https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92936
Bug ID: 92936
Summary: missing warning on a past-the-end store to a PHI
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: ---
Out of bounds stores to destinations that are the results of conditionals like
the one in g() below are not diagnosed. They should be both by -Warray-bounds
and by -Wstringop-overflow (without duplicates) but they're not because PHI
expressions aren't handled.
$ cat b.c && gcc -O2 -S -Wall b.c
void sink (void*);
void f (int n)
{
char a3[3], a5[5], *p;
if (n <= 3)
{
n = 3;
p = a3;
p[n] = 0; // -Warray-bounds
}
else
{
n = 5;
p = a5;
p[n] = 0; // -Warray-bounds
}
sink (p);
}
void g (int n)
{
char a3[3], a5[5], *p;
if (n <= 3)
{
n = 3;
p = a3;
}
else
{
n = 5;
p = a5;
}
p[n] = 0; // missing warning
p[n + 1] = 1; // missing warning
p[n + 9] = 2; // missing warning
p[12345] = 3; // missing warning
sink (p);
}
b.c: In function ‘f’:
b.c:17:8: warning: array subscript 5 is outside array bounds of ‘char[5]’
[-Warray-bounds]
17 | p[n] = 0; // -Warray-bounds
| ~^~~
b.c:5:15: note: while referencing ‘a5’
5 | char a3[3], a5[5], *p;
| ^~
b.c:11:8: warning: array subscript 3 is outside array bounds of ‘char[3]’
[-Warray-bounds]
11 | p[n] = 0; // -Warray-bounds
| ~^~~
b.c:5:8: note: while referencing ‘a3’
5 | char a3[3], a5[5], *p;
| ^~
