Bug 183190 – Strange C++ build error in WebCore

• Component: WebCore Misc.
• Status: NEW

[Stefan Fröberg]

Hello.

Got the following error with latest git version of webkitgtk:

[ 61%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource164.cpp.o
[ 61%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource165.cpp.o
[ 61%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource166.cpp.o
[ 62%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource167.cpp.o
[ 62%] Building CXX object Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource168.cpp.o
In file included from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/bits/move.h:54:0,
                 from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/bits/nested_exception.h:40,
                 from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/exception:143,
                 from /usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/new:40,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/FastMalloc.h:24,
                 from /root/WebKit/Source/WebCore/config.h:55,
                 from /root/WebKit/Source/WebCore/bindings/js/JSTextTrackListCustom.cpp:26,
                 from /root/WebKit/build/DerivedSources/WebCore/unified-sources/UnifiedSource165.cpp:1:
/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/type_traits: In instantiation of 'struct std::is_base_of<WebCore::ScriptExecutionContext, WebCore::Document>':
/root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/TypeCasts.h:82:80:   required from 'typename WTF::match_constness<Source, Target>::type& WTF::downcast(Source&) [with Target = WebCore::Document; Source = WebCore::ScriptExecutionContext; typename WTF::match_constness<Source, Target>::type = WebCore::Document]'
/root/WebKit/Source/WebCore/bindings/js/JSWebAnimationCustom.cpp:47:49:   required from here
/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/include/g++-v7/type_traits:1512:12: error: invalid use of incomplete type 'class WebCore::Document'
     struct is_base_of
            ^~~~~~~~~~
In file included from /root/WebKit/Source/WebCore/dom/Node.h:33:0,
                 from /root/WebKit/Source/WebCore/bindings/js/JSTreeWalkerCustom.cpp:23,
                 from /root/WebKit/build/DerivedSources/WebCore/unified-sources/UnifiedSource165.cpp:3:
/root/WebKit/Source/WebCore/dom/TreeScope.h:38:7: note: forward declaration of 'class WebCore::Document'
 class Document;
       ^~~~~~~~
In file included from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/Ref.h:34:0,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/VectorTraits.h:24,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/Vector.h:38,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/text/StringImpl.h:32,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/text/UniquedStringImpl.h:29,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/text/SymbolImpl.h:28,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/JavaScriptCore/PrivateName.h:28,
                 from /root/WebKit/build/DerivedSources/ForwardingHeaders/JavaScriptCore/Identifier.h:23,
                 from /root/WebKit/build/DerivedSources/WebCore/JSDOMBindingInternalsBuiltins.h:34,
                 from /root/WebKit/build/DerivedSources/WebCore/WebCoreJSBuiltinInternals.h:39,
                 from /root/WebKit/Source/WebCore/bindings/js/JSDOMGlobalObject.h:29,
                 from /root/WebKit/Source/WebCore/bindings/js/JSDOMWrapper.h:24,
                 from /root/WebKit/build/DerivedSources/WebCore/JSTreeWalker.h:23,
                 from /root/WebKit/Source/WebCore/bindings/js/JSTreeWalkerCustom.cpp:21,
                 from /root/WebKit/build/DerivedSources/WebCore/unified-sources/UnifiedSource165.cpp:3:
/root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/TypeCasts.h: In instantiation of 'typename WTF::match_constness<Source, Target>::type& WTF::downcast(Source&) [with Target = WebCore::Document; Source = WebCore::ScriptExecutionContext; typename WTF::match_constness<Source, Target>::type = WebCore::Document]':
/root/WebKit/Source/WebCore/bindings/js/JSWebAnimationCustom.cpp:47:49:   required from here
/root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/TypeCasts.h:82:80: error: 'value' is not a member of 'std::is_base_of<WebCore::ScriptExecutionContext, WebCore::Document>'
     return static_cast<typename match_constness<Source, Target>::type&>(source);
                                                                                ^
/root/WebKit/build/DerivedSources/ForwardingHeaders/wtf/TypeCasts.h:82:12: error: invalid static_cast from type 'WebCore::ScriptExecutionContext' to type 'WTF::match_constness<WebCore::ScriptExecutionContext, WebCore::Document>::type& {aka WebCore::Document&}'
     return static_cast<typename match_constness<Source, Target>::type&>(source);
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [Source/WebCore/CMakeFiles/WebCore.dir/build.make:6081: Source/WebCore/CMakeFiles/WebCore.dir/__/__/DerivedSources/WebCore/unified-sources/UnifiedSource165.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:716: Source/WebCore/CMakeFiles/WebCore.dir/all] Error 2
make: *** [Makefile:152: all] Error 2

[Stefan Fröberg]

Also, the unstable 2.19.91 version was affected too by this but stable 2.18.6 build fine