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* [Bug c/115513] New: attribute nonstring could help with printf mistakes
@ 2024-06-16 17:32 peter at eisentraut dot org
2024-06-17 2:09 ` [Bug c/115513] " xry111 at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: peter at eisentraut dot org @ 2024-06-16 17:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115513
Bug ID: 115513
Summary: attribute nonstring could help with printf mistakes
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: peter at eisentraut dot org
Target Milestone: ---
Created attachment 58446
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58446&action=edit
test file
Consider this test program (also attached):
```
#include <stdio.h>
#include <string.h>
struct Data
{
char name[32] __attribute__((nonstring));
};
int f (struct Data *pd, const char *s)
{
strncpy(pd->name, s, sizeof pd->name);
printf("%s", pd->name); // unsafe, no warning!?!
return strlen(pd->name); // unsafe, gets a warning
}
```
Compile with, e.g.: gcc-14 -c -Wall -Wextra -O2 test.c
As per the documentation, this will warn about the strlen() call.
But it doesn't warn about the printf() call. This would be quite useful and
seems to be a gap in the warning coverage of this attribute.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/115513] attribute nonstring could help with printf mistakes
2024-06-16 17:32 [Bug c/115513] New: attribute nonstring could help with printf mistakes peter at eisentraut dot org
@ 2024-06-17 2:09 ` xry111 at gcc dot gnu.org
2024-06-17 9:59 ` peter at eisentraut dot org
2024-06-17 11:07 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: xry111 at gcc dot gnu.org @ 2024-06-17 2:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115513
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2024-06-17
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
Keywords| |diagnostic
Ever confirmed|0 |1
CC| |xry111 at gcc dot gnu.org
--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Confirmed.
But what should we do with something like `printf("%32s", pd->name);`?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/115513] attribute nonstring could help with printf mistakes
2024-06-16 17:32 [Bug c/115513] New: attribute nonstring could help with printf mistakes peter at eisentraut dot org
2024-06-17 2:09 ` [Bug c/115513] " xry111 at gcc dot gnu.org
@ 2024-06-17 9:59 ` peter at eisentraut dot org
2024-06-17 11:07 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: peter at eisentraut dot org @ 2024-06-17 9:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115513
--- Comment #2 from Peter Eisentraut <peter at eisentraut dot org> ---
(In reply to Xi Ruoyao from comment #1)
> But what should we do with something like `printf("%32s", pd->name);`?
Perhaps you mean
printf("%.32s", pd->name);
? (I don't think the minimum field width is relevant to this issue.) If so,
then yes, I think it would be good if this would be analyzed for correctness,
so that this incantation could be used for printing out these kinds of things.
(Better style might be `printf("%.*s", sizeof pd->name, pd->name);`.)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/115513] attribute nonstring could help with printf mistakes
2024-06-16 17:32 [Bug c/115513] New: attribute nonstring could help with printf mistakes peter at eisentraut dot org
2024-06-17 2:09 ` [Bug c/115513] " xry111 at gcc dot gnu.org
2024-06-17 9:59 ` peter at eisentraut dot org
@ 2024-06-17 11:07 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: xry111 at gcc dot gnu.org @ 2024-06-17 11:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115513
--- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Peter Eisentraut from comment #2)
> (In reply to Xi Ruoyao from comment #1)
> > But what should we do with something like `printf("%32s", pd->name);`?
>
> Perhaps you mean
>
> printf("%.32s", pd->name);
Yes I mean "%.32s".
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-06-16 17:32 [Bug c/115513] New: attribute nonstring could help with printf mistakes peter at eisentraut dot org
2024-06-17 2:09 ` [Bug c/115513] " xry111 at gcc dot gnu.org
2024-06-17 9:59 ` peter at eisentraut dot org
2024-06-17 11:07 ` xry111 at gcc dot gnu.org
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