[Bug 600108] New: fontforge crashes when building serafettin

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Summary: fontforge crashes when building serafettin

https://bugzilla.redhat.com/show_bug.cgi?id=600108

           Summary: fontforge crashes when building serafettin
           Product: Fedora
           Version: rawhide
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: medium
          Priority: low
         Component: fontforge
        AssignedTo: kevin(a)tummy.com
        ReportedBy: oget.fedora(a)gmail.com
         QAContact: extras-qa(a)fedoraproject.org
                CC: roozbeh(a)gmail.com, kevin(a)tummy.com,
                    fonts-bugs(a)lists.fedoraproject.org
    Classification: Fedora


Description of problem:
Crash when building serafettin cartoon fonts

Version-Release number of selected component (if applicable):
fontforge-20100501-1.fc13.x86_64

How reproducible:
always

Steps to Reproduce:
wget
http://downloads.sourceforge.net/serafettin/serafettin-cartoon-fonts-0.5....
tar jxvf serafettin-cartoon-fonts-0.5.1.tar.bz2
cd serafettin-cartoon-fonts-0.5.1
fontforge sfd2bold.ff serafettin-cartoon.sfd GPLv2+ 0.5.1

Actual results:
segfault. backtrace attached

Expected results:
build the font, or at least give some error if there is something wrong with
the font sources

Additional info:
Upstream informed:
   http://sourceforge.net/mailarchive/forum.php?forum_name=fontforge-devel
See the thread: [Fontforge-devel] crash when building serafettin

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[Bug 600108] fontforge crashes when building serafettin

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https://bugzilla.redhat.com/show_bug.cgi?id=600108

--- Comment #1 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-06-03
19:43:50 EDT ---
Created an attachment (id=421069)
 --> (https://bugzilla.redhat.com/attachment.cgi?id=421069)
The backtrace

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[Bug 600108] fontforge crashes when building serafettin

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https://bugzilla.redhat.com/show_bug.cgi?id=600108

Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |599785

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[Bug 600108] fontforge crashes when building serafettin

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https://bugzilla.redhat.com/show_bug.cgi?id=600108

Paul Flo Williams <paul(a)frixxon.co.uk&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |paul(a)frixxon.co.uk

--- Comment #2 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-06-30 05:15:41 EDT
---
Just a question and a few data points.

Firstly, was this a scratch build? This bug has been reported against a version
that doesn't appear in the updates for F13.

Nevertheless, from the backtrace we see that the crash occurred in
HideStrokePointsCircle(), which is in splinestroke.c.

I can confirm that Serafettin builds OK with FontForge 20090923 (i.e. the
version currently in F13). The boldening algorithm throws a lot of warnings,
but no crashes.

splinestroke.c was at version 1.46 at that time.

FontForge 20100501 included splinestroke.c version 1.56.

I can confirm oget's finding of a crash in this version. (Built direct from the
tarball, as I couldn't find this RPM.)

A new algorithm for stroking splines had been introduced between the two
releases (at splinestroke.c version 1.48), and the CVS log shows quite a few
oopses being fixed since that time.

splinestroke.c is now at version 1.62 in CVS.

Unless someone else get there first, I'll try the current CVS version of
FontForge tonight, but I wouldn't be surprised if this crash has already been
fixed in CVS.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #3 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-06-30 13:18:59 EDT
---
Created an attachment (id=428049)
 --> (https://bugzilla.redhat.com/attachment.cgi?id=428049)
Single character from font that demonstrates problem

Today's pull from FontForge CVS still crashes with this font. I've now managed
to isolate a single character from Serafettin that will reliably crash
FontForge, and I've attached the SFD here.

The SFD contains just the right-hand half of the character U+0B94.
1. Open FontForge with this font
2. Select U+0B94
3. Select Expand Stroke

It seems that any combination of stroke width, line join and line cap will
crash FontForge, including the default set.

I've sent another email to the upstream mailing list with the same attachment.

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[Bug 600108] fontforge crashes when building serafettin

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Kevin Fenzi <kevin(a)tummy.com&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #4 from Kevin Fenzi <kevin(a)tummy.com&gt; 2010-07-04 15:08:07 EDT ---
Excellent work Paul. ;)

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #5 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-07-25
16:10:06 EDT ---
*sigh* this is still not fixed upstream. I confirmed that U+0B94 leads to a
crash. However, I removed U+0B94 and all the other glpyhs that look like the
right half of U+0B94. Fontforge still crashes. So there are other offending
glyphs too. 

Paul, how did you trace it down to this glyph? I will just "fix" the other bad
glyphs.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #6 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-07-26 07:41:07 EDT
---
To track down the glyph, I just changed FVStrokeItScript() to print the glyph
name being processed at the time of the crash.

Since then, I've been tracking the changes in CVS and running serafettin's
scripts against the font each time.

I hadn't tried to identify any other crashing glyphs because I was hoping that
a fix for that one, when it's found, would apply to all. I haven't investigated
why the new spline-stroking algorithm is failing because the overlap code is in
flux in CVS and I'm hoping George will fix it before I hunt it down!

