https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123889
Bug ID: 123889
Summary: C++11 diagnostic about non-constexpr functions is
useless
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: nikolasklauser at berlin dot de
Target Milestone: ---
```
template <class T>
constexpr int func(T) {
return 1;
return 2;
}
static_assert(func(1) == 1);
```
generates the following error:
<source>:9:23: error: non-constant condition for static assertion
9 | static_assert(func(1) == 1);
| ~~~~~~~~^~~~
<source>:9:19: error: 'constexpr int func(T) [with T = int]' called in a
constant expression
9 | static_assert(func(1) == 1);
| ~~~~^~~
<source>:4:15: note: 'constexpr int func(T) [with T = int]' is not usable as a
'constexpr' function because:
4 | constexpr int func(T) {
| ^~~~
This error is 100% useless, as it doesn't tell me at all what's wrong.
On a side note, it would be nice if GCC didn't error on more than a single
return statement in C++11 mode, since Clang allows more complex expressions as
an extension already (and also happens to issue a usable warning in this
example).
It looks like the diagnostic was better in GCC 11.
