Portable UNUSED parameter macro used on function signature for C and C++

Question

I\'m interested in creating a macro for eliminating the unused variable warning.

This question describes a way to suppress the unused parameter warning by writing a

Answer 1

Across many compilers I have used the following, excluding support for lint.

#if (__GNUC__ > 2) || (__GNUC__ == 2 && __GNUC_MINOR__ > 4)
#       define PGM_GNUC_UNUSED         __attribute__((__unused__))
#else
#       define PGM_GNUC_UNUSED
#endif

Tested compilers: GCC, Clang, EKOPath, Intel C Compiler / Composer XE, MinGW32 on Cygwin / Linux / MSYS, MinGW-w64 on Cygwin / Linux, Sun ONE Studio / Oracle Solaris Studio, Visual Studio 2008 / 2010.

Example usage:

pgm_tsc_init (
        PGM_GNUC_UNUSED pgm_error_t**   error
        )
{
...
}

PGM is the standard prefix for this C based project. GNUC is the convention from GLib for this attribute.

I think one compile warns about __attribute__ in certain circumstances but certainly no error.