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* [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow
@ 2023-10-04 18:03 stilor at att dot net
2023-10-04 22:50 ` [Bug middle-end/111696] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: stilor at att dot net @ 2023-10-04 18:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111696
Bug ID: 111696
Summary: [11/12/13/14 Regression] Spurious -Wstringop-overflow
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: stilor at att dot net
Target Milestone: ---
Created attachment 56052
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56052&action=edit
test case
The attached testcase started producing a warning beginning with commit
8d57bdadd2d9c2e5c95515ca7a583d7b407b55c4 when compiled with `-O3` (or `-O2
-ftree-slp-vectorize`). Starting with commit
2b8453c401b699ed93c085d0413ab4b5030bcdb8, vectorization is also enabled at
`-O2` and the testcase starting failing at `-O2` as well. The warning can be
reproduced at current HEAD (96557ee6a0a234821af865800d22621efa6e7390) as well.
Failure message:
$ /usr/gcc-test/bin/gcc -c -O3 -Wall -Werror stringop-overflow-bug-gcc.c
stringop-overflow-bug-gcc.c: In function ‘update’:
stringop-overflow-bug-gcc.c:25:3: error: writing 24 bytes into a region of size
16 [-Werror=stringop-overflow=]
25 | memcpy(&last->s, &cur.s, sizeof(struct nested));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
stringop-overflow-bug-gcc.c:10:17: note: destination object ‘a’ of size 16
10 | unsigned long a[2];
| ^
cc1: all warnings being treated as errors
$ /usr/gcc-test/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/gcc-test/bin/gcc
COLLECT_LTO_WRAPPER=/usr/gcc-test/libexec/gcc/x86_64-pc-linux-gnu/11.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --enable-languages=c --prefix=/usr/gcc-test
--disable-bootstrap
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.0.1 20210303 (experimental) (GCC)
The message is bogus:
- the "note" points to a member inside a structure and references that member's
size while memcpy has the whole structure as a destination.
- commenting out any of the first two statements in the update() function
removes the warning even though it has no effect on the addresses passed to
memcpy().
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/111696] [11/12/13/14 Regression] Spurious -Wstringop-overflow
2023-10-04 18:03 [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow stilor at att dot net
@ 2023-10-04 22:50 ` pinskia at gcc dot gnu.org
2023-10-04 22:55 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-10-04 22:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111696
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The vectorizer has not much to do with the warning issue except for the IR
change into FRE.
Before fre5:
_11 = &last_14(D)->s;
memcpy (_11, &cur.s, 24);
After:
vectp.7_19 = &accum_13(D)->sD.4831.aD.4827[0];
...
vectp.10_9 = &last_14(D)->sD.4831.aD.4827[0];
...
# .MEM_26 = VDEF <.MEM_12(D)>
MEM <vector(2) long unsigned intD.17> [(long unsigned intD.17 *)vectp.7_19] =
vect__5.13_24;
# .MEM_17 = VDEF <.MEM_26>
MEM <unsigned charD.31[24]> [(charD.11 * {ref-all})vectp.10_9] = MEM
<unsigned charD.31[24]> [(charD.11 * {ref-all})&curD.4832];
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/111696] [11/12/13/14 Regression] Spurious -Wstringop-overflow
2023-10-04 18:03 [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow stilor at att dot net
2023-10-04 22:50 ` [Bug middle-end/111696] " pinskia at gcc dot gnu.org
@ 2023-10-04 22:55 ` pinskia at gcc dot gnu.org
2023-10-05 7:38 ` rguenth at gcc dot gnu.org
2024-03-07 21:06 ` law at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-10-04 22:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111696
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I remember seeing this similar issue before where PRE/FRE/VN decides the two
addresses are the same (they are) but since waccess does not realize other
passes will use the restricted address still and still warn.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/111696] [11/12/13/14 Regression] Spurious -Wstringop-overflow
2023-10-04 18:03 [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow stilor at att dot net
2023-10-04 22:50 ` [Bug middle-end/111696] " pinskia at gcc dot gnu.org
2023-10-04 22:55 ` pinskia at gcc dot gnu.org
@ 2023-10-05 7:38 ` rguenth at gcc dot gnu.org
2024-03-07 21:06 ` law at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-10-05 7:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111696
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |11.5
Blocks| |88443
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88443
[Bug 88443] [meta-bug] bogus/missing -Wstringop-overflow warnings
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/111696] [11/12/13/14 Regression] Spurious -Wstringop-overflow
2023-10-04 18:03 [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow stilor at att dot net
` (2 preceding siblings ...)
2023-10-05 7:38 ` rguenth at gcc dot gnu.org
@ 2024-03-07 21:06 ` law at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: law at gcc dot gnu.org @ 2024-03-07 21:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111696
Jeffrey A. Law <law at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |law at gcc dot gnu.org
Priority|P3 |P2
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-03-07 21:06 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2023-10-04 18:03 [Bug middle-end/111696] New: [11/12/13/14 Regression] Spurious -Wstringop-overflow stilor at att dot net
2023-10-04 22:50 ` [Bug middle-end/111696] " pinskia at gcc dot gnu.org
2023-10-04 22:55 ` pinskia at gcc dot gnu.org
2023-10-05 7:38 ` rguenth at gcc dot gnu.org
2024-03-07 21:06 ` law at gcc dot gnu.org
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