https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102919
Bug ID: 102919
Summary: spurious -Wrestrict warning for sprintf into the same
member array as argument plus offset
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
The write below by sprintf into p->a cannot overlap with the read from p->a + 2
because the length of the string at p->a + 2 is at most 1. The only it might
overlap is if the string was longer than fits in the array which would make the
sprintf call invalid for another reason: reading past the end. The -Wrestrict
instance should be avoided here.
$ cat z.c && gcc -O2 -S -Wall z.c
struct A { char a[4]; int i; };
void f (struct A *p)
{
__builtin_sprintf (p->a, "%s", p->a + 2);
}
z.c: In function ‘void f(A*)’:
z.c:5:21: warning: ‘__builtin_sprintf’ argument 3 may overlap destination
object ‘p’ [-Wrestrict]
5 | __builtin_sprintf (p->a, "%s", p->a + 2);
| ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
z.c:3:19: note: destination object referenced by ‘restrict’-qualified argument
1 was declared here
3 | void f (struct A *p)
| ~~~~~~~~~~^
