Re: [PATCH 0/3] Use gnulib c-ctype module, not <ctype.h>

[Tom Tromey <tromey@adacore.com>]

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

Simon> My understanding is that poisoning using macros doesn't work, because it
Simon> interferes with identifiers of the same name in other headers.  But
Simon> would it be possible to do it using "#pragma GCC poison"?  Like:

I didn't try it but that's because I believe it won't work.

The pragma is better than the preprocessor approach, the manual says:

     If a poisoned identifier appears as part of the expansion of a
     macro which was defined before the identifier was poisoned, it will
     _not_ cause an error.  This lets you poison an identifier without
     worrying about system headers defining macros that use it.

However in our case the poisoning would likely occur before the
inclusion of the offending header.  The workaround would be to include
the locale (and maybe iostream?) headers everywhere, but I think we
definitely should not do that.

FTR the failure I saw (with cpp-style poisoning, a la safe-ctype.h) came
from source-cache.c which includes some locale stuff via <sstream>.

The main issue here is that the pragma works on an identifier basis but
really we'd like to be more selective and only exclude some particular
functions.

Tom