https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85995
--- Comment #4 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to jos...@codesourcery.com from comment #3)
> See trouble.texi, "Non-bugs" / "Certain Changes We Don't Want to Make",
> "Undefining @code{__STDC__} when @option{-ansi} is not used."
which answers my request.
Programmers normally use conditionals on '__STDC__' to ask whether
it is safe to use certain features of ISO C, such as function
prototypes or ISO token concatenation.
Precisely this is what I wish to do, with 2 versions of a macro: one that
assumes C conformance (requiring -fexcess-precision=standard with GCC, in
particular), and another one that doesn't but may be slower.
Since plain 'gcc' supports all the features of ISO C, the correct
answer to these questions is "yes".
This sentence is wrong by default, as it would imply
-fexcess-precision=standard!
