Created attachment 103241 [details]
PDF Test case

This was reported in GNOME's Bugzilla:
https://bugzilla.gnome.org/show_bug.cgi?id=733402

pdftocairo crashes when trying to render the attached document.  FWIW, an older version of poppler (0.18.)0 does not have this issue.

My cairo version is 2a7f133639 (>0.12.16).

The stacktrace is as follows:
(gdb) r -png ~/Descargas/epiphany/013-crash.pdf 
Starting program: /home/gpoo/code/evince/install/bin/pdftocairo -png ~/Descargas/epiphany/013-crash.pdf
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x08053080 in CairoOutputDev::endTransparencyGroup (this=0x8087178) at CairoOutputDev.cc:1500
1500	  if (groupColorSpaceStack->next && groupColorSpaceStack->next->knockout) {
(gdb) thread apply all bt

Thread 1 (Thread 0xb74c2800 (LWP 3911)):
#0  0x08053080 in CairoOutputDev::endTransparencyGroup (this=0x8087178) at CairoOutputDev.cc:1500
#1  0x0805124a in CairoOutputDev::unsetSoftMaskFromImageMask (this=0x8087178, state=0x8244d48, baseMatrix=0x80879b4)
    at CairoOutputDev.cc:1932
#2  0xb7e6a120 in Gfx::doPatternImageMask (this=0x8087978, ref=0xbfffe0a4, str=0x8246378, width=1, height=1, invert=false, 
    inlineImg=false) at Gfx.cc:2097
#3  0xb7e6b2bc in Gfx::doImage (this=0x8087978, ref=0xbfffe0a4, str=0x8246378, inlineImg=false) at Gfx.cc:4370
#4  0xb7e703f1 in Gfx::opXObject (this=0x8087978, args=0xbfffe184, numArgs=1) at Gfx.cc:4179
#5  0xb7e5f949 in Gfx::execOp (this=0x8087978, cmd=0xbfffe324, args=0xbfffe184, numArgs=1) at Gfx.cc:903
#6  0xb7e670b0 in Gfx::go (this=0x8087978, topLevel=true) at Gfx.cc:762
#7  0xb7e6756e in Gfx::display (this=0x8087978, obj=0xbfffe414, topLevel=true) at Gfx.cc:728
#8  0xb7eb3873 in Page::displaySlice (this=0x8087da0, out=0x8087178, hDPI=72, vDPI=72, rotate=0, useMediaBox=true, crop=false, 
    sliceX=-1, sliceY=-1, sliceW=-1, sliceH=-1, printing=false, abortCheckCbk=0, abortCheckCbkData=0x0, annotDisplayDecideCbk=0, 
    annotDisplayDecideCbkData=0x0, copyXRef=false) at Page.cc:585
#9  0xb7ebc815 in PDFDoc::displayPageSlice (this=0x8087570, out=0x8087178, page=1, hDPI=72, vDPI=72, rotate=0, useMediaBox=true, 
    crop=false, printing=false, sliceX=-1, sliceY=-1, sliceW=-1, sliceH=-1, abortCheckCbk=0, abortCheckCbkData=0x0, 
    annotDisplayDecideCbk=0, annotDisplayDecideCbkData=0x0, copyXRef=false) at PDFDoc.cc:503
#10 0x0804f4c6 in renderPage (output_h=3367, output_w=2363, page_h=1615.75, page_w=1133.8599850000001, pg=1, cairoOut=0x8087178, 
    doc=0x8087570) at pdftocairo.cc:588
#11 main (argc=2, argv=0xbfffe6c4) at pdftocairo.cc:1056