Bug 464554

Description Michael Davidsaver 2015-04-13 19:05:05 EDT

Created attachment 252360 [details]
Crash w/ GTK2

We're seeing a SIGSEGV in cairo_set_operator as invoked from org.eclipse.swt.graphics.GC.setXORMode (full error log attached).

This may be related to (or the same) as bug #442223, though the crash is in a different cairo function.

From reading through GC.java for gtk there are a lot of variables effecting the code in question.  The options effecting this are GTK2 vs. GTK3 and two properties "org.eclipse.swt.internal.gtk.cairoGraphics" and "org.eclipse.swt.internal.gtk.useCairo".

The two combinations which trigger a crash are:

1) GTK2 without either explicitly property set
2) GTK2 with only "-Dorg.eclipse.swt.internal.gtk.cairoGraphics=false"

Several other combinations haven't crashed (yet).

3) GTK2 with both "-Dorg.eclipse.swt.internal.gtk.cairoGraphics=false" and "-Dorg.eclipse.swt.internal.gtk.useCairo=false"
4) GTK3 without properties set
5) GTK3 with only cairoGraphics=false
6) GTK3 with both cairoGraphics=false and useCairo=false

In the process of trying to narrow down the problem I wrote a short LD_PRELOAD hook to instrument some cairo functions (also attached).  What I think I see is cairo_set_operator() being called with pointers which either have never been returned by cairo_create() (cases 1,2) or seeing cairo_set_operator() called on pointers which have already been passed to cairo_destroy() (cases 3,4,5,6).

Of course my LD_PRELOAD is simply printing to stderr, so the ordering could be wrong if more than one thread is involved, though I don't think this is the case.

From a quick reading of the init() in GC.java I suspect the problem might be that in some code paths "data.cairo = handle" is explicitly assigned, while in others this appears not to be the case.

I can see that in other methods these two variables are used (apparently) interchangeable when invoking cairo functions.  In particular setXORMode() uses "handle" instead of "data.cairo".

Some version numbers for the application in question http://controlsystemstudio.org/

org.eclipse.platform
Version: 4.4.0.v20140925-0400
Build id: M20140925-0400