define __GNUC_PATCHLEVEL__ 3
#define __GNUC__ 4

You can see the "buitin" macros defined by running

gcc -E -dM -x c /dev/null