299535 2025-09-25 11:02:23 -0700 Many -Wcharacter-conversion warnings with Clang 21 2025-09-29 13:14:22 -0700 1 1 1 Unclassified WebKit Web Template Framework WebKit Nightly Build PC Linux RESOLVED DUPLICATE 299689 https://bugs.webkit.org/show_bug.cgi?id=299720 https://bugs.webkit.org/show_bug.cgi?id=299689 P2 Normal --- 1 mcatanzaro mcatanzaro kkinnunen mcatanzaro oldest_to_newest 2145903 0 mcatanzaro 2025-09-25 11:02:23 -0700 For example: /home/mcatanzaro/Projects/WebKit/Source/WTF/wtf/text/StringConcatenate.h:112:30: error: implicit conversion from 'const char32_t' to 'element_type' (aka 'char16_t') may lose precision and change the meaning of the represented code unit [-Werror,-Wcharacter-conversion] 112 | destination[0] = m_character; | ~ ^~~~~~~~~~~ 1 error generated. /home/mcatanzaro/Projects/WebKit/Source/WTF/wtf/URLHelpers.cpp:174:61: error: implicit conversion from 'char16_t' to 'char32_t' may change the meaning of the represented code unit [-Werror,-Wcharacter-conversion] 174 | return isLookalikeCharacterOfScriptType<ScriptType>(first) && !(isOfScriptType<ScriptType>(second) || isASCIIDigitOrValidHostCharacter(second)); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~~~~ /home/mcatanzaro/Projects/WebKit/Source/WTF/wtf/URLHelpers.cpp:177:48: error: implicit conversion from 'char32_t' to 'char16_t' may lose precision and change the meaning of the represented code unit [-Werror,-Wcharacter-conversion] 177 | || isLookalikePair(*previousCodePoint, codePoint); | ~~~~~~~~~~~~~~~ ^~~~~~~~~ /home/mcatanzaro/Projects/WebKit/Source/WTF/wtf/URLHelpers.cpp:350:16: note: in instantiation of function template specialization 'WTF::URLHelpers::isLookalikeSequence<USCRIPT_ARMENIAN>' requested here 350 | return isLookalikeSequence<USCRIPT_ARMENIAN>(previousCodePoint, codePoint) | ^ Worse, several of these are coming from ICU headers: /home/mcatanzaro/Projects/WebKit/Source/WTF/wtf/text/StringView.h:1017:5: error: implicit conversion from 'const char16_t' to 'char32_t' may change the meaning of the represented code unit [-Werror,-Wcharacter-conversion] 1017 | U16_GET(static_cast<const char16_t*>(m_current), 0, 0, length, codePoint); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /usr/include/unicode/utf16.h:202:9: note: expanded from macro 'U16_GET' 202 | (c)=(s)[i]; \ | ~^~~~~~ 2145904 1 mcatanzaro 2025-09-25 11:11:09 -0700 Fixing ICU is pretty easy: diff --git a/icu4c/source/common/unicode/utf16.h b/icu4c/source/common/unicode/utf16.h index 3902c60e95e..43e72a711cc 100644 --- a/icu4c/source/common/unicode/utf16.h +++ b/icu4c/source/common/unicode/utf16.h @@ -165,7 +165,7 @@ * @stable ICU 2.4 */ #define U16_GET_UNSAFE(s, i, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[i]; \ + (c)=(UChar32)(s)[i]; \ if(U16_IS_SURROGATE(c)) { \ if(U16_IS_SURROGATE_LEAD(c)) { \ (c)=U16_GET_SUPPLEMENTARY((c), (s)[(i)+1]); \ @@ -199,7 +199,7 @@ * @stable ICU 2.4 */ #define U16_GET(s, start, i, length, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[i]; \ + (c)=(UChar32)(s)[i]; \ if(U16_IS_SURROGATE(c)) { \ uint16_t __c2; \ if(U16_IS_SURROGATE_LEAD(c)) { \ @@ -238,7 +238,7 @@ * @stable ICU 60 */ #define U16_GET_OR_FFFD(s, start, i, length, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[i]; \ + (c)=(UChar32)(s)[i]; \ if(U16_IS_SURROGATE(c)) { \ uint16_t __c2; \ if(U16_IS_SURROGATE_LEAD(c)) { \ @@ -279,7 +279,7 @@ * @stable ICU 2.4 */ #define U16_NEXT_UNSAFE(s, i, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[(i)++]; \ + (c)=(UChar32)(s)[(i)++]; \ if(U16_IS_LEAD(c)) { \ (c)=U16_GET_SUPPLEMENTARY((c), (s)[(i)++]); \ } \ @@ -307,7 +307,7 @@ * @stable ICU 2.4 */ #define U16_NEXT(s, i, length, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[(i)++]; \ + (c)=(UChar32)(s)[(i)++]; \ if(U16_IS_LEAD(c)) { \ uint16_t __c2; \ if((i)!=(length) && U16_IS_TRAIL(__c2=(s)[(i)])) { \ @@ -339,7 +339,7 @@ * @stable ICU 60 */ #define U16_NEXT_OR_FFFD(s, i, length, c) UPRV_BLOCK_MACRO_BEGIN { \ - (c)=(s)[(i)++]; \ + (c)=(UChar32)(s)[(i)++]; \ if(U16_IS_SURROGATE(c)) { \ uint16_t __c2; \ if(U16_IS_SURROGATE_LEAD(c) && (i)!=(length) && U16_IS_TRAIL(__c2=(s)[(i)])) { \ However, unfortunately ICU has a contributor license agreement, which I'm not going to accept, so I won't submit this to upstream. We need to work around this at the WebKit level anyway since we only control the ICU headers on macOS; on Linux, they are a system dependency. 2145919 2 mcatanzaro 2025-09-25 12:20:08 -0700 Unrelated: /home/mcatanzaro/Projects/WebKit/WebKitBuild/gtk4/JavaScriptCore/PrivateHeaders/JavaScriptCore/RemoteInspector.h:135:13: error: virtual method '~RemoteInspector' is inside a 'final' class and can never be overridden [-Werror,-Wunnecessary-virtual-specifier] 135 | virtual ~RemoteInspector(); | ^ 1 error generated. 2146870 3 mcatanzaro 2025-09-29 10:00:35 -0700 Darin says: "I reviewed ICU documentation, and I think it’s an error to use U16_GET with char32_t. The output type is supposed to be uint32_t. So that’s why ICU won’t be fixing it!" Well, the actual output type is UChar32. It should be compatible with char32_t in the sense that casting should do the right thing, but it's indeed WebKit's fault for using the wrong type, not an ICU bug. So no need for anybody to try submitting my patch to ICU. 2146930 4 mcatanzaro 2025-09-29 13:08:56 -0700 Another note for myself: /home/mcatanzaro/Projects/WebKit/Source/WebKit/UIProcess/AuxiliaryProcessProxy.cpp:166:10: error: variable 'varname' is used uninitialized whenever switch case is taken [-Werror,-Wsometimes-uninitialized] 166 | case ProcessLauncher::ProcessType::DBusProxy: | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /home/mcatanzaro/Projects/WebKit/Source/WebKit/UIProcess/AuxiliaryProcessProxy.cpp:171:43: note: uninitialized use occurs here 171 | const char* processCmdPrefix = getenv(varname); | ^~~~~~~ /home/mcatanzaro/Projects/WebKit/Source/WebKit/UIProcess/AuxiliaryProcessProxy.cpp:147:24: note: initialize the variable 'varname' to silence this warning 147 | const char* varname; | ^ | = nullptr 2146936 5 mcatanzaro 2025-09-29 13:14:22 -0700 *** This bug has been marked as a duplicate of bug 299689 ***