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From: "jlame646 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107065] GCC treats rvalue as an lvalue
Date: Wed, 28 Sep 2022 12:09:13 +0000 [thread overview]
Message-ID: <bug-107065-4-QVI7BDoQ00@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-107065-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107065
--- Comment #3 from Jason Liam <jlame646 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #1)
> Reduced to remove the library dependency:
>
> enum Cat { prvalue, lvalue, xvalue };
>
> template<typename T>
> struct value_category {
> // Or can be an integral or enum value
> static constexpr auto value = prvalue;
> };
>
> template<typename T>
> struct value_category<T&> {
> static constexpr auto value = lvalue;
> };
>
> template<typename T>
> struct value_category<T&&> {
> static constexpr auto value = xvalue;
> };
>
> // Double parens for ensuring we inspect an expression,
> // not an entity
> #define VALUE_CATEGORY(expr) value_category<decltype((expr))>::value
>
> constexpr bool global = true;
> static_assert( VALUE_CATEGORY(!(!global)) == prvalue, "GCC gets this right"
> );
>
> int main()
> {
> bool b = true;
> if ( VALUE_CATEGORY(!(!b)) != prvalue )
> throw 1;
> }
Here is another reduced demo: https://godbolt.org/z/hGhfrKrad
```
#include <iostream>
int main() {
bool b = true;
std::cout << std::is_same<decltype(!(!b)), bool>::value << "\n";
auto bb = (!(!b));
std::cout << std::is_same<decltype(bb), bool>::value << "\n";
}
```
next prev parent reply other threads:[~2022-09-28 12:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 7:35 [Bug c++/107065] New: GCC treats rvalue like lvalue jlame646 at gmail dot com
2022-09-28 12:00 ` [Bug c++/107065] GCC treats rvalue as an lvalue redi at gcc dot gnu.org
2022-09-28 12:06 ` jlame646 at gmail dot com
2022-09-28 12:09 ` jlame646 at gmail dot com [this message]
2022-09-28 12:50 ` redi at gcc dot gnu.org
2022-09-28 13:41 ` mpolacek at gcc dot gnu.org
2022-09-28 14:32 ` jlame646 at gmail dot com
2022-09-28 15:34 ` mpolacek at gcc dot gnu.org
2022-09-29 18:24 ` glisse at gcc dot gnu.org
2022-09-29 19:01 ` jakub at gcc dot gnu.org
2022-09-30 7:12 ` jakub at gcc dot gnu.org
2022-09-30 7:13 ` jakub at gcc dot gnu.org
2022-09-30 8:03 ` glisse at gcc dot gnu.org
2022-09-30 8:27 ` jakub at gcc dot gnu.org
2022-09-30 8:47 ` glisse at gcc dot gnu.org
2022-12-15 18:18 ` cvs-commit at gcc dot gnu.org
2022-12-16 9:23 ` jakub at gcc dot gnu.org
2023-02-10 17:44 ` cvs-commit at gcc dot gnu.org
2023-05-02 20:12 ` cvs-commit at gcc dot gnu.org
2023-05-03 15:19 ` cvs-commit at gcc dot gnu.org
2023-05-04 7:20 ` jakub at gcc dot gnu.org
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