[AST] Use APIntStorage to fix memory leak in EnumConstantDecl.

[topperc]

EnumConstantDecl is allocated by the ASTContext allocator so the destructor is never called.

This patch takes a similar approach to IntegerLiteral by using APIntStorage to allocate large APSInts using the ASTContext allocator as well.

The downside is that an additional heap allocation and copy of the data needs to be made when calling getInitValue if the APSInt is large.

Fixes #78160.

[llvmbot]

@llvm/pr-subscribers-clang
@llvm/pr-subscribers-clang-modules

@llvm/pr-subscribers-clang-codegen

Author: Craig Topper (topperc)

Changes

EnumConstantDecl is allocated by the ASTContext allocator so the destructor is never called.

This patch takes a similar approach to IntegerLiteral by using APIntStorage to allocate large APSInts using the ASTContext allocator as well.

The downside is that an additional heap allocation and copy of the data needs to be made when calling getInitValue if the APSInt is large.

Fixes #78160.

---

Full diff: https://github.com/llvm/llvm-project/pull/78311.diff

7 Files Affected:

• (added) clang/include/clang/AST/APNumericStorage.h (+71)
• (modified) clang/include/clang/AST/Decl.h (+14-7)
• (modified) clang/include/clang/AST/Expr.h (+1-51)
• (modified) clang/lib/AST/Decl.cpp (+9-2)
• (modified) clang/lib/CodeGen/CGBuiltin.cpp (+1-1)
• (modified) clang/lib/Sema/SemaDecl.cpp (+1-1)
• (modified) clang/lib/Serialization/ASTReaderDecl.cpp (+1-1)

diff --git a/clang/include/clang/AST/APNumericStorage.h b/clang/include/clang/AST/APNumericStorage.h
new file mode 100644
index 00000000000000..c13014b1bad4de
--- /dev/null
+++ b/clang/include/clang/AST/APNumericStorage.h
@@ -0,0 +1,71 @@
+//===--- APNumericStorage.h - Store APInt/APFloat in ASTContext -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_APNUMERICSTORAGE_H
+#define LLVM_CLANG_AST_APNUMERICSTORAGE_H
+
+#include "llvm/ADT/APFloat.h"
+#include "llvm/ADT/APInt.h"
+
+namespace clang {
+class ASTContext;
+
+/// Used by IntegerLiteral/FloatingLiteral to store the numeric without
+/// leaking memory.
+///
+/// For large floats/integers, APFloat/APInt will allocate memory from the heap
+/// to represent these numbers.  Unfortunately, when we use a BumpPtrAllocator
+/// to allocate IntegerLiteral/FloatingLiteral nodes the memory associated with
+/// the APFloat/APInt values will never get freed. APNumericStorage uses
+/// ASTContext's allocator for memory allocation.
+class APNumericStorage {
+  union {
+    uint64_t VAL;   ///< Used to store the <= 64 bits integer value.
+    uint64_t *pVal; ///< Used to store the >64 bits integer value.
+  };
+  unsigned BitWidth;
+
+  bool hasAllocation() const { return llvm::APInt::getNumWords(BitWidth) > 1; }
+
+  APNumericStorage(const APNumericStorage &) = delete;
+  void operator=(const APNumericStorage &) = delete;
+
+protected:
+  APNumericStorage() : VAL(0), BitWidth(0) {}
+
+  llvm::APInt getIntValue() const {
+    unsigned NumWords = llvm::APInt::getNumWords(BitWidth);
+    if (NumWords > 1)
+      return llvm::APInt(BitWidth, NumWords, pVal);
+    else
+      return llvm::APInt(BitWidth, VAL);
+  }
+  void setIntValue(const ASTContext &C, const llvm::APInt &Val);
+};
+
+class APIntStorage : private APNumericStorage {
+public:
+  llvm::APInt getValue() const { return getIntValue(); }
+  void setValue(const ASTContext &C, const llvm::APInt &Val) {
+    setIntValue(C, Val);
+  }
+};
+
+class APFloatStorage : private APNumericStorage {
+public:
+  llvm::APFloat getValue(const llvm::fltSemantics &Semantics) const {
+    return llvm::APFloat(Semantics, getIntValue());
+  }
+  void setValue(const ASTContext &C, const llvm::APFloat &Val) {
+    setIntValue(C, Val.bitcastToAPInt());
+  }
+};
+
+} // end namespace clang
+
+#endif // LLVM_CLANG_AST_APNUMERICSTORAGE_H
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index a807bcdd76b30d..98af552d400f3a 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -13,6 +13,7 @@
 #ifndef LLVM_CLANG_AST_DECL_H
 #define LLVM_CLANG_AST_DECL_H
 
