https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120204
Bug ID: 120204
Summary: `is not usable as a 'constexpr' function because` and
no reason why
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
```
template<class T, int t>
struct array{};
template <typename... TArgs> struct ILEArglist {
using Sizes = array<int, sizeof...(TArgs)>;
static constexpr auto size() {
Sizes &offsets_c = offsets;
return 0;
}
array<char, size()> offsets();
};
auto arglist = ILEArglist<>();
```
GCC gives:
```
<source>: In instantiation of 'struct ILEArglist<>':
<source>:13:29: required from here
13 | auto arglist = ILEArglist<>();
| ^
<source>:11:19: error: 'static constexpr auto ILEArglist<TArgs>::size() [with
TArgs = {}]' called in a constant expression
11 | array<char, size()> offsets();
| ~~~~^~
<source>:7:25: note: 'static constexpr auto ILEArglist<TArgs>::size() [with
TArgs = {}]' is not usable as a 'constexpr' function because:
7 | static constexpr auto size() {
| ^~~~
<source>:11:19: note: in template argument for type 'int'
11 | array<char, size()> offsets();
| ~~~~^~
Compiler returned: 1
```
While clang gives:
```
<source>:8:24: error: call to non-static member function without an object
argument
8 | Sizes &offsets_c = offsets;
| ^~~~~~~
<source>:8:12: error: declaration of reference variable 'offsets_c' requires an
initializer
8 | Sizes &offsets_c = offsets;
| ^~~~~~~~~
<source>:11:15: note: in instantiation of member function 'ILEArglist<>::size'
requested here
11 | array<char, size()> offsets();
| ^
<source>:13:16: note: in instantiation of template class 'ILEArglist<>'
requested here
13 | auto arglist = ILEArglist<>();
| ^
```
