Author: Fabian Parzefall Date: 2024-09-05T12:39:39-07:00 New Revision: 53d5ffea6be7216589599b6415c021f8bd13cd37
URL: https://github.com/llvm/llvm-project/commit/53d5ffea6be7216589599b6415c021f8bd13cd37 DIFF: https://github.com/llvm/llvm-project/commit/53d5ffea6be7216589599b6415c021f8bd13cd37.diff LOG: [clang] Check inline defs when emitting speculative vtable (#100785) Clang should only emit an available_externally vtable when there are no unused virtual inline functions. Currently, if such such a function is declared without inline inside the class, but is defined inline outside the class, Clang might emit the vtable as available_externally. This happens because Clang only considers the declarations of vtable entries, but not the definitions. This patch addresses this by inspecting the definitions in addition to the declarations. Added: Modified: clang/lib/CodeGen/ItaniumCXXABI.cpp clang/test/CodeGenCXX/vtable-available-externally.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp index 0cde8a192eda08..fb1eb72d9f3404 100644 --- a/clang/lib/CodeGen/ItaniumCXXABI.cpp +++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp @@ -442,7 +442,10 @@ class ItaniumCXXABI : public CodeGen::CGCXXABI { continue; const CXXMethodDecl *Method = VtableComponent.getFunctionDecl(); - if (!Method->getCanonicalDecl()->isInlined()) + const FunctionDecl *FD = Method->getDefinition(); + const bool IsInlined = + Method->getCanonicalDecl()->isInlined() || (FD && FD->isInlined()); + if (!IsInlined) continue; StringRef Name = CGM.getMangledName(VtableComponent.getGlobalDecl()); @@ -2279,8 +2282,18 @@ bool ItaniumCXXABI::canSpeculativelyEmitVTableAsBaseClass( if (CGM.getCodeGenOpts().ForceEmitVTables) return true; - // If we don't have any not emitted inline virtual function then we are safe - // to emit an available_externally copy of vtable. + // A speculative vtable can only be generated if all virtual inline functions + // defined by this class are emitted. The vtable in the final program contains + // for each virtual inline function not used in the current TU a function that + // is equivalent to the unused function. The function in the actual vtable + // does not have to be declared under the same symbol (e.g., a virtual + // destructor that can be substituted with its base class's destructor). Since + // inline functions are emitted lazily and this emissions does not account for + // speculative emission of a vtable, we might generate a speculative vtable + // with references to inline functions that are not emitted under that name. + // This can lead to problems when devirtualizing a call to such a function, + // that result in linking errors. Hence, if there are any unused virtual + // inline function, we cannot emit the speculative vtable. // FIXME we can still emit a copy of the vtable if we // can emit definition of the inline functions. if (hasAnyUnusedVirtualInlineFunction(RD)) diff --git a/clang/test/CodeGenCXX/vtable-available-externally.cpp b/clang/test/CodeGenCXX/vtable-available-externally.cpp index a57eb39edfe102..ab105260bc75aa 100644 --- a/clang/test/CodeGenCXX/vtable-available-externally.cpp +++ b/clang/test/CodeGenCXX/vtable-available-externally.cpp @@ -250,28 +250,39 @@ struct C : A { virtual void car(); }; +// Inline definition outside body, so we can't emit vtable available_externally +// (see previous). +// CHECK-TEST10-DAG: @_ZTVN6Test101FE = external unnamed_addr constant +struct F : A { + void foo(); + virtual void cat(); // inline outside body +}; +inline void F::cat() {} + // no key function, vtable will be generated everywhere it will be used // CHECK-TEST10-DAG: @_ZTVN6Test101EE = linkonce_odr unnamed_addr constant // CHECK-FORCE-EMIT-DAG: @_ZTVN6Test101EE = linkonce_odr unnamed_addr constant struct E : A {}; -void g(A& a) { +void h(A& a) { a.foo(); a.bar(); } -void f() { +void g() { A a; - g(a); + h(a); B b; - g(b); + h(b); C c; - g(c); + h(c); D d; - g(d); + h(d); E e; - g(e); + h(e); + F f; + h(f); } } // Test10 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
