public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
@ 2022-04-21 8:46 kamilcukrowski at gmail dot com
2022-04-21 9:03 ` [Bug middle-end/105331] [11/12 Regression] " jakub at gcc dot gnu.org
` (8 more replies)
0 siblings, 9 replies; 10+ messages in thread
From: kamilcukrowski at gmail dot com @ 2022-04-21 8:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
Bug ID: 105331
Summary: -Wmaybe-uninitialized warning on va_arg with double
_Complex on va_list pointer
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: kamilcukrowski at gmail dot com
Target Milestone: ---
Passing a pointer to `va_list` to a function, and then using `va_arg` with type
`double _Complex` with derefenced pointer to `va_list` results in a false
positive `-Wmaybe-uninitailized` warning. It is a false-positive - it's a
pointer to `va_list`, the pointed-to value is just initialized by the caller.
Note that this triggers _only_ with `double _Complex` type. Neither `long
double _Complex` or `float _Complex` or `double` or any other type.
> the exact version of GCC; the options given when GCC was configured/built;
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-bootstrap
--prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-linker-build-id --enable-lto
--enable-multilib --enable-plugin --enable-shared --enable-threads=posix
--disable-libssp --disable-libstdcxx-pch --disable-werror
--with-build-config=bootstrap-lto --enable-link-serialization=1
gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.2.0 (GCC)
> the system type;
$ uname -a
Linux leonidas 5.17.1-zen1-1-zen #1 ZEN SMP PREEMPT Mon, 28 Mar 2022 21:56:46
+0000 x86_64 GNU/Linux
$ cat /etc/arch-release
Arch Linux release
> the complete command line that triggers the bug; the compiler output (error messages, warnings, etc.);
$ gcc --save-temps -O -Wmaybe-uninitialized -c example.c
example.c: In function ‘take_double_complex_to_int’:
example.c:4:38: warning: ‘va_arg_tmp.5’ may be used uninitialized
[-Wmaybe-uninitialized]
4 | return va_arg(*va, double _Complex);
| ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
> and the preprocessed file (*.i*) that triggers the bug
```
$ cat example.i
# 0 "example.c"
# 0 "<built-in>"
# 0 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 0 "<command-line>" 2
# 1 "example.c"
typedef __builtin_va_list va_list;
int take_double_complex_to_int(va_list *va) {
return __builtin_va_arg(*va, double _Complex);
}
```
--- Really, it's just:
$ cat example.c
typedef __builtin_va_list va_list;
#define va_arg(ap, type) __builtin_va_arg(ap, type)
int take_double_complex_to_int(va_list *va) {
return va_arg(*va, double _Complex);
}
--- I tested docker containers: image gcc:10 works, but image gcc:11.1.0 shows
the error :
$ dockertest() { if docker run -i --rm $1 gcc -O -Wmaybe-uninitialized -Werror
-c -xc - < example.c; then echo "$1: FINE"; else echo "$1: error"; fi; }
$ dockertest gcc:10
gcc:10 FINE
$ dockertest gcc:11
<stdin>: In function 'take_double_complex_to_int':
<stdin>:4:21: error: 'va_arg_tmp.5' may be used uninitialized
[-Werror=maybe-uninitialized]
cc1: all warnings being treated as errors
gcc:11: error
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
@ 2022-04-21 9:03 ` jakub at gcc dot gnu.org
2022-04-21 9:07 ` jakub at gcc dot gnu.org
` (7 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-21 9:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Priority|P3 |P2
Ever confirmed|0 |1
Summary|-Wmaybe-uninitialized |[11/12 Regression]
|warning on va_arg with |-Wmaybe-uninitialized
|double _Complex on va_list |warning on va_arg with
|pointer |double _Complex on va_list
| |pointer
Last reconfirmed| |2022-04-21
Component|c |middle-end
CC| |jakub at gcc dot gnu.org
Target Milestone|--- |11.4
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r11-165-geb72dc663e9070b281be83a80f6f838a3a878822
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
2022-04-21 9:03 ` [Bug middle-end/105331] [11/12 Regression] " jakub at gcc dot gnu.org
@ 2022-04-21 9:07 ` jakub at gcc dot gnu.org
2022-04-21 10:17 ` [Bug target/105331] " jakub at gcc dot gnu.org
` (6 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-21 9:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Status|NEW |ASSIGNED
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
2022-04-21 9:03 ` [Bug middle-end/105331] [11/12 Regression] " jakub at gcc dot gnu.org
2022-04-21 9:07 ` jakub at gcc dot gnu.org
@ 2022-04-21 10:17 ` jakub at gcc dot gnu.org
2022-04-21 11:03 ` rguenth at gcc dot gnu.org
` (5 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-21 10:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 52844
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52844&action=edit
gcc12-pr105331.patch
Untested fix.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (2 preceding siblings ...)
2022-04-21 10:17 ` [Bug target/105331] " jakub at gcc dot gnu.org
@ 2022-04-21 11:03 ` rguenth at gcc dot gnu.org
2022-04-21 11:06 ` jakub at gcc dot gnu.org
` (4 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-04-21 11:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
possibly other targets have copied the same pattern and thus have the same
issue (the varargs code tends to be cut&pasted)
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (3 preceding siblings ...)
2022-04-21 11:03 ` rguenth at gcc dot gnu.org
@ 2022-04-21 11:06 ` jakub at gcc dot gnu.org
2022-04-28 10:35 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-21 11:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I actually went through them all and didn't see it elsewhere (was looking for
ADDR_EXPR word inside of *gimplify_va_arg*).
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11/12 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (4 preceding siblings ...)
