https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92381
Bug ID: 92381
Summary: missing -Warray-bounds on negative index with very
large magnitude
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: ---
More extensive testing of the fix for pr92341 reveals that yet another
optimization gets in the way of diagnosing negative out-of-bounds indices with
a very large magnitude:
$ cat b.c && gcc -O2 -S -Wall -fdump-tree-ccp1-details=/dev/stdout b.c
int f (void)
{
int *p = (int[]){ 1 };
__PTRDIFF_TYPE__ i = -__PTRDIFF_MAX__ - 1;
return p[i]; // missing warning
}
;; Function f (f, funcdef_no=0, decl_uid=1930, cgraph_uid=1, symbol_order=0)
Adding destination of edge (0 -> 2) to worklist
Simulating block 2
Visiting statement:
p_6 = &D.1933;
which is likely CONSTANT
Lattice value changed to CONSTANT &D.1933. Adding SSA edges to worklist.
marking stmt to be not simulated again
Visiting statement:
i_7 = -9223372036854775808;
which is likely CONSTANT
Lattice value changed to CONSTANT -9223372036854775808. Adding SSA edges to
worklist.
marking stmt to be not simulated again
Visiting statement:
i.0_1 = (long unsigned int) i_7;
which is likely CONSTANT
Match-and-simplified (long unsigned int) i_7 to 9223372036854775808
Lattice value changed to CONSTANT 9223372036854775808. Adding SSA edges to
worklist.
marking stmt to be not simulated again
Visiting statement:
_2 = i.0_1 * 4;
which is likely CONSTANT
Match-and-simplified i.0_1 * 4 to 0
Lattice value changed to CONSTANT 0. Adding SSA edges to worklist.
marking stmt to be not simulated again
Visiting statement:
_3 = p_6 + _2;
which is likely CONSTANT
Match-and-simplified p_6 + _2 to &D.1933
Lattice value changed to CONSTANT &D.1933. Adding SSA edges to worklist.
marking stmt to be not simulated again
Visiting statement:
_8 = *_3;
which is likely CONSTANT
Lattice value changed to VARYING. Adding SSA edges to worklist.
Visiting statement:
return _8;
No interesting values produced. Marked VARYING.
Substituting values and folding statements
Folding statement: D.1933[0] = 1;
Not folded
Folding statement: _8 = *_3;
Folded into: _8 = MEM[(int *)&D.1933];
Folding statement: D.1933 ={v} {CLOBBER};
Not folded
Folding statement: return _8;
Not folded
Removing dead stmt _3 = p_6 + _2;
Removing dead stmt _2 = i.0_1 * 4;
Removing dead stmt i.0_1 = (long unsigned int) i_7;
Removing dead stmt i_7 = -9223372036854775808;
Removing dead stmt p_6 = &D.1933;
No longer having address taken: D.1933
f ()
{
long int i;
int D.1933[1];
int * p;
int _8;
<bb 2> :
D.1933[0] = 1;
_8 = MEM[(int *)&D.1933];
D.1933 ={v} {CLOBBER};
return _8;
}
