https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96862
Bug ID: 96862
Summary: -frounding-math -std=c++2a error: '(1.29e+2 *
6.9314718055994529e-1)' is not a constant expression
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: Laurent.Rineau__gcc at normalesup dot org
Target Milestone: ---
Commit e6c76f0d3327bf00c96f5a63961c1d5ab77512db introduced a compilation error
with `-frounding-math -std=c++2a`: it seems that, with `-frounding-math` a
floating-point expression cannot be constexpr.
# cat test.cpp
#include <string>
# g++ --version
g++ (GCC) 11.0.0 20200828 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# g++ -std=c++2a -frounding-math test.cpp
In file included from /usr/local/include/c++/11.0.0/bits/range_access.h:40,
from /usr/local/include/c++/11.0.0/string:54,
from test.cpp:1:
/usr/local/include/c++/11.0.0/bits/max_size_type.h:708:35: error: '(1.29e+2 *
6.9314718055994529e-1)' is not a constant expression
708 | = static_cast<int>(digits * numbers::ln2 / numbers::ln10);
| ~~~~~~~^~~~~~~~~~~~~~
/usr/local/include/c++/11.0.0/bits/max_size_type.h:734:50: error:
'(8.8722839111672997e+1 / 2.3025850929940459e+0)' is not a constant expression
734 | = static_cast<int>(digits * numbers::ln2 / numbers::ln10);
| ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
