Thomas Morley <thomasmorle...@gmail.com> 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 <guido.aul...@gmail.com>
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 <d...@gnu.org>
Signed-off-by: David Kastrup <d...@gnu.org>
--
David Kastrup
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