Bug 176869 – Unified JSC build triggers -Wsubobject-linkage warning

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: JavaScriptCore

[Michael Catanzaro]

I see a couple new warnings after r221954:

[505/5235] Building CXX object Source/...s/JavaScriptCore/UnifiedSource44.cpp.o
In file included from DerivedSources/JavaScriptCore/UnifiedSource44.cpp:1:0:
../../Source/JavaScriptCore/dfg/DFGLICMPhase.cpp:64:7: warning: ‘JSC::DFG::LICMPhase’ has a field ‘JSC::DFG::LICMPhase::m_data’ whose type uses the anonymous namespace [-Wsubobject-linkage]
 class LICMPhase : public Phase {
       ^~~~~~~~~
[507/5235] Building CXX object Source/...s/JavaScriptCore/UnifiedSource43.cpp.o
In file included from DerivedSources/JavaScriptCore/UnifiedSource43.cpp:2:0:
../../Source/JavaScriptCore/dfg/DFGIntegerCheckCombiningPhase.cpp:174:7: warning: ‘JSC::DFG::IntegerCheckCombiningPhase’ has a field ‘JSC::DFG::IntegerCheckCombiningPhase::m_map’ whose type uses the anonymous namespace [-Wsubobject-linkage]
 class IntegerCheckCombiningPhase : public Phase {
       ^~~~~~~~~~~~~~~~~~~~~~~~~~

Fix would be to move those two types into the anonymous namespace as well, according to gcc(1):

       -Wsubobject-linkage (C++ and Objective-C++ only)
           Warn if a class type has a base or a field whose type uses the
           anonymous namespace or depends on a type with no linkage.  If a
           type A depends on a type B with no or internal linkage, defining it
           in multiple translation units would be an ODR violation because the
           meaning of B is different in each translation unit.  If A only
           appears in a single translation unit, the best way to silence the
           warning is to give it internal linkage by putting it in an
           anonymous namespace as well.  The compiler doesn't give this
           warning for types defined in the main .C file, as those are
           unlikely to have multiple definitions.  -Wsubobject-linkage is
           enabled by default.

[Michael Catanzaro]

*** This bug has been marked as a duplicate of bug 176876 ***