From: Segher Boessenkool <segher@kernel.crashing.org>
To: Edward Diener <eldlistmailingz@tropicsoft.com>
Cc: gcc-help@gcc.gnu.org
Subject: Re: Possible __VA_OPT__ bug
Date: Thu, 31 Oct 2019 17:15:00 -0000 [thread overview]
Message-ID: <20191031171458.GU28442@gate.crashing.org> (raw)
In-Reply-To: <qpf2uf$7gpc$1@blaine.gmane.org>
Hi Edward,
On Thu, Oct 31, 2019 at 12:42:54PM -0400, Edward Diener wrote:
> Given:
>
> #define NO_DATA
> #define TRY_VA_OPT(...) __VA_OPT__ (0) 1
>
> TRY_VA_OPT() -> expands to 1 as expected
> TRY_VA_OPT(NO_DATA) -> expands to 0 1 which is not expected
>
> when compiled with gcc-9.2 with -std=c++2a.
Why is that not expected? The variadic macro TRY_VA_OPT does get tokens
in its variable argument (namely, NO_DATA), so __VA_OPT__ expands to its
argument (which is 0).
https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html
Segher
next prev parent reply other threads:[~2019-10-31 17:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-31 16:43 Edward Diener
2019-10-31 17:15 ` Segher Boessenkool [this message]
2019-10-31 18:50 ` Edward Diener
2019-10-31 20:21 ` Segher Boessenkool
2019-10-31 20:28 ` Edward Diener
2019-10-31 21:28 ` Jędrzej Dudkiewicz
2019-10-31 21:31 ` Jędrzej Dudkiewicz
2019-11-01 14:39 ` Edward Diener
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