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From: "StevenSun2021 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/108218] [12 Regression] Constant arguments in the new
 expression is not checked in unevaluated operand
Date: Sat, 24 Dec 2022 16:00:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108218

--- Comment #1 from Steven Sun <StevenSun2021 at hotmail dot com> ---
My concern is that, expressions within the require expressions are also
considered as "unevaluated operands".

Thus, the following concept is evaluated as true, but the program is ill-fo=
rmed
and does not compile (since gcc 12)


https://godbolt.org/z/bcc398chG
```
template<class T>
concept C =3D requires
{
    new int[(int)sizeof(T) - 4];
};

template<typename T> requires C<T>
class CC {
    CC() {
        new int[(int)sizeof(T) - 4];
    }
};

template class CC<char>;

```



<source>: In instantiation of 'CC<T>::CC() [with T =3D char]':
<source>:16:16:   required from here
<source>:12:32: error: size '-3' of array is negative
   12 |         new int[(int)sizeof(T) - 4];
      |                 ~~~~~~~~~~~~~~~^~~=