https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111056
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We don't warn for the same reason as we don't warn for `constexpr` because the
value is known at compile time.
That is:
```
#include <stdio.h>
int main()
{
signed int a = 1;
enum : signed int { b = 1 }d = b;
constexpr int t = 1;
unsigned int c = -1;
if (a < c) // condition is true, -Wsign-compare warns about it
puts("a < c");
if (t < c) // condition is true, but no warning
puts("t < c");
if (b < c) // condition is true, but no warning
puts("b < c");
if (d < c) // condition is true, -Wsign-compare warns about it
puts("d < c");
return 0;
}
```
`t` and `b` here are replaced with 1. But with a variable that is declared as
the enum type we do warn.
I think this is correct behavior really.
clang has the same behavior (well they don't yet support constexpr though).
