https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77627
Bug ID: 77627
Summary: Unexpected void * dereference in uninit warning (and
missed out-of-bounds warning)
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: fw at gcc dot gnu.org
Target Milestone: ---
This snippet, derived from code provided by Ron Garret:
int main(int argc, char* argv[]) {
int x[100] = {0};
int y = x[101];
int z = *(x+102);
return y+z;
}
results in the following warning:
t.c: In function ‘main’:
t.c:3:12: warning: array subscript is above array bounds [-Warray-bounds]
int y = x[101];
~^~~~~
t.c:4:7: warning: ‘*((void *)&x+408)’ is used uninitialized in this function
[-Wuninitialized]
int z = *(x+102);
^
The expression *((void *)&x+408) looks rather out of place. C programmers do
not expect that void * pointers can be dereferenced in this way.
GCC clearly realizes that the subscript is out of bounds, so perhaps it would
be possible to issue an out-of-bounds warning for this case, too.
