276224 2024-07-04 06:55:39 -0700 [GStreamer] gstStructureGet<T> may return optionals with unitialized values on Clang 18 2024-07-04 11:54:14 -0700 1 1 1 Unclassified WebKit Platform WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 cadubentzen webkit-unassigned bugs-noreply philn webkit-bug-importer oldest_to_newest 2044675 0 cadubentzen 2024-07-04 06:55:39 -0700 On bug 275609 we introduced the gstStructureGet<T> helper. After using it in more places, we found what may be a compiler bug (reproduced it with Clang 18 so far). Given a GstStructure named structure with "a-structure, width=10". If we try: auto height = gstStructureGet<int>(structure, "height"_s); if (height) GST_LOG("height = %d", *height); although the branch shouldn't be executed since there's no "height" field. It is executed with an unitialized value. After debugging what's happening, it seems to be actually a compiler issue. Fixed it by using if(UNLIKELY(gst_structure_get_<type>)) in gstStructureGet branches. Without that, the branches were being executed and returning std::optional with unitialized values when they shouldn't. Patch for the fix in WebKit incoming. Pending on a minimal reproducer outside WebKit to confirm it's a bug in Clang... 2044682 1 philn 2024-07-04 07:27:32 -0700 *** Bug 276222 has been marked as a duplicate of this bug. *** 2044688 2 cadubentzen 2024-07-04 08:54:02 -0700 Reduced the copmpiler bug outside of WebKit at https://github.com/cadubentzen/std-optional-bug-clang 2044692 3 cadubentzen 2024-07-04 09:32:12 -0700 Pull request: https://github.com/WebKit/WebKit/pull/30493 2044717 4 ews-feeder 2024-07-04 11:53:24 -0700 Committed 280669@main (98b041523464): <https://commits.webkit.org/280669@main> Reviewed commits have been landed. Closing PR #30493 and removing active labels. 2044718 5 webkit-bug-importer 2024-07-04 11:54:14 -0700 <rdar://problem/131130985>