I can produce a list of the other bad glyphs if you like, but it won't be until
tomorrow evening. (Feel free to email me for progress.) Or, I could start
trying to fix the crash.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #7 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-07-28 04:32:36 EDT
---
Created an attachment (id=434948)
 --> (https://bugzilla.redhat.com/attachment.cgi?id=434948)
Patch to reveal failing glyphs

The list of failing glyphs is: cent, uni0B94, uni0BB0, uni0BB3, uni0BBE,
uni0BC0, uni0BCC and uni0BD7.

Not all of these crash during all transformations, and some transformations
don't produce any failures.

I've built FontForge from the 20100501 sources and patched the routine that
crashes so that it will return prematurely on finding the error condition.

Note that the patch is *simply to stop FontForge crashing*. I have no idea
whether this is part of the proper fix.

Orcan, if you have time, it would be worth seeing whether this patch produces
usable fonts as an end result. If the affected glyphs look OK, then I'll nudge
upstream to see if this patch is reasonable. If this breaks the affected
glyphs, then this crash is simply the result of some fault elsewhere, and you
may have to remove glyphs until upstream produces a proper fix.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #9 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-08-01
23:15:42 EDT ---
Sorry, I was buried under the python-2.7 rebuilds for the last few days. I'll
get back to this bug over this week.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #10 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-08-02 16:55:22 EDT
---
I've had another good look at Serafettin and I can see why FontForge has such a
hard time with it. If we validate:

Validation SerafettinCartoon ...Failed
  Self Intersecting Glyph
  Wrong Direction
  Flipped Reference
  Missing Points at Extrema
  More references in a glyph than specified in 'maxp'
  References nested more deeply than specified in 'maxp'
  Non integral coordinates in a glyph
  Two glyphs have the same name.
  Two glyphs have the unicode.
  Overlapping hints in a glyph.

There are several interesting lines here, but the most important for this bug
appears to be "self intersecting glyph". If you go into FontForge and validate,
you'll find a lot of glyphs that don't appear to be self-intersecting, but if
you look at the SFD source, it will be clear that there are a lot of points on
top of one another. These don't have any effect on the drawn outline, but they
mess with FontForge's ability to determine the direction of each part of the
contour when stroking the lines in order to expand or contract them.

Long story short, run the base font through FontForge and clean up the glyphs.
For both serafettin-cartoon.sfd and serafettin-cartoon-italic.sfd:
1. Edit -> Select -> Select All
2. Element -> Simplify -> Cleanup Glyph
3. Go to glyph "cent" (the second one with this name, U+0BBF). Remove dots that
are disconnected from main glyph
4. Go to glyph uni0BC0. Do same as above (there are two of them here).

This should allow Serafettin to build. (Works for me with upstream CVS head,
haven't tried Rawhide).

There are several glyphs with the same name in this font as well, and a few
that are mapped to the same Unicode point. I don't understand how this came
about, but they will need correcting too.

Kevin: FontForge may be fragile when dealing with this font, but in fairness it
*did* produce a big bunch of relevant warnings! I will send the relevant line
of my patch upstream for the sake of robustness.

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[Bug 600108] fontforge crashes when building serafettin

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--- Comment #11 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-08-02
18:25:57 EDT ---
Oh geez. Thanks for all your work.

Honestly, I don't want to deal with a similar problem on the next fontforge
update. Maybe I should just drop those glyphs. I kept them in when I forked
this font from another project, just to have more coverage, but I can't even
support them since I don't even read that language. Maybe if I have a co-author
in the future, who wants to support those glyphs, we can add them back.

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--- Comment #12 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-08-08
22:58:16 EDT ---
Hey Paul, if you really want to fix those glyphs, be my guest. I have committed
the sources to sourceforge svn:
   http://serafettin.svn.sourceforge.net/viewvc/serafettin/
Do you have a sourceforge account? If so, give me your username, so I can grant
you svn write access.

If you think it is too much work, let me know, and I will remove those glyphs.

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--- Comment #13 from Orcan 'oget' Ogetbil <oget.fedora(a)gmail.com&gt; 2010-08-22
16:01:21 EDT ---
I released serafettin-cartoon-fonts-0.6 with Paul's clean-ups and built RPMs
for F-12, F-13 and F-14. Now to build serafettin, I don't need this fontforge
bug fixed anymore. 

Shall we keep this open or close it WONTFIX?

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--- Comment #14 from Paul Flo Williams <paul(a)frixxon.co.uk&gt; 2010-08-22 16:17:09 EDT
---
There is a single line change that can stop FontForge from crashing that I have
still not submitted upstream because I'm not sure whether it's the right fix.
However, I will do that (I know, second time I've said that.)

With Serafettin fixed, we have no means of reproducing this in Fedora and I
suggest WONTFIX, as some form of the patch will appear upstream later. (If it
occurs again in Fedora before that time, then we can carry the patch locally.)

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Kevin Fenzi <kevin(a)tummy.com&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |CLOSED
         Resolution|                            |WONTFIX
        Last Closed|                            |2010-08-22 19:25:26

--- Comment #15 from Kevin Fenzi <kevin(a)tummy.com&gt; 2010-08-22 19:25:26 EDT ---
I'd be fine with closing it now... if it re-occurs we can reopen or file a new
one. 

Thanks guys!

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