246248 2022-10-08 06:18:48 -0700 [GLib] JPEG2000 decoder produces warning about maybe uninitialized variable 2022-10-18 07:35:20 -0700 1 1 1 Unclassified WebKit Images WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 aperez aperez cgarcia sabouhallawa webkit-bug-importer oldest_to_newest 1904247 0 aperez 2022-10-08 06:18:48 -0700 Caught by Clang with -Werror=conditional-uninitialized, inside JPEG2000Decoder::decode(): /app/webkit/Source/WebCore/platform/image-decoders/jpeg2000/JPEG2000ImageDecoder.cpp:546:56: error: variable 'a' may be uninitialized when used here [-Werror,-Wconditional-uninitialized] int adjustedAlpha = image->numcomps > 3 ? (a >> adjust[3]) + ((a >> (adjust[3] - 1)) % 2) : 0xFF; ^ /app/webkit/Source/WebCore/platform/image-decoders/jpeg2000/JPEG2000ImageDecoder.cpp:506:27: note: initialize the variable 'a' to silence this warning int r, g, b, a; ^ = 0 1 error generated. 1904248 1 aperez 2022-10-08 06:20:44 -0700 Now that I think of it... The mishandling of alpha might related to the decoding artifacts reported in bug #244528 (or at least be part of the issue). 1904277 2 aperez 2022-10-08 12:47:08 -0700 Pull request: https://github.com/WebKit/WebKit/pull/5166 1904278 3 aperez 2022-10-08 12:49:36 -0700 (In reply to Adrian Perez from comment #1) > Now that I think of it... The mishandling of alpha might related to the > decoding artifacts reported in bug #244528 (or at least be part of the > issue). *Narrator voice*: It wasn´t. 1904324 4 cgarcia 2022-10-09 02:21:24 -0700 I don't see how this can happen because a is initialized when image->numcomps > 3 and only used when image->numcomps > 3 too. 1906433 5 aperez 2022-10-18 06:00:45 -0700 (In reply to Carlos Garcia Campos from comment #4) > I don't see how this can happen because a is initialized when > image->numcomps > 3 and only used when image->numcomps > 3 too. I took another look at the code and you are right, but of course the compiler cannot completely reason about the code and produces a warning... so in the end I am only silencing the warning in my patch 🤦️ Still, I think we can merge it to contribute a bit to cleaner build output logs. 1906438 6 cgarcia 2022-10-18 06:14:58 -0700 Sure, it doesn't hurt, but let's change the bug title and commit message to make it clear it's not fixing anything, but just silencing a warning. 1906457 7 ews-feeder 2022-10-18 07:34:24 -0700 Committed 255674@main (9a76ccc77f6e): <https://commits.webkit.org/255674@main> Reviewed commits have been landed. Closing PR #5166 and removing active labels. 1906458 8 webkit-bug-importer 2022-10-18 07:35:20 -0700 <rdar://problem/101290537>