https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103123
Bug ID: 103123
Summary: incorrect or misleading warning "floating constant
exceeds range of ..." in ISO C11 and C17
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: vincent-gcc at vinc17 dot net
Target Milestone: ---
On the C code
#if __STDC__ == 1 && __STDC_VERSION__ >= 201710 && defined(__STDC_IEC_559__)
double foo (void)
{
return 1.0e999;
}
#endif
I get the following warning:
tst.c: In function 'foo':
tst.c:4:3: warning: floating constant exceeds range of 'double' [-Woverflow]
4 | return 1.0e999;
| ^~~~~~
Tested version:
gcc (Debian 20210918-1) 12.0.0 20210918 (experimental) [master
r12-3644-g7afcb534239]
However, the C11 committee draft N1570 and C17 ballot N2176 say in 5.2.4.2.2p5:
"The minimum range of representable values for a floating type is the most
negative finite floating-point number representable in that type through the
most positive finite floating-point number representable in that type. In
addition, if negative infinity is representable in a type, the range of that
type is extended to all negative real numbers; likewise, if positive infinity
is representable in a type, the range of that type is extended to all positive
real numbers."
Note: The C2x draft N2731 says the same thing.
So, since __STDC_IEC_559__ is defined, there is a negative and a positive
infinity for the double type, and 5.2.4.2.2p5 implies that the range is the
whole set of real numbers. In particular, it includes the constant 1.0e999
above, so that the warning is incorrect, or at least misleading.
