AC_PROG_CC_C99 macro description is too vague / ambiguous

[Vincent Lefevre]

Hi,

The documentation of AC_PROG_CC_C99 is rather vague:

 -- Macro: AC_PROG_CC_C99
     If the C compiler is not in C99 mode by default, try to add an
     option to output variable `CC' to make it so.  This macro tries
     various options that select C99 on some system or another.  It
     considers the compiler to be in C99 mode if it handles `_Bool',
     `//' comments, flexible array members, `inline', signed and
     unsigned `long long int', mixed code and declarations, named
     initialization of structs, `restrict', `va_copy', varargs macros,
     variable declarations in `for' loops, and variable length arrays.

     After calling this macro you can check whether the C compiler has
     been set to accept C99; if not, the shell variable
     `ac_cv_prog_cc_c99' is set to `no'.

It is not clear whether GNU extensions are allowed or not. Even though
one may think that it is natural to keep the GNU extensions, gcc has
-std=c99 for strict ISO C99 (as opposed to gnu99 for the GNU dialect),
so that one can easily mix up "C99 mode" above and "c99 language" from
gcc. The macro description should avoid this possible confusion.

Thanks,

-- 
Vincent Lefèvre <address@hidden> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)