https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95463
Bug ID: 95463
Summary: missing -Warray-bounds caused by assuming unsigned
integer wrapping
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
GCC avoids issuing -Warray-bounds for indices whose range wraps around zero,
such as in g() below. Since unsigned wraparound is unlikely intended, issuing
a warning in these cases would be justified even if a subset of the cases is
valid.
$ cat x.c && gcc -O2 -S -Wall x.c
char a[2];
void f (unsigned i)
{
if (i > 2)
return;
a[i + 2] = 0; // -Warray-bounds (good)
}
void g (unsigned i)
{
if (i < 2) return;
a[i + 2] = 0; // missing -Warray-bounds
}
x.c: In function ‘f’:
x.c:7:4: warning: array subscript 2 is above array bounds of ‘char[2]’
[-Warray-bounds]
7 | a[i + 2] = 0; // -Warray-bounds (good)
| ~^~~~~~~
x.c:1:6: note: while referencing ‘a’
1 | char a[2];
| ^
