bug#33133: 26.1.50; zlib-decompress-region too rigid

[Noam Postavsky <npostavs@gmail.com>]

Katsumi Yamaoka <yamaoka@jpl.org> writes:

> Whereas `gzip -d' does, zlib-decompress-region doesn't decompress
> corrupted data of a certain kind.  For instance, visiting
>
> https://www.gutenberg.org/no-such-page-exists
>
> using eww shows raw gzipped data.  The data extracted is attached.
> As for `gzip -d', it says "unexpected end of file" in stderr.

> If there is no prospect to improve zlib-decompress-region, how
> about this workaround?

We could have zlib-decompress-region ignore unexpected eof as well,
e.g., the below (though it should obviously be enhanced to depend on a
new parameter):

--- i/src/decompress.c
+++ w/src/decompress.c
@@ -206,7 +206,7 @@ DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
     }
   while (inflate_status == Z_OK);
 
-  if (inflate_status != Z_STREAM_END)
+  if (inflate_status != Z_STREAM_END && inflate_status != Z_BUF_ERROR)
     return unbind_to (count, Qnil);
 
   unwind_data.start = 0;