Re: Error code -1073741819 with tie and tenuto

[David Kastrup]

Bernhard Kleine <address@hidden> writes:

> Am 13.11.2016 um 22:51 schrieb Simon Albrecht:
>> On 13.11.2016 22:49, Noeck wrote:
>>> Both
>>>
>>> \relative c {
>>>    <f ces' es>1~-- |
>>>    <f ces' des> |
>>> }
>>>
>>> and
>>>
>>> \relative {
>>>    <cis' e>1~-- |
>>>    <cis d> |
>>> }
>>>
>>> are compiled without problems here (2.19.49, Ubuntu 16.10, 64bit).
>>
>> OK, so it’s a bug already fixed.
>>
>> Best, Simon
> But withour knowing it!

I wouldn't say that.  This is

commit 93f3d637efbc038b837cf64fae0872e873e4f039
Author: David Kastrup <address@hidden>
Date:   Fri Sep 2 23:11:53 2016 +0200

    Issue 4965: Create and use Grob::parent_relative
    
    This function checks for the existence of a Grob parent before
    calculating a coordinate relative to it.  This should hopefully
    clean up the most relevant problems caused by issue 4814
    and the original GCC 6 optimization causing it.

fixed in 2.19.48.


Conversely, issue 4814 was addressed in 2.19.46 by

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>


and the fix was relying on incomplete analysis, making it responsible
for the damage reported here.

-- 
David Kastrup