On Thu, 2015-04-16 at 13:55 +0200, Richard Biener wrote:
> The following applies the patch produced earlier this year, applying
> TLC to array bound warnings and catching a few more cases.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
>
> Richard.
>
> 2015-04-16 Richard Biener <[email protected]>
>
> PR tree-optimization/64277
> * tree-vrp.c (check_array_ref): Fix anti-range handling,
> simplify upper bound handling.
> (search_for_addr_array): Simplify.
> (check_array_bounds): Handle ADDR_EXPRs here.
> (check_all_array_refs): Simplify.
This caused an interesting build failure of glibc when using the latest
GCC. Here is a cut down case from elf/dl-open.c:
extern void foo(void);
struct s { int n; } v[1];
int bar (int i)
{
if ((i != 0 && i != -1 && i != -2) && (v[i].n == 0))
foo ();
return 0;
}
int baz (int i)
{
if ((i != 0 && i != -2) && (v[i].n == 0))
foo ();
return 0;
}
When compiled with -O2 -Wall -Werror, I now get an error about v[i]
being out-of-bounds in bar. But I do not get this error in baz (where
we don't check for -1. In reality, in glibc, we know that i can only be
0, -1, or -2. GCC of course doesn't know that. Does this error/warning
seem right? The difference in behavior between bar and baz seems odd.
Steve Ellcey
[email protected]
