[Bug libstdc++/77459] [6/7 Regression] undefined reference to `snprintf' when building mingw-w64 cross-compiler

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77459

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to François Dumont from comment #6)
> Created attachment 39984 [details]
> Stop using __builtin_snprintf until __has_builtin is supported.
> 
> Could you try this patch ? Until we have __has_builtin support I propose to
> simulate __builtin_snprintf with __builtin_sprint.

This patch is wrong in several ways. GCC always supports __builtin_snprintf, so
even if we supported __has_builtin (which is "if" not "until") the test would
not be right. What happens when it's not supported by the target is a linker
error, not a missing builtin.

The patch adds complexity and pessimizes targets that do support snprintf.