Commits on May 31, 2020

1. WIP: blob-private.h: add CheckWriteBlob* …

   TODO:
   
   - Get rid of perror()
   - Pick proper function name for each macro (not literal WriteBlob*)

   

   MerlijnWajer committed May 31, 2020
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2. blob-private.h: throw exception instead of perror

   

   MerlijnWajer committed May 31, 2020
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3. coders/bmp: use macros for WriteBlob checks

   

   MerlijnWajer committed May 31, 2020
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4. coders/pnm: return status in WritePNMImage …

   Previously the code would always just return MagickTrue, even if it had
   just inferred that the processing failed. This is required for more
   elegant error handling throughout the function, such as checks on the
   WriteBlob() calls, where the return value is currently being ignored.
   
   Upon WriteBlob errors, we can then set the status to MagickFalse, and
   break.

   

   MerlijnWajer committed May 31, 2020
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5. coders/pnm: stop on WriteBlob failures …

   In WritePNMImage, when converting to a PNM image, the result of the
   WriteBlob calls is not checked, and instead ignored explicitly by
   '(void)' in front of it. This means that ImageMagick return success on
   images that get truncated when write(2) fails with ENOSPC.
   
   Evident by this sequence:
   
       $ ls -lsh /tmp/0009-1-small.png
       20M -rw-r--r-- 1 merlijn merlijn 20M May 25 23:59 /tmp/0009-1-small.png
       $ sudo mkdir /mnt/test
       $ sudo mount -t tmpfs none -o size=1G /mnt/test/
       $ df -h /mnt/test/
       Filesystem      Size  Used Avail Use% Mounted on
       none            5.0M     0  5.0M   0% /mnt/test
       $ convert /tmp/0009-1-small.png /mnt/test/0009.pnm
       $ echo $?
       0
       $ ls -lsh /mnt/test/0009.pnm
       5.0M -rw-r--r-- 1 merlijn merlijn 5.0M May 31 11:42 /mnt/test/0009.pnm
   
   Failure is evident with strace:
   
       write(5, "\373\372\367\373\371\367\372\370\365\372\370\364\372\370\364\372\371\366\372\367\363\363\355\346\351\344\327\370\363\356\372\370"..., 8192) = -1 ENOSPC (No space left on device)
   
   MagickCore/blob.c handles these errors nicely, but the callers of
   WriteBlob should still check the actual amount of written bytes.
   Since MagickCore/blob.c already handles EINTR for them, the checks are
   simple. This commit only fixes up the PNM image writing, but similar
   issues remain throughout the file.

   

   MerlijnWajer committed May 31, 2020
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6. coders/pnm: use macros for WriteBlob checks

   

   MerlijnWajer committed May 31, 2020
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7. coders/pnm: use exception instead of perror

   

   MerlijnWajer committed May 31, 2020
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