Re: [lmi] xanadu/remove-ISOC99_SOURCE-def

[Vadim Zeitlin]

On Sun, 22 May 2022 15:45:30 +0000 Greg Chicares <gchicares@sbcglobal.net> 
wrote:

GC> I haven't applied this:
GC> 
GC> -// This selects a correct snprintf() for MinGW-w64.
GC> -
GC> -#if defined __GNUC__
GC> -#   if !defined _ISOC99_SOURCE
GC> -#       define _ISOC99_SOURCE
GC> -#   endif // !defined _ISOC99_SOURCE
GC> -#endif // defined __GNUC__
GC> 
GC> because, for the historical libmingwex at least,
GC> some macro such as _ISOC99_SOURCE was required to
GC> override a defective msvcrt snprintf(). IIRC, some
GC> other macros served the same purpose; this one
GC> seemed the least objectionable.
GC> 
GC> Do you know for sure that the MinGW-w64 project
GC> has made that replacement unconditional?

 No, they haven't, there is still a complicated conditional checking for,
among other things, _ISOC99_SOURCE, before defining __USE_MINGW_ANSI_STDIO
in _mingw.h (located in /usr/x86_64-w64-mingw32/include on Debian systems).

 However this condition also contains the following subexpression:

     || (defined (__cplusplus) && __cplusplus >= 201103L && __MSVCRT_VERSION__ 
< 0xE00) \

which seems to indicate that it's not needed to enable MinGW own
implementation when using MSVC CRT >= 1400 (which will always be the case
nowadays), which has a (more) standard compliant snprintf() of its own.

 I also hoped that if there were any problems with using that snprintf(),
they would be uncovered by the unit tests, notably snprintf_test.cpp, but
it passes without problems.

 So I think it should be safe to remove it. BTW, if we you don't want to do
it, I think it would be better to predefine __USE_MINGW_ANSI_STDIO itself
(which wouldn't help the clang-tidy check, of course, but this is unrelated
to it) rather than doing it indirectly via _ISOC99_SOURCE.

 Regards,
VZ

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