[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: segfault with 2.18.2 from Debian 9.0 testing
From: |
Thomas Morley |
Subject: |
Re: segfault with 2.18.2 from Debian 9.0 testing |
Date: |
Tue, 27 Jun 2017 08:35:25 +0200 |
2017-06-27 6:47 GMT+02:00 David Kastrup <address@hidden>:
> Thomas Morley <address@hidden> writes:
>
>> Hi all,
>>
>> in the german forum a user reported a segfault.
>>
>> If you understand german please read:
>> https://lilypondforum.de/index.php/topic,70.0.html
>> It's too much to refer here in all details.
>>
>> In short:
>> He tried to compile
>> horn.ly from
>> www.mutopiaproject.org/ftp/MozartWA/KV447/MozartHornConcerto3/MozartHornConcerto3-lys.zip
>> with 2.18.2 which he got via apt-get from Debian 9.0 testing, "buster" i386
>> Logs under the link above in the german forum
>>
>> In the light of
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=746005#278
>> I'd recommend someone more skilled than me could have a look.
>
> Pretty sure this would be
>
> commit b0dce76daf27721ba157cd2ac5d7662d4c8d75f8
> Author: Guido Aulisi <address@hidden>
> Date: Fri Jul 22 15:26:29 2016 +0200
>
> Issue 4814: grob.cc segfaults with gcc6
>
> From the release notes of GCC 6:
>
> Optimizations remove null pointer checks for this
>
> When optimizing, GCC now assumes the this pointer can never be null,
> which is guaranteed by the language rules. Invalid programs which
> assume it is OK to invoke a member function through a null
> pointer (possibly relying on checks like this != NULL) may crash or
> otherwise fail at run time if null pointer checks are optimized
> away. With the -Wnull-dereference option the compiler tries to warn
> when it detects such invalid code.
>
> If the program cannot be fixed to remove the undefined behavior then
> the option -fno-delete-null-pointer-checks can be used to disable
> this optimization. That option also disables other optimizations
> involving pointers, not only those involving this.
>
> As a consequence, we cannot call a member function on a prospective null
> pointer (which actually is a bad idea for a number of other reasons,
> like when anything tries accessing the vtable) and then try sorting out
> the condition in the routine itself.
>
> This problem was first observed with Fedora 24. The Ubuntu GCC6
> prerelease does not show this problem; presumably the respective
> optimization has been disabled in the Ubuntu/Debian packaging because of
> affecting other programs.
>
> Commit-message-by: David Kastrup <address@hidden>
> Signed-off-by: David Kastrup <address@hidden>
>
>
> --
> David Kastrup
Do I understand correctly, 2.18.2 as distrubuted by debian 9 testing
is mostly unusable?
And they should apply the patch for 4814?
Cheers,
Harm