From: Chris Peterson <cpeterso@cpeterso.com>
To: gcc-help@gcc.gnu.org
Subject: Bug in GCC's resolution of C++20 reversed operator== functions?
Date: Sun, 31 Mar 2024 15:00:49 -0700 [thread overview]
Message-ID: <CAL+j+jiXNhTYvVg4tYSsxvcQhQmzp4=0qrr-w_sS=GUPrUw+gg@mail.gmail.com> (raw)
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While updating Firefox from -std=c++17 to -std=c++20, I found a case where
GCC's resolution of C++20 reversed operator== functions behaves differently
from the Clang, MSVC, and ICX compilers. I believe this difference was a
regression in GCC 10.1.
Here's a Godbolt test case comparing those compilers' output:
https://godbolt.org/z/qneax5oaW
```
#include <type_traits>
struct Thing {
template <typename T>
bool operator==(const T& rhs) const {
/* This operator== is selected by:
* GCC versions >= 10.1 -std=c++17
* GCC version 9.5 -std=c++2a
* Clang 18.1 -std=c++2a
* MSVC 19.38 -std=c++20
* Intel's ICX 2024.0.0 -std=c++20
*/
return false;
}
};
template <typename T>
bool operator==(T const& lhs, Thing const& rhs) {
/* This operator== is selected by:
* GCC versions >= 10.1 -std=c++2a
*/
return true;
}
bool test() {
Thing const v{};
return v == 3;
}
```
(I have an account on the GCC Bugzilla, but I'm not able to log in or reset
my password to file a bug there.)
chris
next reply other threads:[~2024-03-31 22:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-31 22:00 Chris Peterson [this message]
2024-04-01 8:59 ` Jonathan Wakely
2024-04-01 17:35 ` Chris Peterson
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