Bug#1118385: texlive-binaries: corner-case PDF image nondeterminism

Am 19.10.2025 um 04:57 schrieb Aaron M. Ucko:

Hi Adam,

> I have found that when a PNG image's row width does not correspond to a
> whole number of bytes, the low-order bits of the last byte in each
> uncompressed row can fluctuate between pdflatex runs, at least when
> libpng can perform SIMD-assisted decompression, yielding
> nondeterministic output even when arranging to supply predetermined
> timestamps.  (Moreover, this fluctuation can affect the length of the
> resulting compressed stream, slightly shifting the file position of
> subsequent content.)
> 

Note sure, if you are subscribed to that bug in the meantime and follow 
the discussion. Meanwhile it seems to be sure, that we look at a design 
flaw in the libpng library. Norbert has forwarded the issue description 
+ reproduction instructions to [1]. I'm subscribed to the discussion and 
will follow it.

Hilmar

[1] https://github.com/pnggroup/libpng/discussions/864
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