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* [Bug c++/98859] New: pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive
@ 2021-01-27 20:52 richard-gccbugzilla at metafoo dot co.uk
2021-01-27 20:54 ` [Bug c++/98859] " mpolacek at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: richard-gccbugzilla at metafoo dot co.uk @ 2021-01-27 20:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98859
Bug ID: 98859
Summary: pedantic error on use of __VA_OPT__ before C++20 is
unnecessary and counterproductive
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: richard-gccbugzilla at metafoo dot co.uk
Target Milestone: ---
There's no good way in ISO C or C++ to express what the GNU ,##__VA_ARGS__
extension does prior to the addition of __VA_OPT__. However, code targeting new
compilers (that doesn't want to use GNU C / GNU C++) cannot reliably use
__VA_OPT__ instead of the comma paste extension, because GCC's -pedantic-errors
mode rejects it outside C++20.
Such rejection is unnecessary: __VA_OPT__ is a reserved identifier in other
language modes, so there is no conformance reason to issue a diagnostic on its
use. I think it'd be useful for GCC to unconditionally allow using __VA_OPT__
in all language modes. (I'm changing Clang to do the same.)
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug c++/98859] pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive 2021-01-27 20:52 [Bug c++/98859] New: pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive richard-gccbugzilla at metafoo dot co.uk @ 2021-01-27 20:54 ` mpolacek at gcc dot gnu.org 2021-07-30 15:49 ` wuyongwei at gmail dot com 2022-11-19 11:58 ` wjwray at gmail dot com 2 siblings, 0 replies; 4+ messages in thread From: mpolacek at gcc dot gnu.org @ 2021-01-27 20:54 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98859 Marek Polacek <mpolacek at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |mpolacek at gcc dot gnu.org Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed| |2021-01-27 Keywords| |diagnostic --- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> --- That sounds reasonable. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/98859] pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive 2021-01-27 20:52 [Bug c++/98859] New: pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive richard-gccbugzilla at metafoo dot co.uk 2021-01-27 20:54 ` [Bug c++/98859] " mpolacek at gcc dot gnu.org @ 2021-07-30 15:49 ` wuyongwei at gmail dot com 2022-11-19 11:58 ` wjwray at gmail dot com 2 siblings, 0 replies; 4+ messages in thread From: wuyongwei at gmail dot com @ 2021-07-30 15:49 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98859 Yongwei Wu <wuyongwei at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |wuyongwei at gmail dot com --- Comment #2 from Yongwei Wu <wuyongwei at gmail dot com> --- Here is anotehr good reason: https://stackoverflow.com/questions/48045470/portably-detect-va-opt-support/48045656 People can detect the presence of __VA_OPT__ support. Currently, the detection code would cause warnings when -std is set to something like "c++17" (though luckily not "gnu++17"). ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/98859] pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive 2021-01-27 20:52 [Bug c++/98859] New: pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive richard-gccbugzilla at metafoo dot co.uk 2021-01-27 20:54 ` [Bug c++/98859] " mpolacek at gcc dot gnu.org 2021-07-30 15:49 ` wuyongwei at gmail dot com @ 2022-11-19 11:58 ` wjwray at gmail dot com 2 siblings, 0 replies; 4+ messages in thread From: wjwray at gmail dot com @ 2022-11-19 11:58 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98859 Will Wray <wjwray at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |wjwray at gmail dot com --- Comment #3 from Will Wray <wjwray at gmail dot com> --- Linking the related MSVC issue /Zc:preprocessor __VA_OPT__ is not enabled with /std:c++17 https://developercommunity.visualstudio.com/t/Zc:preprocessor-__VA_OPT__-is-not-enabl ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-11-19 11:58 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-01-27 20:52 [Bug c++/98859] New: pedantic error on use of __VA_OPT__ before C++20 is unnecessary and counterproductive richard-gccbugzilla at metafoo dot co.uk 2021-01-27 20:54 ` [Bug c++/98859] " mpolacek at gcc dot gnu.org 2021-07-30 15:49 ` wuyongwei at gmail dot com 2022-11-19 11:58 ` wjwray at gmail dot com
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