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From: "aaron at aaronballman dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107980] va_start incorrectly accepts an arbitrary number of arguments in C2x
Date: Mon, 05 Dec 2022 21:04:31 +0000 [thread overview]
Message-ID: <bug-107980-4-dI1XcXTSDW@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-107980-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107980
--- Comment #2 from Aaron Ballman <aaron at aaronballman dot com> ---
(In reply to Andrew Pinski from comment #1)
> Hmm from https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3054.pdf :
> ```
> 7.16.1.4 The va_start macro
> void va_start(va_list ap, ...);
>
>
> Any additional arguments are not used by
> the macro and will not be expanded or evaluated for any reason.
> ```
>
>
> I would assume since it is `arguments` rather than additional argument, that
> it could be more than one additional argument.
Yes, the standard says "arguments" because there can be additional arguments
due to using `...`. However, think about the user experience:
```
// This should always be happily accepted because it's
// idiomatic C before C2x and it's valid C in C2x and later.
va_start(list, some_arg);
// This should be accepted in C2x mode and if you care
// to do such things, warn the user that it's incompatible
// with standards before C2x. Pre-C2x, this is an error.
va_start(list);
// Under what circumstances is this anything other than
// programmer confusion? It's invalid before C2x and the
// extra args are meaningless in C2x and later.
va_start(list, 1, 2, 3, 4);
```
next prev parent reply other threads:[~2022-12-05 21:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 20:46 [Bug c/107980] New: " aaron at aaronballman dot com
2022-12-05 20:57 ` [Bug c/107980] " pinskia at gcc dot gnu.org
2022-12-05 21:04 ` aaron at aaronballman dot com [this message]
2022-12-05 21:10 ` [Bug c/107980] va_start does not warn about an arbitrary number of arguments in C2x mode pinskia at gcc dot gnu.org
2022-12-05 21:17 ` pinskia at gcc dot gnu.org
2022-12-06 13:37 ` aaron at aaronballman dot com
2022-12-06 13:44 ` pinskia at gcc dot gnu.org
2022-12-06 13:51 ` jakub at gcc dot gnu.org
2022-12-06 14:04 ` aaron at aaronballman dot com
2022-12-06 15:42 ` aaron at aaronballman dot com
2022-12-06 15:46 ` jakub at gcc dot gnu.org
2022-12-06 16:13 ` aaron at aaronballman dot com
2022-12-07 0:55 ` joseph at codesourcery dot com
2022-12-07 14:57 ` jakub at gcc dot gnu.org
2022-12-07 15:00 ` aaron at aaronballman dot com
2022-12-07 15:38 ` pinskia at gcc dot gnu.org
2022-12-07 16:42 ` aaron at aaronballman dot com
2022-12-07 18:29 ` joseph at codesourcery dot com
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