RE: [PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

RE: [PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

[Daniel Marjamäki]

Hello!

I am not against it..

However I think there is no danger. I see no potential use of
uninitialized variable.

The use of n_unroll is guarded by n_unroll_found.

Best regards,
Daniel Marjamäki

Re: [PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

[Kyrill Tkachov]

On 17/04/14 18:06, Daniel Marjamäki wrote:
> Hello!
>
> I am not against it..
>
> However I think there is no danger. I see no potential use of
> uninitialized variable.
>
> The use of n_unroll is guarded by n_unroll_found.

Hmmm... you're right. I guess the warning is just noise then.
I'll leave it up to maintainers to take the patch or not then.

Thanks,
Kyrill

>
> Best regards,
> Daniel Marjamäki
>

Re: [PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

[Richard Biener]

On Tue, Apr 22, 2014 at 10:07 AM, Kyrill Tkachov <kyrylo.tkachov@arm.com> wrote:
> On 17/04/14 18:06, Daniel Marjamäki wrote:
>>
>> Hello!
>>
>> I am not against it..
>>
>> However I think there is no danger. I see no potential use of
>> uninitialized variable.
>>
>> The use of n_unroll is guarded by n_unroll_found.
>
>
> Hmmm... you're right. I guess the warning is just noise then.
> I'll leave it up to maintainers to take the patch or not then.

If it only appears with the host compiler (not during bootstrap, in which
case it would break bootstrap) then we don't want it.

Richard.

> Thanks,
> Kyrill
>
>>
>> Best regards,
>> Daniel Marjamäki
>>
>
>

Re: [PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

[Jeff Law]

On 04/17/14 10:43, Kyrill Tkachov wrote:
> Hi all,
>
> While looking at the build logs I noticed a warning while building
> tree-ssa-loop-ivcanon.c about a potential use of an uninitialised variable.
> This patchlet fixes that warning by initialising it to 0.
>
> Tested arm-none-eabi.
>
> Ok for trunk?
>
> 2014-04-17  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>      * tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
>      Initialise n_unroll to 0.
So did you do a thorough analysis to verify that it was a false positive 
or that it was a valid warning?

For the former, it would be helpful if you filed a BZ.  We track these 
false positives for -Wuninitialized and do try to correct them.  If the 
latter then is using 0 for the initializer the safe thing to do?

Jeff

[PATCH] Fix uninitialised variable warning in tree-ssa-loop-ivcanon.c

[Kyrill Tkachov]

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Hi all,

While looking at the build logs I noticed a warning while building tree-ssa-loop-ivcanon.c about a potential use of an uninitialised variable.
This patchlet fixes that warning by initialising it to 0.

Tested arm-none-eabi.

Ok for trunk?

2014-04-17  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

	* tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
	Initialise n_unroll to 0.

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: tree-ssa-loop-ivcanon.patch --]
[-- Type: text/x-patch; name=tree-ssa-loop-ivcanon.patch, Size: 519 bytes --]

diff --git a/gcc/tree-ssa-loop-ivcanon.c b/gcc/tree-ssa-loop-ivcanon.c
index cdf1559..7a83b12 100644
--- a/gcc/tree-ssa-loop-ivcanon.c
+++ b/gcc/tree-ssa-loop-ivcanon.c
@@ -656,7 +656,7 @@ try_unroll_loop_completely (struct loop *loop,
 			    HOST_WIDE_INT maxiter,
 			    location_t locus)
 {
-  unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll, unr_insns;
+  unsigned HOST_WIDE_INT n_unroll = 0, ninsns, max_unroll, unr_insns;
   gimple cond;
   struct loop_size size;
   bool n_unroll_found = false;