From: Chris Peterson <cpeterso@cpeterso.com>
To: gcc-help@gcc.gnu.org
Subject: Re: Bug in GCC's resolution of C++20 reversed operator== functions?
Date: Mon, 1 Apr 2024 10:35:28 -0700 [thread overview]
Message-ID: <CAL+j+jjJB+LFFpufQ0tNbjxNhXrx5tbsVpb5YDLhD+fh2kg--w@mail.gmail.com> (raw)
In-Reply-To: <CAL+j+jiXNhTYvVg4tYSsxvcQhQmzp4=0qrr-w_sS=GUPrUw+gg@mail.gmail.com>
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I filed a bug in Bugzilla:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114549
On Sun, Mar 31, 2024 at 3:00 PM Chris Peterson <cpeterso@cpeterso.com>
wrote:
> 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
>
prev parent reply other threads:[~2024-04-01 17:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-31 22:00 Chris Peterson
2024-04-01 8:59 ` Jonathan Wakely
2024-04-01 17:35 ` Chris Peterson [this message]
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