https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110476
Bug ID: 110476
Summary: constexpr floating point regression with -std=c++XX
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: pdimov at gmail dot com
Target Milestone: ---
The following program
#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
struct X
{
float f;
};
int main()
{
constexpr X x{ 3.14f };
STATIC_ASSERT( x.f == 3.14f );
}
fails under GCC 13/14 with
<source>: In function 'int main()':
<source>:11:24: error: static assertion failed: x.f == 3.14f
11 | STATIC_ASSERT( x.f == 3.14f );
| ~~~~^~~~~~~~
<source>:1:42: note: in definition of macro 'STATIC_ASSERT'
1 | #define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
| ^~~~~~~~~~~
<source>:11:24: note: the comparison reduces to '(3.14000010490417480469e+0l ==
3.1400000000000000001e+0l)'
11 | STATIC_ASSERT( x.f == 3.14f );
| ~~~~^~~~~~~~
when compiled with -m32 -std=c++XX under x86 (https://godbolt.org/z/Ghs7j5Teq).
The reason is that -std=c++XX implies -fexcess-precision=standard
(https://godbolt.org/z/zx4rn4j5W).
Previous versions worked fine.
