> Thanks for the debugging.  The stream comes from within a matlab 'mat'
> file.  I maintain the scipy matlab file readers; the variables within
> these files are zlib compressed streams.

So this would be a Matlab issue, right?

>  Is there (should there be) a safe and maintained way to allow me to
> read a stream that does not return Z_STREAM_END?

Decompressor objects allow you to do that, but I cannot tell you how
"maintained" it is. If it has to be maintained, we could add an unit
test for it so that regressions get detected. It would be nice if you
could provide a very short zlib stream reproducing the issue.