+#include "clang/AST/APNumericStorage.h"
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTContextAllocate.h"
 #include "clang/AST/DeclAccessPair.h"
@@ -3251,15 +3252,16 @@ class FieldDecl : public DeclaratorDecl, public Mergeable<FieldDecl> {
 /// that is defined.  For example, in "enum X {a,b}", each of a/b are
 /// EnumConstantDecl's, X is an instance of EnumDecl, and the type of a/b is a
 /// TagType for the X EnumDecl.
-class EnumConstantDecl : public ValueDecl, public Mergeable<EnumConstantDecl> {
+class EnumConstantDecl : public ValueDecl,
+                         public Mergeable<EnumConstantDecl>,
+                         public APIntStorage {
   Stmt *Init; // an integer constant expression
-  llvm::APSInt Val; // The value.
+  bool IsUnsigned;
 
 protected:
-  EnumConstantDecl(DeclContext *DC, SourceLocation L,
+  EnumConstantDecl(const ASTContext &C, DeclContext *DC, SourceLocation L,
                    IdentifierInfo *Id, QualType T, Expr *E,
-                   const llvm::APSInt &V)
-    : ValueDecl(EnumConstant, DC, L, Id, T), Init((Stmt*)E), Val(V) {}
+                   const llvm::APSInt &V);
 
 public:
   friend class StmtIteratorBase;
@@ -3272,10 +3274,15 @@ class EnumConstantDecl : public ValueDecl, public Mergeable<EnumConstantDecl> {
 
   const Expr *getInitExpr() const { return (const Expr*) Init; }
   Expr *getInitExpr() { return (Expr*) Init; }
-  const llvm::APSInt &getInitVal() const { return Val; }
+  llvm::APSInt getInitVal() const {
+    return llvm::APSInt(getValue(), IsUnsigned);
+  }
 
   void setInitExpr(Expr *E) { Init = (Stmt*) E; }
-  void setInitVal(const llvm::APSInt &V) { Val = V; }
+  void setInitVal(const ASTContext &C, const llvm::APSInt &V) {
+    setValue(C, V);
+    IsUnsigned = V.isUnsigned();
+  }
 
   SourceRange getSourceRange() const override LLVM_READONLY;
 
diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
index a41f2d66b37b69..53e4544888ff66 100644
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -13,6 +13,7 @@
 #ifndef LLVM_CLANG_AST_EXPR_H
 #define LLVM_CLANG_AST_EXPR_H
 
+#include "clang/AST/APNumericStorage.h"
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTVector.h"
 #include "clang/AST/ComputeDependence.h"
@@ -1479,57 +1480,6 @@ class DeclRefExpr final
   }
 };
 
-/// Used by IntegerLiteral/FloatingLiteral to store the numeric without
-/// leaking memory.
-///
-/// For large floats/integers, APFloat/APInt will allocate memory from the heap
-/// to represent these numbers.  Unfortunately, when we use a BumpPtrAllocator
-/// to allocate IntegerLiteral/FloatingLiteral nodes the memory associated with
-/// the APFloat/APInt values will never get freed. APNumericStorage uses
-/// ASTContext's allocator for memory allocation.
-class APNumericStorage {
-  union {
-    uint64_t VAL;    ///< Used to store the <= 64 bits integer value.
-    uint64_t *pVal;  ///< Used to store the >64 bits integer value.
-  };
-  unsigned BitWidth;
-
-  bool hasAllocation() const { return llvm::APInt::getNumWords(BitWidth) > 1; }
-
-  APNumericStorage(const APNumericStorage &) = delete;
-  void operator=(const APNumericStorage &) = delete;
-
-protected:
-  APNumericStorage() : VAL(0), BitWidth(0) { }
-
-  llvm::APInt getIntValue() const {
-    unsigned NumWords = llvm::APInt::getNumWords(BitWidth);
-    if (NumWords > 1)
-      return llvm::APInt(BitWidth, NumWords, pVal);
-    else
-      return llvm::APInt(BitWidth, VAL);
-  }
-  void setIntValue(const ASTContext &C, const llvm::APInt &Val);
-};
-
-class APIntStorage : private APNumericStorage {
-public:
-  llvm::APInt getValue() const { return getIntValue(); }
-  void setValue(const ASTContext &C, const llvm::APInt &Val) {
-    setIntValue(C, Val);
-  }
-};
-
-class APFloatStorage : private APNumericStorage {
-public:
-  llvm::APFloat getValue(const llvm::fltSemantics &Semantics) const {
-    return llvm::APFloat(Semantics, getIntValue());
-  }
-  void setValue(const ASTContext &C, const llvm::APFloat &Val) {
-    setIntValue(C, Val.bitcastToAPInt());
-  }
-};
-
 class IntegerLiteral : public Expr, public APIntStorage {
   SourceLocation Loc;
 
