299689 2025-09-28 00:08:23 -0700 Clang 21 complains about implicit casting between char32_t and char16_t throughout the codebase 2025-10-05 00:09:15 -0700 1 1 1 Unclassified WebKit New Bugs WebKit Nightly Build Unspecified Unspecified NEW https://bugs.webkit.org/show_bug.cgi?id=299535 InRadar P2 Normal --- 1 ross.kirsling mcatanzaro darin ddkilzer mcatanzaro webkit-bug-importer oldest_to_newest 2146570 0 ross.kirsling 2025-09-28 00:08:23 -0700 As of 271373@main, we decided to turn UChar32 (i.e. int32_t) into char32_t. More recently, we've also replaced UChar with char16_t (though that part is not an issue). Clang 21 introduces `character-conversion` warnings for implicit conversion between char32_t and char16_t (in both directions, citing it "may change the meaning of the represented code unit"). Addressing this will be a similarly-sized endeavor to 271373@main itself, and unfortunately involves patching gtest too. It took a couple of hours just to get through WTF, PAL, and gtest—see attached patch. I will temporarily set `-Wno-character-conversion` for PS port just because it's blocking our deployment of extra EWS bots. 2146571 1 ross.kirsling 2025-09-28 00:12:36 -0700 I'm getting 403 Forbidden when trying to attach a patch; you can find it on Slack instead: https://webkit.slack.com/archives/CU64U6FDW/p1759041829898719?thread_ts=1758976128.172549&cid=CU64U6FDW 2146580 2 ross.kirsling 2025-09-28 01:03:30 -0700 `-Wno-character-conversion` has now been temporarily set for PS port: https://commits.webkit.org/300663@main 2146630 3 darin 2025-09-28 12:36:27 -0700 Ideally we would come up with a good way to set the warning flags based on clang version rather than platform. Dave, this new warning is coming up soon in clang 21. 2146937 4 mcatanzaro 2025-09-29 13:14:22 -0700 *** Bug 299535 has been marked as a duplicate of this bug. *** 2146977 5 mcatanzaro 2025-09-29 15:59:16 -0700 Pull request: https://github.com/WebKit/WebKit/pull/51527 2146986 6 mcatanzaro 2025-09-29 16:24:44 -0700 (In reply to Darin Adler from comment #3) > Ideally we would come up with a good way to set the warning flags based on > clang version rather than platform. WEBKIT_PREPEND_GLOBAL_COMPILER_FLAGS checks whether the flag is supported or not, so it's safe to use it unconditionally. Ross proposed this in https://github.com/WebKit/WebKit/pull/51490. 2147020 7 darin 2025-09-29 18:14:23 -0700 (In reply to Michael Catanzaro from comment #6) > WEBKIT_PREPEND_GLOBAL_COMPILER_FLAGS checks whether the flag is supported or > not, so it's safe to use it unconditionally. Ross proposed this in > https://github.com/WebKit/WebKit/pull/51490. That’s neat. Maybe we should turn off this warning immediately using WEBKIT_PREPEND_GLOBAL_COMPILER_FLAGS and then turn the warning back on while patching all the call sites to adapt to it. No reason we have to choose, we can do both! 2148519 8 webkit-bug-importer 2025-10-05 00:09:15 -0700 <rdar://problem/161980988>