Package segfaults when built with -O2 but not with -O0

[Paul Howarth]

On 12/02/2011 04:12 AM, Ralf Corsepius wrote:
> On 12/01/2011 07:11 PM, Paul Howarth wrote:
>> On Thu, 01 Dec 2011 15:45:48 +0100
>> Ralf Corsepius<rc040203 at freenet.de> wrote:
>>
>>> On 12/01/2011 11:23 AM, Paul Howarth wrote:
>>>> Ralf,
>>>>
>>>> On 11/18/2011 05:53 PM, Ralf Corsepius wrote:
>>>>> On 11/18/2011 05:32 PM, Paul Howarth wrote:
>>>>>> It already builds with -Wall and there are no warnings:
>>>>> This doesn't mean much.
>>>>>
>>>>> Adding a couple of more agressive options, this is what happens to
>>>>> pptp:
>>>>>
>>>
>>>> What were the "couple of more agressive options" you used,
>>>
>>> This is what I did (rebased against today's git):
>>>
>>> diff --git a/pptp.spec b/pptp.spec
>>> index 289dd08..78e36ca 100644
>>> --- a/pptp.spec
>>> +++ b/pptp.spec
>>> @@ -86,7 +86,7 @@ tunnels.
>>> perl -pi -e 's/install -o root -m 555 pptp/install -m 755 pptp/;'
>>> Makefile
>>>
>>> %build
>>> -make %{?_smp_mflags} CFLAGS="-Wall %{optflags}" IP=/sbin/ip
>>> +make %{?_smp_mflags} CFLAGS="-Wall %{optflags} -Wextra
>>> -Wstrict-aliasing -Wnested-externs -Wstrict-prototypes" IP=/sbin/ip
>>>
>>> %install
>>> rm -rf %{buildroot}
>>>
>>>
>>>> and which
>>>> distro?
>>>
>>> Local rawhide mock.
>>>
>>> The result I posted was extracted from a "fedpkg mockbuild"'s
>>> build.log in a local mock on fedora-16/x86_64.
>>>
>>>
>>>> I've tried "-Wall -Wextra" and still can't provoke the strict
>>>> aliasing warning locally.
>>> -Wstrict-aliasing is responsible for this warning.
>>>
>>> Today's version looks like this:
>>>
>>> # grep warning: results_pptp/1.7.2/13.fc17/build.log | grep punned
>>> pptp_gre.c:92:29: warning: dereferencing type-punned pointer might
>>> break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp_gre.c:99:28: warning: dereferencing type-punned pointer might
>>> break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp_callmgr.c:202:48: warning: dereferencing type-punned pointer
>>> might break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp_callmgr.c:325:29: warning: dereferencing type-punned pointer
>>> might break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp_callmgr.c:330:28: warning: dereferencing type-punned pointer
>>> might break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp_callmgr.c:358:25: warning: dereferencing type-punned pointer
>>> might break strict-aliasing rules [-Wstrict-aliasing]
>>> pptp.c:459:33: warning: dereferencing type-punned pointer might break
>>> strict-aliasing rules [-Wstrict-aliasing]
>>
>> This is weird: I can't reproduce these either locally in mock or in
>> koji:
> Neither can I ;)
>
>> http://koji.fedoraproject.org/koji/taskinfo?taskID=3555838
>
> ... mock appends build.log's from subsequent mock runs ...
>
> ... the warnings above stem from older builds.
>
> I had not cleaned up the build.log when "git merging" your recent
> changes into my git checkout.

Hmm, that sort of explains it - except that even if I don't apply any of 
the last few patches since the F14 version, I *still* can't provoke a 
strict-aliasing warning.

Paul.