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index e1440e5183a4e6..d373329d7272a4 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -5369,16 +5369,23 @@ void CapturedDecl::setBody(Stmt *B) { BodyAndNothrow.setPointer(B); }
 bool CapturedDecl::isNothrow() const { return BodyAndNothrow.getInt(); }
 void CapturedDecl::setNothrow(bool Nothrow) { BodyAndNothrow.setInt(Nothrow); }
 
+EnumConstantDecl::EnumConstantDecl(const ASTContext &C, DeclContext *DC,
+                                   SourceLocation L, IdentifierInfo *Id,
+                                   QualType T, Expr *E, const llvm::APSInt &V)
+    : ValueDecl(EnumConstant, DC, L, Id, T), Init((Stmt *)E) {
+  setInitVal(C, V);
+}
+
 EnumConstantDecl *EnumConstantDecl::Create(ASTContext &C, EnumDecl *CD,
                                            SourceLocation L,
                                            IdentifierInfo *Id, QualType T,
                                            Expr *E, const llvm::APSInt &V) {
-  return new (C, CD) EnumConstantDecl(CD, L, Id, T, E, V);
+  return new (C, CD) EnumConstantDecl(C, CD, L, Id, T, E, V);
 }
 
 EnumConstantDecl *
 EnumConstantDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
-  return new (C, ID) EnumConstantDecl(nullptr, SourceLocation(), nullptr,
+  return new (C, ID) EnumConstantDecl(C, nullptr, SourceLocation(), nullptr,
                                       QualType(), nullptr, llvm::APSInt());
 }
 
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 1ed35befe1361f..ee6866dabaa89b 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -13047,7 +13047,7 @@ Value *CodeGenFunction::EmitBPFBuiltinExpr(unsigned BuiltinID,
     const auto *DR = cast<DeclRefExpr>(CE->getSubExpr());
     const auto *Enumerator = cast<EnumConstantDecl>(DR->getDecl());
 
-    auto &InitVal = Enumerator->getInitVal();
+    auto InitVal = Enumerator->getInitVal();
     std::string InitValStr;
     if (InitVal.isNegative() || InitVal > uint64_t(INT64_MAX))
       InitValStr = std::to_string(InitVal.getSExtValue());
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 722e2ac9e4ff8d..793bb90da74d28 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -20214,7 +20214,7 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
     // Adjust the APSInt value.
     InitVal = InitVal.extOrTrunc(NewWidth);
     InitVal.setIsSigned(NewSign);
-    ECD->setInitVal(InitVal);
+    ECD->setInitVal(Context, InitVal);
 
     // Adjust the Expr initializer and type.
     if (ECD->getInitExpr() &&
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 547eb77930b4ee..b05efe4f76517e 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -910,7 +910,7 @@ void ASTDeclReader::VisitEnumConstantDecl(EnumConstantDecl *ECD) {
   VisitValueDecl(ECD);
   if (Record.readInt())
     ECD->setInitExpr(Record.readExpr());
-  ECD->setInitVal(Record.readAPSInt());
+  ECD->setInitVal(Reader.getContext(), Record.readAPSInt());
   mergeMergeable(ECD);
 }
 

[AaronBallman]

LGTM thank you for the fix! I'm on the fence about this getting a release note, but leaning towards mentioning it as fixing a memory leak (I don't expect this to be observable for most folks because cleaning up the ASTContext generally means quitting the process but it would be observable for folks using Clang as a library).