https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115902
Bug ID: 115902
Summary: Can't call immediate function within "if consteval"
when optimizing
Product: gcc
Version: 14.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at nospam dot scs.stanford.edu
Target Milestone: ---
When optimizing, g++ seems to try calling immediate functions inside "if
consteval" and then reject what should be valid code. Here is a simple example
(which I place in the public domain):
```
// g++ -std=c++23 -c -O2 consteval.cc
consteval int
plusone(int n)
{
return n + 1;
}
constexpr int
maybeplusone(int n)
{
if consteval {
return plusone(n);
}
else {
return n;
}
}
int
not_consteval()
{
return maybeplusone(1);
}
```
It gives the following error:
```
$ g++ -std=c++23 -c -O2 consteval.cc
consteval.cc: In function 'int not_consteval()':
consteval.cc:23:22: in 'constexpr' expansion of 'maybeplusone(1)'
consteval.cc:13:19: error: call to consteval function 'plusone(n)' is not a
constant expression
13 | return plusone(n);
| ~~~~~~~^~~
consteval.cc:13:20: error: 'n' is not a constant expression
13 | return plusone(n);
| ^
$
```
The code compiles fine without optimization, and also works with clang 18.
