AC_PROG_CC: how to distinguish clnag from gcc?

[Sébastien Hinderer]

Dear all,

It seems AC_PROG_CC wrongly believes clang is gcc and that may cause problems
when clang is passed a warning which is only supposrted by gcc, as is
the case e.g. for -Wno-stringop-truncation.

Is there a recommended way to determine for sure from a configure script
whether the detected C compiler is clang or gcc?

Thanks,

Sébastien.