grob.cc segfaults (with GCC6?)

[Valentin Villenave]

Greetings everybody,
I’m having a weird segfault on several regtests (and most of my own ly
files, which is annoying):

Parsing...
Interpreting music...
Preprocessing graphical objects...
Program received signal SIGSEGV, Segmentation fault.
0x0000000000496c2f in Grob::get_offset (address@hidden,
address@hidden) at grob.cc:400
400       if (dim_cache_[a].offset_)

Here are the regtests that reproduce the bug (the others compile just fine):

beam-cross-staff-slope.ly
dynamics-alignment-breaker-linebreak.ly
dynamics-alignment-breaker.ly
dynamics-alignment-breaker-order.ly
dynamics-alignment-breaker-subsequent-spanner.ly
dynamics-alignment-no-line-linebreak.ly
dynamics-alignment-no-line.ly
dynamics-context-textspan.ly
dynamics-unbound-hairpin.ly
event-listener-output.ly
fermata-rest-position.ly
font-name.ly
full-measure-rest-fermata.ly
line-arrows.ly
line-style-zigzag-spacing.ly
make-relative.ly
markup-line-thickness.ly
markup-note-grob-style.ly
metronome-mark-broken-bound.ly
minimum-length-after-break.ly
mm-rests2.ly
morgenlied.ly
mozart-hrn-3.ly
multi-measure-rest-center.ly
multi-measure-rest.ly
multi-measure-rest-spacing.ly
multi-measure-rest-text.ly
music-function-end-spanners.ly
offsets.ly
page-turn-page-breaking-repeats.ly
part-combine-a2.ly
part-combine-mmrest-apart.ly
part-combine-mmrest-shared.ly
part-combine-silence-mixed.ly
property-nested-override.ly
quote-cue-during.ly
quote-cue-event-types.ly
repeat-percent-count.ly
repeat-percent-count-visibility.ly
repeat-percent.ly
rest-positioning.ly
scheme-text-spanner.ly
skiptypesetting-multimeasurerest.ly
slur-broken-trend.ly
slur-scoring.ly
slur-tie-control-points.ly
slur-vertical-skylines.ly
spanner-after-line-breaking.ly
staff-mixed-size.ly
stem-direction.ly
stencil-scale.ly
tablature-full-notation.ly
tablature-harmonic-functions.ly
tablature-tie-spanner.ly
text-spanner-attachment-alignment.ly
text-spanner-full-rest.ly
text-spanner-override-order.ly
tie-direction-manual.ly
tie-pitched-trill.ly
trill-spanner-auto-stop.ly
trill-spanner-broken.ly
trill-spanner-chained.ly
trill-spanner-grace.ly
trill-spanner.ly
trill-spanner-pitched-consecutive.ly
trill-spanner-pitched-forced.ly
trill-spanner-pitched.ly
trill-spanner-scaled.ly

What makes is weird is that the bug happens both with my LilyPond
build (latest master branch) *and* with my distribution’s package
(Fedora repos generally have the latest development release: as of now
it’s 2.19.38 but this also happened with .37 and .36); however, GUB
packages of the exact same development release, don’t reproduce the
segfault.

Could it be because Fedora 24 is using GCC6? Here’s what gcc -v tells me:

COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/6.0.0/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,objc,obj-c++,fortran,ada,go,lto --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu --enable-plugin
--enable-initfini-array --disable-libgcj --with-isl --enable-libmpx
--enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686
--build=x86_64-redhat-linux
Thread model: posix
gcc version 6.0.0 20160305 (Red Hat 6.0.0-0.15) (GCC)

Now, granted, Fedora 24 is in a very early state and some other
programs do tend to crash from time to time (Firefox with JS-intensive
pages, for example). But LilyPond is the only one I have where such
segfaults are 100% reproducible.

Cheers,
Valentin.