Re: Why AC_C_CHAR_UNSIGNED?

[Hallvard B Furuseth]

Ralf Wildenhues writes:
>> 2) If signedness of char has to be known during configure time
>> AC_C_CHAR_UNSIGNED is still useful.
>
> Exactly.  So the developer who decides that AC_C_CHAR_UNSIGNED is useful
> for him either cannot use autoconf -Wall any more, or is annoyed by the
> warning which is (then) wrong for him.  Since this warning hints at an
> optimization rather than at a potential bug, IMVHO here a wrong warning
> is worse than no warning.

Well, it is a _potential_ bug in code which uses of the C macro defined
by AC_C_CHAR_UNSIGNED, though hopefully an unlikely one.  The reason I
reacted to this in the first place was not that it can be "optimized"
away, but that the macro invades the C implementation's namespace.  Some
implementation could e.g. define __CHAR_UNSIGNED__ as a boolean - 0 for
signed, 1 for unsigned.  That's different from the autoconf macros that
e.g. #define const if missing, in the hope of compiling ISO C-like code
on non-ISO C compilers.

-- 
Hallvard