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* [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected @ 2023-06-20 15:14 serge.ayoun at outlook dot com 2023-06-20 15:18 ` [Bug c++/110321] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: serge.ayoun at outlook dot com @ 2023-06-20 15:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110321 Bug ID: 110321 Summary: Double precision comaprison does not seem to work well when -std=c++17 option is selected Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: serge.ayoun at outlook dot com Target Milestone: --- The following code: int main(int, char**) { double a = 2.2; if ( a == 2.2) return 1; return 0; } compiled and link with the following instruction: g++ -O0 -m32 -std=c++17 with gcc 11.1, returns 1 as expected with gcc 13.1, returns 0. when -std=c++17 is removed, both return 0 as expected. for exact reproduction See: https://godbolt.org/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAMzwBtMA7AQwFtMQByARg9KtQYEAysib0QXACx8BBAKoBnTAAUAHpwAMvAFYTStJg1DIApACYAQuYukl9ZATwDKjdAGFUtAK4sGe1wAyeAyYAHI%2BAEaYxHoADqgKhE4MHt6%2BcQlJAkEh4SxRMVy2mPaOAkIETMQEqT5%2BRXaYDskVVQQ5YZHRegqV1bXpDX3twZ353VwAlLaoXsTI7BzBBADULEzBEMukK8gIVQBUB5MmGgCCJgDsFiunZysPK%2BizEfQrTLcAzAAiK2YAdGYTJ8rOdHis8FQVhB3l9vsDfgCzJMVsRMAQ5gwVlxgTc7uC0RjiFiNLjbucrt8ONNaJwAKy8PwcLSkVCcNzWawrBSzeaYW5mT48UgETTU6YAaxAkku/zpAE4uBoAGzyz6fDRceXyy7Kun6TiSRli1mcXgKEAaEVi6ZwWAwRAoVAsWJ0aLkShoF1umLALhC0hYABueAWADU8JgAO4AeVijE4wpotAI0QtEAiJoiwSqAE9E7xs8xiLmYxFtE1RdxeF62IIYwxaPnmbwsBEvMA3GJaBbq4HMOsjOIW4G8GjmkHML2WZhVE0vKmC%2BRBCUTbQ8BFiHmPFgTQRiHgWAXplQDMAFBHo3GE33%2BIIRGJ2FIZIJFCp1CPdEUDEYUJzLPoG4WpA0yoLEZQML2AC0MYaCsUEsJ8Zjwb06AIqYljWFwly8Kgk7EAeWDARA0yNM0zgQK4Az1KQgSjHkBQZIkEHUUxWQMB0DETMUpQtMMrENCUlZ8W0nFdIUtj8Z4dQ9MMYnjIUpG8gsEg0vSxojmyHArKoAAcypQcqkgrMAyDINinz/Fw0K4IQJACkKky8FWWiTJKIB0latIcEapBHpI8r/Boum6ZcZjypqyqXPpdKXKQTIslp5qWtaLa2g6EBIF6rr0GQFAQNlPogH6XBFMGoaYJesbxkySZ0KmxDppmI5FnmS6tSWZYVg4S61owBANk2Jpth2Xa0D2S5YIOwDDiy%2BDjo4k7Trws7zoufbLKuI7rpu24YIsLL7oex58GeF6RtVN5JrID7iM%2Bd7yEoagmroZj6IYxj/jYO3EaB4HJNBsHwYhyFQah6FfdhuH4YRU7wKRQnkX4lEMO40mDLRqPyYxRTxMxyQCaQePsdj3FkRBrT9OjNHkyJ1SkxJvRtITTP0/R4mqTMcwqVMBocAy8UmlpOn6YZxmmeZpVWTZ%2BBEMQDlTM5NrTAgmBMFgMQkXzvlHp5/yKlwZiXBo8q6Uh/qSJ8guaWatgpS54qkFKdIApIwVqiqqq6RoGiCvq3mfBpiW2w7bl82YQe4SHyukPhiTOJIQA%3D Thanks, Serge ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/110321] Double precision comaprison does not seem to work well when -std=c++17 option is selected 2023-06-20 15:14 [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected serge.ayoun at outlook dot com @ 2023-06-20 15:18 ` redi at gcc dot gnu.org 2023-06-20 15:21 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2023-06-20 15:18 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110321 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- As described in the manual, sincve GCC 13.1 -fexcess-precision=standard is enabled by -std=c++NN (but not by -std=gnu++NN). This means the literal 2.2 is represented with excess precision, and so is not equal to the same value converted to double. You can use (a == (double)2.2) to make the comparison work. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/110321] Double precision comaprison does not seem to work well when -std=c++17 option is selected 2023-06-20 15:14 [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected serge.ayoun at outlook dot com 2023-06-20 15:18 ` [Bug c++/110321] " redi at gcc dot gnu.org @ 2023-06-20 15:21 ` pinskia at gcc dot gnu.org 2023-06-20 15:31 ` redi at gcc dot gnu.org 2023-06-20 16:21 ` serge.ayoun at outlook dot com 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-06-20 15:21 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110321 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |INVALID Status|UNCONFIRMED |RESOLVED --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Invalid as explained. More over this is basically bug 323 in reverse. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/110321] Double precision comaprison does not seem to work well when -std=c++17 option is selected 2023-06-20 15:14 [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected serge.ayoun at outlook dot com 2023-06-20 15:18 ` [Bug c++/110321] " redi at gcc dot gnu.org 2023-06-20 15:21 ` pinskia at gcc dot gnu.org @ 2023-06-20 15:31 ` redi at gcc dot gnu.org 2023-06-20 16:21 ` serge.ayoun at outlook dot com 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2023-06-20 15:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110321 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|INVALID |FIXED --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #1) > You can use (a == (double)2.2) to make the comparison work. Or use -std=gnu++17, or use -std=c++17 -fexcess-precision=fast ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/110321] Double precision comaprison does not seem to work well when -std=c++17 option is selected 2023-06-20 15:14 [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected serge.ayoun at outlook dot com ` (2 preceding siblings ...) 2023-06-20 15:31 ` redi at gcc dot gnu.org @ 2023-06-20 16:21 ` serge.ayoun at outlook dot com 3 siblings, 0 replies; 5+ messages in thread From: serge.ayoun at outlook dot com @ 2023-06-20 16:21 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110321 --- Comment #4 from Serge Ayoun <serge.ayoun at outlook dot com> --- Thanks guys for your help ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-06-20 16:21 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-06-20 15:14 [Bug c++/110321] New: Double precision comaprison does not seem to work well when -std=c++17 option is selected serge.ayoun at outlook dot com 2023-06-20 15:18 ` [Bug c++/110321] " redi at gcc dot gnu.org 2023-06-20 15:21 ` pinskia at gcc dot gnu.org 2023-06-20 15:31 ` redi at gcc dot gnu.org 2023-06-20 16:21 ` serge.ayoun at outlook dot com
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