* [Bug tree-optimization/96367] bogus -Wformat-truncation in ILP32
2020-07-29 12:43 [Bug c/96367] New: bogus format truncation error on armhf when building perf with gcc 10 andrea.righi at canonical dot com
@ 2020-07-29 16:15 ` msebor at gcc dot gnu.org
2022-01-19 17:42 ` msebor at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: msebor at gcc dot gnu.org @ 2020-07-29 16:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96367
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |tree-optimization
Ever confirmed|0 |1
Blocks| |85741
Known to fail| |10.2.0, 11.0
Last reconfirmed| |2020-07-29
Summary|bogus format truncation |bogus -Wformat-truncation
|error on armhf when |in ILP32
|building perf with gcc 10 |
Status|UNCONFIRMED |NEW
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The mention of armhf was a helpful clue. With it I was able to reproduce an
unintended inconsistency between ILP32 and LP64 on the following test case.
Otherwise, reports without test cases to reproduce the problem are hard to
analyze. An error alone, without the context and the notes that might follow,
also isn't sufficient. Especially in this case because it doesn't show which
of the four %s directives it refers to. In the future please provide the
details requested here: https://gcc.gnu.org/bugs/#need.
$ (set -x && cat t.c && gcc -O2 -S -Wall t.c && gcc -O2 -S -Wall -m32 t.c)
+ cat t.c
char a[8];
void f (const char *s)
{
__SIZE_TYPE__ n = __builtin_strlen (s);
if (n < 3) return;
__builtin_snprintf (a, 8, "%s", s);
}
+ gcc -O2 -S -Wall t.c
+ gcc -O2 -S -Wall -m32 t.c
t.c: In function ‘f’:
t.c:8:30: warning: ‘%s’ directive output may be truncated writing between 3 and
2147483645 bytes into a region of size 8 [-Wformat-truncation=]
8 | __builtin_snprintf (a, 8, "%s", s);
| ^~
t.c:8:3: note: ‘__builtin_snprintf’ output between 4 and 2147483646 bytes into
a destination of size 8
8 | __builtin_snprintf (a, 8, "%s", s);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85741
[Bug 85741] [meta-bug] bogus/missing -Wformat-overflow
^ permalink raw reply [flat|nested] 5+ messages in thread* [Bug tree-optimization/96367] bogus -Wformat-truncation in ILP32
2020-07-29 12:43 [Bug c/96367] New: bogus format truncation error on armhf when building perf with gcc 10 andrea.righi at canonical dot com
2020-07-29 16:15 ` [Bug tree-optimization/96367] bogus -Wformat-truncation in ILP32 msebor at gcc dot gnu.org
2022-01-19 17:42 ` msebor at gcc dot gnu.org
@ 2022-09-11 21:39 ` zfigura at codeweavers dot com
2022-09-11 21:40 ` zfigura at codeweavers dot com
3 siblings, 0 replies; 5+ messages in thread
From: zfigura at codeweavers dot com @ 2022-09-11 21:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96367
Zebediah Figura <zfigura at codeweavers dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |zfigura at codeweavers dot com
--- Comment #3 from Zebediah Figura <zfigura at codeweavers dot com> ---
I believe I'm running into this trying to compile Wine. Specifically, this
snprintf statement:
https://source.winehq.org/git/wine.git/blob/wine-7.17:/dlls/ntdll/unix/system.c#l3176
is yielding this warning:
../wine/dlls/ntdll/unix/system.c: In function ‘NtQuerySystemInformation’:
../wine/dlls/ntdll/unix/system.c:3176:36: error: ‘%s’ directive output between
0 and 2147483644 bytes may cause result to exceed ‘INT_MAX’
[-Werror=format-truncation=]
3176 | snprintf( info, size, "%s%c%s%c%s%c%s", version, 0, wine_build,
0, buf.sysname, 0, buf.release );
| ^~ ~~~~~~~~~~
../wine/dlls/ntdll/unix/system.c:3176:9: note: ‘snprintf’ output between 8 and
2147483780 bytes into a destination of size 4294967295
3176 | snprintf( info, size, "%s%c%s%c%s%c%s", version, 0, wine_build,
0, buf.sysname, 0, buf.release );
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
when compiled as 32-bit, using Wine's default flags (so notably -g -O2 -m32
-Wall).
I also tried to reduce it into a simpler test case:
#include <stdio.h>
#include <string.h>
extern const char text[];
size_t func(char *buffer, size_t size)
{
size_t len = strlen(text);
snprintf(buffer, size, "text%s", text);
return len;
}
which fails similarly with "gcc -m32 -O2 -Wall".
Is there a way we can even work around this in Wine? I don't see an obvious
one, especially with no clue why the bug is even happening.
^ permalink raw reply [flat|nested] 5+ messages in thread