[Bug c++/96575] New: std::ranges::sort is not usable as a 'constexpr' function when saving its return value in lambda function
hewillk at gmail dot com
gcc-bugzilla@gcc.gnu.org
Wed Aug 12 01:23:58 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96575
Bug ID: 96575
Summary: std::ranges::sort is not usable as a 'constexpr'
function when saving its return value in lambda
function
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: hewillk at gmail dot com
Target Milestone: ---
(https://godbolt.org/z/W8zx58)
#include <array>
#include <algorithm>
constexpr auto f(auto algo) {
return [=] {
// this one is okay
// algo(std::array{1, 0});
// this one is also okay
// auto it = algo(std::array{0, 1});
auto it = algo(std::array{1, 0});
return 0;
}();
}
int main()
{
static_assert(f(std::ranges::sort) == 0);
}
This fails on gcc 10.2 and trunk with:
<source>:13:23: error: 'constexpr auto f(auto:16) [with auto:16 =
std::ranges::__sort_fn]' called in a constant expression
13 | constexpr auto i = f(std::ranges::sort);
| ~^~~~~~~~~~~~~~~~~~~
<source>:4:16: note: 'constexpr auto f(auto:16) [with auto:16 =
std::ranges::__sort_fn]' is not usable as a 'constexpr' function because:
4 | constexpr auto f(auto algo) {
| ^
<source>:8:8: error: call to non-'constexpr' function
'f<std::ranges::__sort_fn>::<lambda()>'
5 | return [=] {
| ~~~~~
6 | auto it = algo(std::array{1, 0});
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7 | return 0;
| ~~~~~~~~~
8 | }();
| ~^~
<source>:5:14: note: 'f<std::ranges::__sort_fn>::<lambda()>' is not usable as a
'constexpr' function because:
5 | return [=] {
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