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release/21.x: [WIP] [clang] Align cleanup structs to prevent SIGBUS on sparc32 (#152866) #154002

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@llvmbot llvmbot commented Aug 17, 2025

Backport 8071d27

Requested by: @brad0

…m#152866)

The cleanup structs expect that pointers and (u)int64_t have the same
alignment requirements, which isn't true on sparc32, which causes
SIGBUSes.

See also: llvm#66620

(cherry picked from commit 8071d27)
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llvmbot commented Aug 17, 2025

@efriedma-quic What do you think about merging this PR to the release branch?

@llvmbot llvmbot requested a review from efriedma-quic August 17, 2025 05:37
@llvmbot llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" clang:codegen IR generation bugs: mangling, exceptions, etc. labels Aug 17, 2025
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llvmbot commented Aug 17, 2025

@llvm/pr-subscribers-clang-codegen

Author: None (llvmbot)

Changes

Backport 8071d27

Requested by: @brad0


Full diff: https://github.com/llvm/llvm-project/pull/154002.diff

3 Files Affected:

  • (modified) clang/include/clang/AST/APValue.h (+1-1)
  • (modified) clang/lib/CodeGen/CodeGenFunction.h (+3-2)
  • (modified) clang/lib/CodeGen/EHScopeStack.h (+1-1)
diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
index 9999a30c51ade..cb942ea865e2d 100644
--- a/clang/include/clang/AST/APValue.h
+++ b/clang/include/clang/AST/APValue.h
@@ -143,7 +143,7 @@ class APValue {
     AddrLabelDiff
   };
 
-  class LValueBase {
+  class alignas(uint64_t) LValueBase {
     typedef llvm::PointerUnion<const ValueDecl *, const Expr *, TypeInfoLValue,
                                DynamicAllocLValue>
         PtrTy;
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 6c32c98cec011..f5ac9f387c641 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -727,7 +727,7 @@ class CodeGenFunction : public CodeGenTypeCache {
   };
 
   /// Header for data within LifetimeExtendedCleanupStack.
-  struct LifetimeExtendedCleanupHeader {
+  struct alignas(uint64_t) LifetimeExtendedCleanupHeader {
     /// The size of the following cleanup object.
     unsigned Size;
     /// The kind of cleanup to push.
@@ -949,7 +949,8 @@ class CodeGenFunction : public CodeGenTypeCache {
         LifetimeExtendedCleanupStack.size() + sizeof(Header) + Header.Size +
         (Header.IsConditional ? sizeof(ActiveFlag) : 0));
 
-    static_assert(sizeof(Header) % alignof(T) == 0,
+    static_assert((alignof(LifetimeExtendedCleanupHeader) == alignof(T)) &&
+                      (alignof(T) == alignof(RawAddress)),
                   "Cleanup will be allocated on misaligned address");
     char *Buffer = &LifetimeExtendedCleanupStack[OldSize];
     new (Buffer) LifetimeExtendedCleanupHeader(Header);
diff --git a/clang/lib/CodeGen/EHScopeStack.h b/clang/lib/CodeGen/EHScopeStack.h
index ed11dc2bb05d7..54f6ceaa52b95 100644
--- a/clang/lib/CodeGen/EHScopeStack.h
+++ b/clang/lib/CodeGen/EHScopeStack.h
@@ -143,7 +143,7 @@ class EHScopeStack {
   ///
   /// Cleanup implementations should generally be declared in an
   /// anonymous namespace.
-  class Cleanup {
+  class alignas(uint64_t) Cleanup {
     // Anchor the construction vtable.
     virtual void anchor();
 

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llvmbot commented Aug 17, 2025

@llvm/pr-subscribers-clang

Author: None (llvmbot)

Changes

Backport 8071d27

Requested by: @brad0


Full diff: https://github.com/llvm/llvm-project/pull/154002.diff

3 Files Affected:

  • (modified) clang/include/clang/AST/APValue.h (+1-1)
  • (modified) clang/lib/CodeGen/CodeGenFunction.h (+3-2)
  • (modified) clang/lib/CodeGen/EHScopeStack.h (+1-1)
diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
index 9999a30c51ade..cb942ea865e2d 100644
--- a/clang/include/clang/AST/APValue.h
+++ b/clang/include/clang/AST/APValue.h
@@ -143,7 +143,7 @@ class APValue {
     AddrLabelDiff
   };
 
-  class LValueBase {
+  class alignas(uint64_t) LValueBase {
     typedef llvm::PointerUnion<const ValueDecl *, const Expr *, TypeInfoLValue,
                                DynamicAllocLValue>
         PtrTy;
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 6c32c98cec011..f5ac9f387c641 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -727,7 +727,7 @@ class CodeGenFunction : public CodeGenTypeCache {
   };
 
   /// Header for data within LifetimeExtendedCleanupStack.
-  struct LifetimeExtendedCleanupHeader {
+  struct alignas(uint64_t) LifetimeExtendedCleanupHeader {
     /// The size of the following cleanup object.
     unsigned Size;
     /// The kind of cleanup to push.
@@ -949,7 +949,8 @@ class CodeGenFunction : public CodeGenTypeCache {
         LifetimeExtendedCleanupStack.size() + sizeof(Header) + Header.Size +
         (Header.IsConditional ? sizeof(ActiveFlag) : 0));
 
-    static_assert(sizeof(Header) % alignof(T) == 0,
+    static_assert((alignof(LifetimeExtendedCleanupHeader) == alignof(T)) &&
+                      (alignof(T) == alignof(RawAddress)),
                   "Cleanup will be allocated on misaligned address");
     char *Buffer = &LifetimeExtendedCleanupStack[OldSize];
     new (Buffer) LifetimeExtendedCleanupHeader(Header);
diff --git a/clang/lib/CodeGen/EHScopeStack.h b/clang/lib/CodeGen/EHScopeStack.h
index ed11dc2bb05d7..54f6ceaa52b95 100644
--- a/clang/lib/CodeGen/EHScopeStack.h
+++ b/clang/lib/CodeGen/EHScopeStack.h
@@ -143,7 +143,7 @@ class EHScopeStack {
   ///
   /// Cleanup implementations should generally be declared in an
   /// anonymous namespace.
-  class Cleanup {
+  class alignas(uint64_t) Cleanup {
     // Anchor the construction vtable.
     virtual void anchor();
 

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