https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126929
Bug ID: 126929
Summary: unclear behavior of -std=c90 for the preprocessor
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: vincent-gcc at vinc17 dot net
Target Milestone: ---
When I compile the following code
#include <limits.h>
#if ULONG_MAX >= 0xffffffffffffffff
#error "true"
#else
#error "false"
#endif
with "gcc -c -std=c90 -m32" under Linux x86_64, I get the error on #error
"false".
In ISO C90, the preprocessor arithmetic is long or unsigned long, so that with
the 32-bit ABI, the test ULONG_MAX >= ... would always be true, and I would
expect the error on #error "true".
It is not clear whether the obtained result is incorrect, i.e. whether the -std
option affects the preprocessor. The GCC man page and manual say that -std=
determines the language standard (or dialect). But the behavior of the
preprocessor is part of the language standard. So this should be fixed and/or
clarified.
