Bug 185947 – WebKit (JavaScriptCore) compilation error with Clang ≥ 6

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Ting-Wei Lan]

Here are the error messages when compiling WebKitGTK+ 2.21.2 with Clang 6. The current WebKit trunk also has the same problem.

In file included from DerivedSources/JavaScriptCore/unified-sources/UnifiedSource26.cpp:6:
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/bytecode/CallLinkInfo.cpp:109:12: error: functional-style cast from 'CodeLocationLabel<JSInternalPtrTag>' to 'CodeLocationJump<JSInternalPtrTag>' uses deleted function
    return CodeLocationJump<JSInternalPtrTag>(m_callReturnLocationOrPatchableJump);
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/MacroAssemblerCodeRef.h:336:5: note: candidate function [with T = JSC::CodeLocationJump<26432>, $1 = void] has been explicitly deleted
    operator T() = delete;
    ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:118:14: note: candidate constructor
    explicit CodeLocationJump(MacroAssemblerCodePtr<tag> location)
             ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:115:7: note: candidate is the implicit move constructor
class CodeLocationJump : public CodeLocationCommon<tag> {
      ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:115:7: note: candidate is the implicit copy constructor
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:120:14: note: candidate constructor
    explicit CodeLocationJump(void* location)
             ^
In file included from DerivedSources/JavaScriptCore/unified-sources/UnifiedSource26.cpp:6:
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/bytecode/CallLinkInfo.cpp:115:12: error: functional-style cast from 'CodeLocationLabel<JSInternalPtrTag>' to 'CodeLocationDataLabelPtr<JSInternalPtrTag>' uses deleted function
    return CodeLocationDataLabelPtr<JSInternalPtrTag>(m_hotPathBeginOrSlowPathStart);
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/MacroAssemblerCodeRef.h:336:5: note: candidate function [with T = JSC::CodeLocationDataLabelPtr<26432>, $1 = void] has been explicitly deleted
    operator T() = delete;
    ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:177:14: note: candidate constructor
    explicit CodeLocationDataLabelPtr(MacroAssemblerCodePtr<tag> location)
             ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:174:7: note: candidate is the implicit move constructor
class CodeLocationDataLabelPtr : public CodeLocationCommon<tag> {
      ^
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:174:7: note: candidate is the implicit copy constructor
/home/lantw44/gnome/source/webkitgtk-2.21.2/Source/JavaScriptCore/assembler/CodeLocation.h:179:14: note: candidate constructor
    explicit CodeLocationDataLabelPtr(void* location)
             ^
2 errors generated.


I also tested a few other Clang versions, and the results are:

Clang 4 fails to compile with different error messages. I guess it is probably too old for C++17.
Clang 5 works fine.
Clang 6 fails to compile with the above error messages.
Clang 7 git snapshot (commit 53dc71d2945a91fde75ec241f48776fc739d2f75, date 2018-05-06) also fails to compile with the same messages as Clang 6.

[Carlos Alberto Lopez Perez]

*** This bug has been marked as a duplicate of bug 185198 ***

[David Kilzer (:ddkilzer)]

Reopening to fix the warnings from using the C++17 compiler in Clang 6.0.

We will have to fix these eventually, so we might as well do it now that we know about it in case they point to real issues.

[David Kilzer (:ddkilzer)]

(In reply to David Kilzer (:ddkilzer) from comment #2)
> Reopening to fix the warnings from using the C++17 compiler in Clang 6.0.
> 
> We will have to fix these eventually, so we might as well do it now that we
> know about it in case they point to real issues.

If Bug 185198 is going to be used to fix the Clang 6.0+ warnings, then feel free to dupe this back to Bug 185198.

[Michael Catanzaro]

Well, really only the error is reported here, it might be better to create a new bug for solving the warnings.

[Michael Catanzaro]

(In reply to Michael Catanzaro from comment #4)
> Well, really only the error is reported here, it might be better to create a
> new bug for solving the warnings.

(No warnings have been reported on Bugzilla thus far, to my knowledge.)

[Mark Lam]

<rdar://problem/40131933>

[Mark Lam]

Created attachment 343292 [details]
proposed patch.

[Mark Lam]

Thanks.  Will land once the EWS bots are green.

[WebKit Commit Bot]

Comment on attachment 343292 [details]
proposed patch.

Clearing flags on attachment: 343292

Committed r233070: <https://trac.webkit.org/changeset/233070>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.