Hi On Mon, Dec 16, 2024 at 05:39:22PM -0500, Leo Izen wrote: [...]
> Essentially, we shouldn't be having FATE failures agree > depend on the specific > behavior of whatever zlib we link to, provided it's correct. > DEFLATE > promises certain things about its encodes, but one of the things DEFLATE > does not promise is that the same uncompressed data always encodes to the > same compressed data. When we check the CRC of e.g. PNG files, we > erroneously assume this, and we just basically never got called on it > because nearly every system uses a recent version of stock zlib. > > Anton is basically saying that if we want to compare the CRC of zlib output, > trying to compile a list of different zlib versions and making reference > files of each one doesn't really solve the underlying problem, and it's kind > of hacky. > > Solutions I can think of to this problem that solve it forever would be to > (a): not compare the checksums of encoded files with zlib chunks > OR > (b): have some sort of tool that decodes relevant zlib chunks and then run a > checksum on its output (c): implement enough of zlib ourselfs, so it can encode to a valid output (d): Find a input that encodes identically with all existing zlib variants (e): Find a input that encodes to max 2 variants and store 2 checksums I dont think (e) is the best solution, but if it works for all cases, my point is, that it is a valid solution thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Does the universe only have a finite lifespan? No, its going to go on forever, its just that you wont like living in it. -- Hiranya Peiri
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