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merged 1 commit into from
Aug 26, 2025
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release/21.x: [PAC] Fix codegen for polymorphic class variables with consteval constructors (#154858) #155319

merged 1 commit into from
Aug 26, 2025

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@llvmbot llvmbot commented Aug 25, 2025

Backport e612f37

Requested by: @ahatanak

@llvmbot llvmbot added this to the LLVM 21.x Release milestone Aug 25, 2025
@github-project-automation github-project-automation bot moved this to Needs Triage in LLVM Release Status Aug 25, 2025
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llvmbot commented Aug 25, 2025

@ojhunt What do you think about merging this PR to the release branch?

@llvmbot llvmbot requested a review from ojhunt August 25, 2025 22:06
@llvmbot llvmbot added clang Clang issues not falling into any other category clang:codegen IR generation bugs: mangling, exceptions, etc. labels Aug 25, 2025
@llvmbot llvmbot mentioned this pull request Aug 25, 2025
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llvmbot commented Aug 25, 2025 •
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@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: None (llvmbot)

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Backport e612f37

Requested by: @ahatanak

Full diff: https://github.com/llvm/llvm-project/pull/155319.diff

2 Files Affected:

  • (modified) clang/lib/CodeGen/CGExprConstant.cpp (+4-3)
  • (modified) clang/test/CodeGenCXX/ptrauth-explicit-vtable-pointer-control.cpp (+29-8)
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 715bd392f59f7..0cc468ca3ab7e 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -873,8 +873,9 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
 
     for (const BaseInfo &Base : Bases) {
       bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
-      Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
-            VTableClass, Offset + Base.Offset);
+      if (!Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
+                 VTableClass, Offset + Base.Offset))
+        return false;
     }
   }
 
@@ -1620,7 +1621,7 @@ llvm::Constant *ConstantEmitter::tryEmitConstantExpr(const ConstantExpr *CE) {
   if (CE->isGLValue())
     RetType = CGM.getContext().getLValueReferenceType(RetType);
 
-  return emitAbstract(CE->getBeginLoc(), CE->getAPValueResult(), RetType);
+  return tryEmitAbstract(CE->getAPValueResult(), RetType);
 }
 
 llvm::Constant *
diff --git a/clang/test/CodeGenCXX/ptrauth-explicit-vtable-pointer-control.cpp b/clang/test/CodeGenCXX/ptrauth-explicit-vtable-pointer-control.cpp
index 1b103719fbe46..e33525c1ec0f9 100644
--- a/clang/test/CodeGenCXX/ptrauth-explicit-vtable-pointer-control.cpp
+++ b/clang/test/CodeGenCXX/ptrauth-explicit-vtable-pointer-control.cpp
@@ -1,31 +1,31 @@
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,NODISC %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-type-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,TYPE %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-address-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,ADDR %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-type-discrimination \
 // RUN:   -fptrauth-vtable-pointer-address-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,BOTH %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,NODISC %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-type-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,TYPE %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-address-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,ADDR %s
 
-// RUN: %clang_cc1 %s -x c++ -std=c++11 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
+// RUN: %clang_cc1 %s -x c++ -std=c++20 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
 // RUN:   -fptrauth-vtable-pointer-type-discrimination \
 // RUN:   -fptrauth-vtable-pointer-address-discrimination \
 // RUN:   -emit-llvm -o - | FileCheck --check-prefixes=CHECK,BOTH %s
@@ -78,6 +78,27 @@ struct authenticated(default_key, default_address_discrimination, custom_discrim
   virtual void g();
 };
 
+// CHECK: @_ZTVN5test19ConstEvalE = external unnamed_addr constant { [3 x ptr] }, align 8
+// CHECK: @_ZN5test12ceE = global %{{.*}} { ptr ptrauth (ptr getelementptr inbounds inrange(-16, 8) ({ [3 x ptr] }, ptr @_ZTVN5test19ConstEvalE, i32 0, i32 0, i32 2), i32 2, i64 0, ptr @_ZN5test12ceE) }, align 8
+// CHECK: @_ZTVN5test116ConstEvalDerivedE = linkonce_odr unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr @_ZTIN5test116ConstEvalDerivedE, ptr ptrauth (ptr @_ZN5test19ConstEval1fEv, i32 0, i64 26259, ptr getelementptr inbounds ({ [3 x ptr] }, ptr @_ZTVN5test116ConstEvalDerivedE, i32 0, i32 0, i32 2))] },{{.*}}align 8
+// CHECK: @_ZN5test13cedE = global { ptr } { ptr ptrauth (ptr getelementptr inbounds inrange(-16, 8) ({ [3 x ptr] }, ptr @_ZTVN5test116ConstEvalDerivedE, i32 0, i32 0, i32 2), i32 2, i64 0, ptr @_ZN5test13cedE) }, align 8
+
+struct authenticated(default_key, address_discrimination, no_extra_discrimination) ConstEval {
+  consteval ConstEval() {}
+  virtual void f();
+};
+
+// clang used to bail out with error message "could not emit constant value abstractly".
+ConstEval ce;
+
+struct ConstEvalDerived : public ConstEval {
+public:
+  consteval ConstEvalDerived() {}
+};
+
+// clang used to emit an undef initializer.
+ConstEvalDerived ced;
+
 template <typename T>
 struct SubClass : T {
   virtual void g();

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ojhunt commented Aug 25, 2025

@ojhunt What do you think about merging this PR to the release branch?

LGTM

@github-project-automation github-project-automation bot moved this from Needs Triage to Needs Merge in LLVM Release Status Aug 25, 2025
@tru tru merged commit 306481b into llvm:release/21.x Aug 26, 2025
@github-project-automation github-project-automation bot moved this from Needs Merge to Done in LLVM Release Status Aug 26, 2025
@ahatanak @tru
[PAC] Fix codegen for polymorphic class variables with consteval cons…
306481b 
…tructors (llvm#154858)

Fix a bug in CodeGen where such variables could cause a compilation
error or be emitted with an undef initializer when the vtable was signed
with address discrimination.

rdar://155696134
(cherry picked from commit e612f37)
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@ahatanak (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.

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No release note is needed for this fix. Clang's code generation behavior changed after this commit:

6a99326

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