https://github.com/pdschbrt created https://github.com/llvm/llvm-project/pull/226942
CodeGenModule::DeferredAnnotations was keyed by StringRef, but not every mangled name passed to GetOrCreateLLVMFunction outlives the call. CodeGenVTables::maybeEmitThunk mangles the thunk name into a stack-local SmallString and hands it to GetAddrOfThunk, so for an annotated virtual function the map retained a reference into a frame that was gone by the time EmitGlobalAnnotations looked the key up. ASan reports this as a stack-use-after-return in EmitGlobalAnnotations, with the freed frame being maybeEmitThunk's 'Name'. The user-visible effect is that annotations silently disappear from the this-adjusting thunks once the dead frame has been reused. Make the key own its storage, using StringMap<unsigned> as the MapVector map type so lookups still hash a StringRef without allocating. >From 4d3952b9313cec51867de92f32b354ab5c8f6eec Mon Sep 17 00:00:00 2001 From: Philipp Schubert <[email protected]> Date: Mon, 28 Sep 2026 12:04:53 +0200 Subject: [PATCH] [clang][CodeGen] Fix stack-use-after-return in deferred annotations CodeGenModule::DeferredAnnotations was keyed by StringRef, but not every mangled name passed to GetOrCreateLLVMFunction outlives the call. CodeGenVTables::maybeEmitThunk mangles the thunk name into a stack-local SmallString and hands it to GetAddrOfThunk, so for an annotated virtual function the map retained a reference into a frame that was gone by the time EmitGlobalAnnotations looked the key up. ASan reports this as a stack-use-after-return in EmitGlobalAnnotations, with the freed frame being maybeEmitThunk's 'Name'. The user-visible effect is that annotations silently disappear from the this-adjusting thunks once the dead frame has been reused. Make the key own its storage, using StringMap<unsigned> as the MapVector map type so lookups still hash a StringRef without allocating. --- clang/docs/ReleaseNotes.md | 4 ++ clang/lib/CodeGen/CodeGenModule.cpp | 4 +- clang/lib/CodeGen/CodeGenModule.h | 5 ++- clang/test/CodeGenCXX/attr-annotate-thunk.cpp | 40 +++++++++++++++++++ 4 files changed, 50 insertions(+), 3 deletions(-) create mode 100644 clang/test/CodeGenCXX/attr-annotate-thunk.cpp diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md index 3c6acf353f93f..adc941e287607 100644 --- a/clang/docs/ReleaseNotes.md +++ b/clang/docs/ReleaseNotes.md @@ -802,6 +802,10 @@ features cannot lower the translation-unit ABI level; - Fixed an assertion failure when a method or function definition follows an Objective-C `@implementation` that was ended by a nested `@interface`, `@protocol` or `@implementation` before its `@end`. (#GH209503) +- Fixed `annotate` attributes being dropped from the `this`-adjusting thunks of + annotated virtual functions. The deferred-annotation map kept a `StringRef` + into the caller's stack buffer, so the lookup at the end of the translation + unit read a dangling key. ### OpenACC Specific Changes diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 7274a8588670f..277764fa300c3 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -4863,7 +4863,7 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) { if (FD->hasAttr<AnnotateAttr>()) { StringRef MangledName = getMangledName(GD); if (GetGlobalValue(MangledName)) - DeferredAnnotations[MangledName] = FD; + DeferredAnnotations[MangledName.str()] = FD; } // Forward declarations are emitted lazily on first use. @@ -5784,7 +5784,7 @@ llvm::Constant *CodeGenModule::GetOrCreateLLVMFunction( // Store the declaration associated with this function so it is potentially // updated by further declarations or definitions and emitted at the end. if (D && D->hasAttr<AnnotateAttr>()) - DeferredAnnotations[MangledName] = cast<ValueDecl>(D); + DeferredAnnotations[MangledName.str()] = cast<ValueDecl>(D); // If we already created a function with the same mangled name (but different // type) before, take its name and add it to the list of functions to be diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h index 9e3f073c20f4a..28e9bcf9e866b 100644 --- a/clang/lib/CodeGen/CodeGenModule.h +++ b/clang/lib/CodeGen/CodeGenModule.h @@ -506,7 +506,10 @@ class CodeGenModule : public CodeGenTypeCache { // Store deferred function annotations so they can be emitted at the end with // most up to date ValueDecl that will have all the inherited annotations. - llvm::MapVector<StringRef, const ValueDecl *> DeferredAnnotations; + // The key owns its storage: not every mangled name handed to + // GetOrCreateLLVMFunction outlives the call. + llvm::MapVector<std::string, const ValueDecl *, llvm::StringMap<unsigned>> + DeferredAnnotations; /// Map used to get unique annotation strings. llvm::StringMap<llvm::Constant*> AnnotationStrings; diff --git a/clang/test/CodeGenCXX/attr-annotate-thunk.cpp b/clang/test/CodeGenCXX/attr-annotate-thunk.cpp new file mode 100644 index 0000000000000..5aa57877c1719 --- /dev/null +++ b/clang/test/CodeGenCXX/attr-annotate-thunk.cpp @@ -0,0 +1,40 @@ +// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-unknown-linux-gnu -o - | FileCheck %s + +// Annotations on a virtual function are deferred to the end of the TU, keyed +// by mangled name. For a this-adjusting thunk that name is mangled into a +// stack buffer in CodeGenVTables::maybeEmitThunk, so the deferred-annotation +// map must own a copy of the key instead of referencing the caller's storage. + +struct A { + virtual void f(); + virtual ~A(); +}; + +struct B { + virtual void g(); + virtual ~B(); +}; + +struct C : A, B { + void f() override; + __attribute__((annotate("annotated_method"))) void g() override; + __attribute__((annotate("annotated_dtor"))) ~C() override; +}; + +void C::f() {} +void C::g() {} +C::~C() {} + +// Each annotation is recorded for the function itself and for the thunk that +// adjusts `this` to the B subobject. + +// CHECK: @[[METHOD:.*]] = private unnamed_addr constant [17 x i8] c"annotated_method\00", section "llvm.metadata" +// CHECK: @[[DTOR:.*]] = private unnamed_addr constant [15 x i8] c"annotated_dtor\00", section "llvm.metadata" +// CHECK: @llvm.global.annotations = appending global [7 x { ptr, ptr, ptr, i32, ptr }] [ +// CHECK-SAME: { ptr @_ZN1C1gEv, ptr @[[METHOD]], +// CHECK-SAME: { ptr @_ZThn8_N1C1gEv, ptr @[[METHOD]], +// CHECK-SAME: { ptr @_ZN1CD2Ev, ptr @[[DTOR]], +// CHECK-SAME: { ptr @_ZN1CD1Ev, ptr @[[DTOR]], +// CHECK-SAME: { ptr @_ZThn8_N1CD1Ev, ptr @[[DTOR]], +// CHECK-SAME: { ptr @_ZN1CD0Ev, ptr @[[DTOR]], +// CHECK-SAME: { ptr @_ZThn8_N1CD0Ev, ptr @[[DTOR]], _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
