[Bug preprocessor/126929] unclear behavior of -std=c90 for the preprocessor

[vincent-gcc at vinc17 dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126929

--- Comment #1 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
A simpler test:

#include <limits.h>
#if ULONG_MAX + 1 == 0
#error "true"
#else
#error "false"
#endif

which should also give true in ISO C90.