On 11/04/2016 10:32 AM, Jakub Jelinek wrote:
> Hi!
>
> On Fri, Nov 04, 2016 at 10:17:31AM +0100, Martin Liška wrote:
>> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
>> index 813777d..86ce793 100644
>> --- a/gcc/gimplify.c
>> +++ b/gcc/gimplify.c
>> @@ -1678,7 +1678,9 @@ warn_switch_unreachable_r (gimple_stmt_iterator
>> *gsi_p, bool *handled_ops_p,
>> worse location info. */
>> if (gimple_try_eval (stmt) == NULL)
>> {
>> - wi->info = stmt;
>> + gimple_stmt_iterator *it = XNEW (gimple_stmt_iterator);
>> + memcpy (it, gsi_p, sizeof (gimple_stmt_iterator));
>
> That would be cleaner as *it = *gsi_p;
I know that it's kind of ugly, but as the gimple stmt is not yet added to a BB,
using
gsi_for_stmt ICEs:
/tmp/use-after-scope-switch.c:12:5: internal compiler error: Segmentation fault
switch (argc)
^~~~~~
0xe16a14 crash_signal
../../gcc/toplev.c:338
0xadf890 bb_seq_addr
../../gcc/gimple.h:1658
0xae01dd gsi_start_bb
../../gcc/gimple-iterator.h:129
0xae111f gsi_for_stmt(gimple*)
../../gcc/gimple-iterator.c:617
> That set, I fail to see
> 1) the need to use a gsi pointer in wi->info compared to stmt itself,
> you can gsi_for_stmt cheaply at any time
> 2) why is anything done about this in warn_switch_unreachable_r
> - the problem isn't related to this warning IMHO. Even
> switch (x)
> {
> case 1:
> int x;
> x = 6;
> ptr = &x;
> break;
> case 2:
> ptr = &x;
> *ptr = 7;
> break;
> }
> has the same issue and there is no switch unreachable code there, but you
> still want for -fsanitize-use-after-scope pretend it is actually:
You're right, that's not handled. I'm wondering whether it's always profitable
because when you do not reach the case 1, you're not doing a poisoning
operation?
Martin
> x_tmp = x;
> {
> int x;
> switch (x_tmp)
> {
> case 1:
> x = 6;
> ptr = &x;
> break;
> case 2:
> ptr = &x;
> *ptr = 7;
> break;
> }
> }
> and put ASAN_MARK unpoisoning before GIMPLE_SWITCH.
>
> Jakub
>
