llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Tom Honermann (tahonermann) <details> <summary>Changes</summary> Lifetime extended temporary objects that are bound to references with static storage duration may have external linkage and therefore require mangled symbol names. Clang uses an extension of the Microsoft ABI to give these symbols an implicit name of '$RT' followed by a discriminator and then mangles them similarly to the variable they are bound to. Clang's mangling scheme differs from the one used by MSVC. Previously, the `$RT<discriminator>` portion of the name was not registered as a back reference candidate and this resulted in incorrect back references for enclosing class and/or namespace scopes that might be referenced in the type of the object. This is an ABI change and has the potential to cause backward compatibility issues with previous Clang releases. Since MSVC uses a different mangling scheme, this change does not affect compatibility with MSVC. This fixes one of the name mangling concerns reported in #<!-- -->85423. --- Full diff: https://github.com/llvm/llvm-project/pull/85529.diff 3 Files Affected: - (modified) clang/docs/ReleaseNotes.rst (+6) - (modified) clang/lib/AST/MicrosoftMangle.cpp (+2-1) - (modified) clang/test/CodeGenCXX/mangle-ms-back-references.cpp (+13) ``````````diff diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 1ae35e6881d2f8..f0da6ca497b575 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -54,6 +54,12 @@ ABI Changes in This Version inline member function that contains a static local variable with a dynamic initializer is declared with ``__declspec(dllimport)``. (#GH83616). +- Fixed Microsoft name mangling of lifetime extended temporary objects. This + change corrects missing back reference registrations that could result in + incorrect back reference indexes and suprising demangled name results. Since + MSVC uses a different mangling for these objects, compatibility is not affected. + (#GH85423). + AST Dumping Potentially Breaking Changes ---------------------------------------- diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp index aa26bb7ed46f48..cf9c2093a8f6a1 100644 --- a/clang/lib/AST/MicrosoftMangle.cpp +++ b/clang/lib/AST/MicrosoftMangle.cpp @@ -3911,7 +3911,8 @@ void MicrosoftMangleContextImpl::mangleReferenceTemporary( msvc_hashing_ostream MHO(Out); MicrosoftCXXNameMangler Mangler(*this, MHO); - Mangler.getStream() << "?$RT" << ManglingNumber << '@'; + Mangler.getStream() << "?"; + Mangler.mangleSourceName("$RT" + llvm::utostr(ManglingNumber)); Mangler.mangle(VD, ""); } diff --git a/clang/test/CodeGenCXX/mangle-ms-back-references.cpp b/clang/test/CodeGenCXX/mangle-ms-back-references.cpp index b27a9c5acacb77..8707bff9534070 100644 --- a/clang/test/CodeGenCXX/mangle-ms-back-references.cpp +++ b/clang/test/CodeGenCXX/mangle-ms-back-references.cpp @@ -1,5 +1,18 @@ // RUN: %clang_cc1 -fms-extensions -fblocks -emit-llvm %s -o - -triple=i386-pc-win32 | FileCheck %s +namespace NS { +// The name "RT1" for the name of the class below has been specifically +// chosen to ensure that back reference lookup does not match against the +// implicitly generated "$RT1" name of the reference temporary symbol. +struct RT1 { + static const RT1& singleton; + int i; +}; +const RT1& RT1::singleton = RT1{1}; +} +// CHECK: "?$RT1@singleton@RT1@NS@@2ABU23@B" +// CHECK: "?singleton@RT1@NS@@2ABU12@B" + void f1(const char* a, const char* b) {} // CHECK: "?f1@@YAXPBD0@Z" `````````` </details> https://github.com/llvm/llvm-project/pull/85529 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
