* [Bug c/114780] Using C23 nullptr as sentinel gives missing sentinel warning
2024-04-19 9:58 [Bug c/114780] New: Using C23 nullptr as sentinel gives missing sentinel warning cazfi74 at gmail dot com
@ 2024-04-19 11:10 ` jakub at gcc dot gnu.org
2024-04-19 22:13 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-04-19 11:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Ever confirmed|0 |1
CC| |jakub at gcc dot gnu.org
Last reconfirmed| |2024-04-19
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 57989
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57989&action=edit
gcc14-pr114780.patch
Untested fix.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug c/114780] Using C23 nullptr as sentinel gives missing sentinel warning
2024-04-19 9:58 [Bug c/114780] New: Using C23 nullptr as sentinel gives missing sentinel warning cazfi74 at gmail dot com
2024-04-19 11:10 ` [Bug c/114780] " jakub at gcc dot gnu.org
@ 2024-04-19 22:13 ` cvs-commit at gcc dot gnu.org
2024-04-19 22:25 ` jakub at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-04-19 22:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780
--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:2afdecccbaf5c5b1c7a235509b37092540906c02
commit r14-10046-g2afdecccbaf5c5b1c7a235509b37092540906c02
Author: Jakub Jelinek <jakub@redhat.com>
Date: Sat Apr 20 00:12:36 2024 +0200
c-family: Allow arguments with NULLPTR_TYPE as sentinels [PR114780]
While in C++ the ellipsis argument conversions include
"An argument that has type cv std::nullptr_t is converted to type void*"
in C23 a nullptr_t argument is not promoted in any way, but va_arg
description says:
"the type of the next argument is nullptr_t and type is a pointer type that
has the same
representation and alignment requirements as a pointer to a character
type."
So, while in C++ check_function_sentinel will never see NULLPTR_TYPE, for
C23 it can see that and currently we incorrectly warn about those.
The only question is whether we should warn on any argument with
nullptr_t type or just about nullptr (nullptr_t argument with integer_zerop
value). Through undefined behavior guess one could pass non-NULL pointer
that way, say by union { void *p; nullptr_t q; } u; u.p = &whatever;
and pass u.q to ..., but valid code should always pass something that will
read as (char *) 0 when read using va_arg (ap, char *), so I think it is
better not to warn rather than warn in those cases.
Note, clang seems to pass (void *)0 rather than expression of nullptr_t
type to ellipsis in C23 mode as if it did the C++ ellipsis argument
conversions, in that case guess not warning about that would be even safer,
but what GCC does I think follows the spec more closely, even when in a
valid program one shouldn't be able to observe the difference.
2024-04-20 Jakub Jelinek <jakub@redhat.com>
PR c/114780
* c-common.cc (check_function_sentinel): Allow as sentinel any
argument of NULLPTR_TYPE.
* gcc.dg/format/sentinel-2.c: New test.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug c/114780] Using C23 nullptr as sentinel gives missing sentinel warning
2024-04-19 9:58 [Bug c/114780] New: Using C23 nullptr as sentinel gives missing sentinel warning cazfi74 at gmail dot com
2024-04-19 11:10 ` [Bug c/114780] " jakub at gcc dot gnu.org
2024-04-19 22:13 ` cvs-commit at gcc dot gnu.org
@ 2024-04-19 22:25 ` jakub at gcc dot gnu.org
2024-04-21 4:09 ` cvs-commit at gcc dot gnu.org
2024-04-23 6:42 ` jakub at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-04-19 22:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 14.1 so far.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/114780] Using C23 nullptr as sentinel gives missing sentinel warning
2024-04-19 9:58 [Bug c/114780] New: Using C23 nullptr as sentinel gives missing sentinel warning cazfi74 at gmail dot com
` (2 preceding siblings ...)
2024-04-19 22:25 ` jakub at gcc dot gnu.org
@ 2024-04-21 4:09 ` cvs-commit at gcc dot gnu.org
2024-04-23 6:42 ` jakub at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-04-21 4:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:e802786436851b1f5efca21a14d4f41c83c83f4f
commit r13-8637-ge802786436851b1f5efca21a14d4f41c83c83f4f
Author: Jakub Jelinek <jakub@redhat.com>
Date: Sat Apr 20 00:12:36 2024 +0200
c-family: Allow arguments with NULLPTR_TYPE as sentinels [PR114780]
While in C++ the ellipsis argument conversions include
"An argument that has type cv std::nullptr_t is converted to type void*"
in C23 a nullptr_t argument is not promoted in any way, but va_arg
description says:
"the type of the next argument is nullptr_t and type is a pointer type that
has the same
representation and alignment requirements as a pointer to a character
type."
So, while in C++ check_function_sentinel will never see NULLPTR_TYPE, for
C23 it can see that and currently we incorrectly warn about those.
The only question is whether we should warn on any argument with
nullptr_t type or just about nullptr (nullptr_t argument with integer_zerop
value). Through undefined behavior guess one could pass non-NULL pointer
that way, say by union { void *p; nullptr_t q; } u; u.p = &whatever;
and pass u.q to ..., but valid code should always pass something that will
read as (char *) 0 when read using va_arg (ap, char *), so I think it is
better not to warn rather than warn in those cases.
Note, clang seems to pass (void *)0 rather than expression of nullptr_t
type to ellipsis in C23 mode as if it did the C++ ellipsis argument
conversions, in that case guess not warning about that would be even safer,
but what GCC does I think follows the spec more closely, even when in a
valid program one shouldn't be able to observe the difference.
2024-04-20 Jakub Jelinek <jakub@redhat.com>
PR c/114780
* c-common.cc (check_function_sentinel): Allow as sentinel any
argument of NULLPTR_TYPE.
* gcc.dg/format/sentinel-2.c: New test.
(cherry picked from commit 2afdecccbaf5c5b1c7a235509b37092540906c02)
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug c/114780] Using C23 nullptr as sentinel gives missing sentinel warning
2024-04-19 9:58 [Bug c/114780] New: Using C23 nullptr as sentinel gives missing sentinel warning cazfi74 at gmail dot com
` (3 preceding siblings ...)
2024-04-21 4:09 ` cvs-commit at gcc dot gnu.org
@ 2024-04-23 6:42 ` jakub at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-04-23 6:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114780
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 13.3 too.
^ permalink raw reply [flat|nested] 6+ messages in thread