Re: segfault with 2.18.2 from Debian 9.0 testing

[Thomas Morley]

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