[Bug c++/106485] New: Can't use heap pointer in `static_assert`

[Bug c++/106485] New: Can't use heap pointer in `static_assert`

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485

            Bug ID: 106485
           Summary: Can't use heap pointer in `static_assert`
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://godbolt.org/z/W4r6oMa3M.

```C++
struct I {
  int* i = new int{1};
  constexpr ~I() { delete i; }
};
static_assert([] { return I{}.i; }());
static_assert(I{}.i);
```

```
<source>:5:19: error: non-constant condition for static assertion
    5 | static_assert(I{}.i);
      |               ~~~~^
<source>:5:19: error: the value of '<anonymous>' is not usable in a constant
expression
<source>:5:17: note: '<anonymous>' was not declared 'constexpr'
    5 | static_assert(I{}.i);
      |                 ^
Compiler returned: 1
```

It works wrapped in an IILE, or if the `int` is uninitialized.

[Bug c++/106485] Can't use heap pointer in `static_assert`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=105826

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think this is a dup of bug 105826.

[Bug c++/106485] Can't use heap pointer in `static_assert`

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485

--- Comment #2 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
I think that's different. Actually, I think it's Clang that's wrong. As
mentioned at
https://cpplang.slack.com/archives/C21PKDHSL/p1656857369259539?thread_ts=1656856509.892079&cid=C21PKDHSL:
> The expression of the `static_assert` is not an
> [immediate function context](https://eel.is/c++draft/expr.const#def:immediate_function_context).
> Wrapping it in `[]() consteval { return s().empty(); }()` [works](https://godbolt.org/z/PKTE7zofW),
> whereas removing that `consteval` causes Clang to also complain.

See https://godbolt.org/z/4GMxo13vv.
```C++
#include <string>
consteval auto s() { return std::string(); }
static_assert(s().empty()); // Only Clang accepts.
// static_assert([]() consteval { return s().empty(); }()); // All accept.
// static_assert([]() { return s().empty(); }()); // All reject.
```

Opened https://github.com/llvm/llvm-project/issues/57627 for that.

[Bug c++/106485] Can't use heap pointer in `static_assert`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-01-19

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think comment #0 is a different issue from comment #2 really.
comment #0 has a temporary while comment #2 has an consteval.

Also GCC accepts this just fine though:
#include <string>
static_assert(!std::string{"abcdegfgggggggggggg"}.empty());

[Bug c++/106485] Can't use heap pointer in `static_assert`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Oh wait there comment #0 is still invalid (undefined?) code:
```
struct I {
  int* i = new int{1};
  constexpr ~I() { delete i; }
};
static_assert([] ()consteval { return I{}.i != 0; }());
```
Works just fine.

So yes this again is the same issue of static_assert not being immediate
function context.