Autoconf 2.59 breaks libstdc++ checks

[Andreas Schwab]

Gunther Nikl <gni@gecko.de> writes:

>   What about getc, putc and putchar from stdio?

The C standard says that they are functions.  The only difference to other
functions is that getc and putc are allowed to evaluate the second
argument twice when implemented as macro.  But they must still be
available as normal functions as well.

>   BTW, is it legal to implement these macros as functions using the macros
>   itself?
>
>     #include <stdio.h>
>     int (getc)(FILE *stream) { return getc(stream); }
>
>   This will break if getc isn't a macro.

Undefined behaviour.  You are not allowed to redefine standard functions.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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