[Bug c++/120785] No compiler warning when wrapping a packed C-style array in a std::span, array memcpy instead

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120785

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2025-06-23
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
           Keywords|                            |diagnostic
             Blocks|                            |87403

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced testcase:
```
struct MyStruct {
    int values[1];
} __attribute__((packed));

template <int N>
void f(const int (&a)[N]);

int main() {
    MyStruct *a = new MyStruct();
    f(a->values);
}
```

So span is normally not warning about temporaries but I suspect we should warn
for the above case even without not dealing with span which creates a temporary
because of the non-binding to const int for the packed fields.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87403
[Bug 87403] [Meta-bug] Issues that suggest a new warning