Jeff Law <law@xxxxxxxxxx> writes:
| On 03/05/2013 12:04 PM, Lars Gullik Bjønnes wrote:
>> Jeffrey Walton <noloader@xxxxxxxxx> writes:
>>
>> | On Tue, Mar 5, 2013 at 1:41 PM, Lars Gullik Bjønnes
>> | <larsbj@xxxxxxxxxx> wrote:
>>>> I get a lot of warnings with -Og and gcc from trunk.
>>>> I do not get these warnings with any other warning level.
>>>>
>>>> This is a reduced example:
>>>> ----------
>>>> int foo(void);
>>>>
>>>> int failing(void)
>>>> {
>>>> int r;
>>>> unsigned int i;
>>>> struct h * p[3];
>>>>
>>>> for (i = 0; i < sizeof(p) / sizeof(p[0]); ++i) {
>>>> r = foo();
>>>> if (r != 0)
>>>> break;
>>>> }
>>>> return r >= 0;
>>>> }
>>>> -----------
>>>>
>>>> Compile with: gcc -Og -Wall -c fil.c
>>>>
>>>> gcc --version
>>>> gcc (GCC) 4.8.0 20130304 (experimental)
>>>>
>>>> Should I create a bug on this, or will someone else handle that?
>> | What warnings?
>>
>> $ gcc -Og -Wall -c fil.c
>> fil.c: In function ‘failing’:
>> fil.c:14:11: warning: ‘r’ may be used uninitialized in this function
>> [-Wmaybe-uninitialized]
>> return r >= 0;
>
| Without the optimizer enabled, GCC does not do the analysis to prove
| the loop always executes and thus does not know it can eliminate the
| edge from the entry block to the return block with its associated
| uninitialized use.
I see that I have a mistake in my first post, I meant to say:
I do not see this with any other _optimization_ level.
I do not get this warning with -O0, nor with -O1, only with -Og.
--
Lgb