2022-04-21 11:06 ` jakub at gcc dot gnu.org
@ 2022-04-28 10:35 ` cvs-commit at gcc dot gnu.org
2022-04-28 10:36 ` [Bug target/105331] [11 " jakub at gcc dot gnu.org
` (2 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-04-28 10:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
--- Comment #5 from CVS 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:89dbf9a5f55e0f7565865d1b38e681ef7d76afaf
commit r12-8301-g89dbf9a5f55e0f7565865d1b38e681ef7d76afaf
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Apr 28 12:33:59 2022 +0200
i386: Fix up ix86_gimplify_va_arg [PR105331]
On the following testcase we emit a bogus
'va_arg_tmp.5' may be used uninitialized
warning. The reason is that when gimplifying the addr = &temp;
statement, the va_arg_tmp temporary var for which we emit ADDR_EXPR
is not TREE_ADDRESSABLE, prepare_gimple_addressable emits some extra
code to initialize the newly addressable var from its previous value,
but it is a new variable which hasn't been initialized yet and will
be later, so we end up initializing it with uninitialized SSA_NAME:
va_arg_tmp.6 = va_arg_tmp.5_14(D);
addr.2_16 = &va_arg_tmp.6;
_17 = MEM[(double *)sse_addr.4_13];
MEM[(double * {ref-all})addr.2_16] = _17;
and with -O1 we actually don't DSE it before the warning is emitted.
If we make the temp TREE_ADDRESSABLE before the gimplification, then
this prepare_gimple_addressable path isn't taken and we effectively
omit the first statement above and so the bogus warning is gone.
I went through other backends and didn't find another instance of this
problem.
2022-04-28 Jakub Jelinek <jakub@redhat.com>
PR target/105331
* config/i386/i386.cc (ix86_gimplify_va_arg): Mark va_arg_tmp
temporary TREE_ADDRESSABLE before trying to gimplify ADDR_EXPR
of it.
* gcc.dg/pr105331.c: New test.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (5 preceding siblings ...)
2022-04-28 10:35 ` cvs-commit at gcc dot gnu.org
@ 2022-04-28 10:36 ` jakub at gcc dot gnu.org
2022-05-06 23:44 ` cvs-commit at gcc dot gnu.org
2022-05-09 11:25 ` jakub at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-28 10:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[11/12 Regression] |[11 Regression]
|-Wmaybe-uninitialized |-Wmaybe-uninitialized
|warning on va_arg with |warning on va_arg with
|double _Complex on va_list |double _Complex on va_list
|pointer |pointer
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed on the trunk so far.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (6 preceding siblings ...)
2022-04-28 10:36 ` [Bug target/105331] [11 " jakub at gcc dot gnu.org
@ 2022-05-06 23:44 ` cvs-commit at gcc dot gnu.org
2022-05-09 11:25 ` jakub at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-05-06 23:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:65c1c480b33ea36e9505ed444eed09a0cc1c9256
commit r11-9964-g65c1c480b33ea36e9505ed444eed09a0cc1c9256
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Apr 28 12:33:59 2022 +0200
i386: Fix up ix86_gimplify_va_arg [PR105331]
On the following testcase we emit a bogus
'va_arg_tmp.5' may be used uninitialized
warning. The reason is that when gimplifying the addr = &temp;
statement, the va_arg_tmp temporary var for which we emit ADDR_EXPR
is not TREE_ADDRESSABLE, prepare_gimple_addressable emits some extra
code to initialize the newly addressable var from its previous value,
but it is a new variable which hasn't been initialized yet and will
be later, so we end up initializing it with uninitialized SSA_NAME:
va_arg_tmp.6 = va_arg_tmp.5_14(D);
addr.2_16 = &va_arg_tmp.6;
_17 = MEM[(double *)sse_addr.4_13];
MEM[(double * {ref-all})addr.2_16] = _17;
and with -O1 we actually don't DSE it before the warning is emitted.
If we make the temp TREE_ADDRESSABLE before the gimplification, then
this prepare_gimple_addressable path isn't taken and we effectively
omit the first statement above and so the bogus warning is gone.
I went through other backends and didn't find another instance of this
problem.
2022-04-28 Jakub Jelinek <jakub@redhat.com>
PR target/105331
* config/i386/i386.c (ix86_gimplify_va_arg): Mark va_arg_tmp
temporary TREE_ADDRESSABLE before trying to gimplify ADDR_EXPR
of it.
* gcc.dg/pr105331.c: New test.
(cherry picked from commit 89dbf9a5f55e0f7565865d1b38e681ef7d76afaf)
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug target/105331] [11 Regression] -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
` (7 preceding siblings ...)
2022-05-06 23:44 ` cvs-commit at gcc dot gnu.org
@ 2022-05-09 11:25 ` jakub at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-05-09 11:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105331
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2022-05-09 11:25 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-21 8:46 [Bug c/105331] New: -Wmaybe-uninitialized warning on va_arg with double _Complex on va_list pointer kamilcukrowski at gmail dot com
2022-04-21 9:03 ` [Bug middle-end/105331] [11/12 Regression] " jakub at gcc dot gnu.org
2022-04-21 9:07 ` jakub at gcc dot gnu.org
2022-04-21 10:17 ` [Bug target/105331] " jakub at gcc dot gnu.org
2022-04-21 11:03 ` rguenth at gcc dot gnu.org
2022-04-21 11:06 ` jakub at gcc dot gnu.org
2022-04-28 10:35 ` cvs-commit at gcc dot gnu.org
2022-04-28 10:36 ` [Bug target/105331] [11 " jakub at gcc dot gnu.org
2022-05-06 23:44 ` cvs-commit at gcc dot gnu.org
2022-05-09 11:25 ` jakub at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).