https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453
Bug ID: 102453
Summary: buffer overflow by atomic built-ins not diagnosed
Product: gcc
Version: 12.0
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: ---
The buffer overflow by the straight assignment in f() below is diagnosed as
expected but the equivalent overflow by the atomic built-in in g() is not even
though both should be. The problem is simply that due to an oversight, the
access warnings lack support for atomic built-ins.
$ cat y.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout y.c
extern _Atomic char x;
void f (void)
{
long *p = (long*)&x;
*p = 0;
}
void g (void)
{
long *p = (long*)&x;
__atomic_store_n (p, 0, 0);
}
y.c: In function ‘f’:
y.c:7:3: warning: array subscript ‘long int[0]’ is partly outside array bounds
of ‘_Atomic char[1]’ [-Warray-bounds]
7 | *p = 0;
| ^~
y.c:1:21: note: object ‘x’ of size 1
1 | extern _Atomic char x;
| ^
;; Function f (f, funcdef_no=0, decl_uid=1979, cgraph_uid=1, symbol_order=0)
void f ()
{
<bb 2> [local count: 1073741824]:
MEM[(long int *)&x] = 0;
return;
}
;; Function g (g, funcdef_no=1, decl_uid=1983, cgraph_uid=2, symbol_order=1)
void g ()
{
<bb 2> [local count: 1073741824]:
__atomic_store_8 (&x, 0, 0); [tail call]
return;
}
