[LifetimeSafety] Implement support for lifetimebound attribute

clang/include/clang/Analysis/Analyses/LifetimeAnnotations.h

@@ -0,0 +1,44 @@
+//===- LifetimeAnnotations.h -  -*--------------- 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
+//
+//===----------------------------------------------------------------------===//
+// Helper functions to inspect and infer lifetime annotations.
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMEANNOTATIONS_H
+#define LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMEANNOTATIONS_H
+
+#include "clang/AST/DeclCXX.h"
+
+namespace clang {
+namespace lifetimes {
+
+/// Returns the most recent declaration of the method to ensure all
+/// lifetime-bound attributes from redeclarations are considered.
+const FunctionDecl *getDeclWithMergedLifetimeBoundAttrs(const FunctionDecl *FD);
+
+/// Returns the most recent declaration of the method to ensure all
+/// lifetime-bound attributes from redeclarations are considered.
+const CXXMethodDecl *
+getDeclWithMergedLifetimeBoundAttrs(const CXXMethodDecl *CMD);
+
+// Return true if this is an "normal" assignment operator.
+// We assume that a normal assignment operator always returns *this, that is,
+// an lvalue reference that is the same type as the implicit object parameter
+// (or the LHS for a non-member operator==).
+bool isNormalAssignmentOperator(const FunctionDecl *FD);
+
+/// Returns true if this is an assignment operator where the parameter
+/// has the lifetimebound attribute.
+bool isAssignmentOperatorLifetimeBound(const CXXMethodDecl *CMD);
+
+/// Returns true if the implicit object parameter (this) should be considered
+/// lifetimebound, either due to an explicit lifetimebound attribute on the
+/// method or because it's a normal assignment operator.
+bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD);
+} // namespace lifetimes
+} // namespace clang
+
+#endif // LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMEANNOTATIONS_H

clang/include/clang/Analysis/Analyses/LifetimeSafety.h

@@ -75,13 +75,14 @@ template <typename Tag> struct ID {
   }
 };
 
-template <typename Tag>
-inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, ID<Tag> ID) {
-  return OS << ID.Value;
-}
-
 using LoanID = ID<struct LoanTag>;
 using OriginID = ID<struct OriginTag>;
+inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, LoanID ID) {
+  return OS << ID.Value;
+}
+inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, OriginID ID) {
+  return OS << ID.Value;
+}
 
 // Using LLVM's immutable collections is efficient for dataflow analysis
 // as it avoids deep copies during state transitions.

clang/lib/Analysis/CMakeLists.txt

@@ -21,6 +21,7 @@ add_clang_library(clangAnalysis
   FixitUtil.cpp
   IntervalPartition.cpp
   IssueHash.cpp
+  LifetimeAnnotations.cpp
   LifetimeSafety.cpp
   LiveVariables.cpp
   MacroExpansionContext.cpp

clang/lib/Analysis/LifetimeAnnotations.cpp

@@ -0,0 +1,75 @@
+//===- LifetimeAnnotations.cpp -  -*--------------- 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
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Analysis/Analyses/LifetimeAnnotations.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Attr.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/Type.h"
+#include "clang/AST/TypeLoc.h"
+
+namespace clang {
+namespace lifetimes {
+
+const FunctionDecl *
+getDeclWithMergedLifetimeBoundAttrs(const FunctionDecl *FD) {
+  return FD != nullptr ? FD->getMostRecentDecl() : nullptr;
+}
+
+const CXXMethodDecl *
+getDeclWithMergedLifetimeBoundAttrs(const CXXMethodDecl *CMD) {
+  const FunctionDecl *FD = CMD;
+  return cast_if_present<CXXMethodDecl>(
+      getDeclWithMergedLifetimeBoundAttrs(FD));
+}
+
+bool isNormalAssignmentOperator(const FunctionDecl *FD) {
+  OverloadedOperatorKind OO = FD->getDeclName().getCXXOverloadedOperator();
+  bool IsAssignment = OO == OO_Equal || isCompoundAssignmentOperator(OO);
+  if (!IsAssignment)
+    return false;
+  QualType RetT = FD->getReturnType();
+  if (!RetT->isLValueReferenceType())
+    return false;
+  ASTContext &Ctx = FD->getASTContext();
+  QualType LHST;
+  auto *MD = dyn_cast<CXXMethodDecl>(FD);
+  if (MD && MD->isCXXInstanceMember())
+    LHST = Ctx.getLValueReferenceType(MD->getFunctionObjectParameterType());
+  else
+    LHST = FD->getParamDecl(0)->getType();
+  return Ctx.hasSameType(RetT, LHST);
+}
+
+bool isAssignmentOperatorLifetimeBound(const CXXMethodDecl *CMD) {
+  CMD = getDeclWithMergedLifetimeBoundAttrs(CMD);
+  return CMD && isNormalAssignmentOperator(CMD) && CMD->param_size() == 1 &&
+         CMD->getParamDecl(0)->hasAttr<clang::LifetimeBoundAttr>();
+}
+
+bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
+  FD = getDeclWithMergedLifetimeBoundAttrs(FD);
+  const TypeSourceInfo *TSI = FD->getTypeSourceInfo();
+  if (!TSI)
+    return false;
+  // Don't declare this variable in the second operand of the for-statement;
+  // GCC miscompiles that by ending its lifetime before evaluating the
+  // third operand. See gcc.gnu.org/PR86769.
+  AttributedTypeLoc ATL;
+  for (TypeLoc TL = TSI->getTypeLoc();
+       (ATL = TL.getAsAdjusted<AttributedTypeLoc>());
+       TL = ATL.getModifiedLoc()) {
+    if (ATL.getAttrAs<clang::LifetimeBoundAttr>())
+      return true;
+  }
+
+  return isNormalAssignmentOperator(FD);
+}
+
+} // namespace lifetimes
+} // namespace clang