[Fontconfig-bugs] [Bug 103237] New: FcCacheOffsetsValid() couldn't detect broken cache file

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103237

            Bug ID: 103237
           Summary: FcCacheOffsetsValid() couldn't detect broken cache
                    file
           Product: fontconfig
           Version: 2.12
          Hardware: ARM
                OS: Linux (All)
            Status: NEW
          Severity: critical
          Priority: medium
         Component: library
          Assignee: fontconfig-bugs at lists.freedesktop.org
          Reporter: youngb.shin at samsung.com
        QA Contact: freedesktop at behdad.org

Created attachment 134807
  --> https://bugs.freedesktop.org/attachment.cgi?id=134807&action=edit
The broken cache file.

I faced an issue caused by broken cache files for fontconfig.
I don't know how fontconfig fails to generate proper caches.
But, somehow, fontconfig generated the broken cache which I attached in this
bug report.
As I know, the broken cache file should be detected by FcCache*Valid functions
and it should be regenerated.
But, the attached cache file was not caught by the *Valid functions. It caused
crash and missing font rendering issues in our platform (Tizen).
The bug raised from fontconfig 2.12.1. I found a patch for
FcCacheOffsetsValid() just after releasing 2.12.1.
But, after applying the patch, fontconfig still couldn't detect it properly.



As our investigation, font->num was 0 and font->size was 0 in
FcCacheOffsetsValid() function with the issue case.
Is this acceptable scenario? Or can I make it return with FcFalse in that
condition?
You can test the attached cache file with fc-cat. :)
(You need to change FcCacheTimeValid() function to always return FcTrue
if you want to test this cache file in random environments.)

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