[PATCH] D129097: [clang][dataflow] Handle null pointers of type std::nullptr_t

[Eric Li via Phabricator via cfe-commits]

li.zhe.hua created this revision.
li.zhe.hua added a reviewer: gribozavr2.
Herald added subscribers: martong, tschuett, xazax.hun.
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li.zhe.hua requested review of this revision.
Herald added a project: clang.
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Treat `std::nullptr_t` as a regular scalar type to avoid tripping
assertions when analyzing code that uses `std::nullptr_t`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129097

Files:
  clang/include/clang/Analysis/FlowSensitive/DataflowAnalysisContext.h
  clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
  clang/unittests/Analysis/FlowSensitive/TransferTest.cpp


Index: clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
===================================================================
--- clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
+++ clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
@@ -2219,6 +2219,9 @@
       int *FooY = nullptr;
       bool **Bar = nullptr;
       Baz *Baz = nullptr;
+      // Use decltype to avoid needing to include <cstddef>. This generates an
+      // implicit NullToPointer cast of type `std::nullptr_t`.
+      decltype(nullptr) Null = 0;
       // [[p]]
     }
   )";
@@ -2242,6 +2245,9 @@
                 const ValueDecl *BazDecl = findValueDecl(ASTCtx, "Baz");
                 ASSERT_THAT(BazDecl, NotNull());
 
+                const ValueDecl *NullDecl = findValueDecl(ASTCtx, "Null");
+                ASSERT_THAT(NullDecl, NotNull());
+
                 const auto *FooXVal =
                     cast<PointerValue>(Env.getValue(*FooXDecl, SkipPast::None));
                 const auto *FooYVal =
@@ -2250,6 +2256,8 @@
                     cast<PointerValue>(Env.getValue(*BarDecl, SkipPast::None));
                 const auto *BazVal =
                     cast<PointerValue>(Env.getValue(*BazDecl, SkipPast::None));
+                const auto *NullVal =
+                    cast<PointerValue>(Env.getValue(*NullDecl, SkipPast::None));
 
                 EXPECT_EQ(FooXVal, FooYVal);
                 EXPECT_NE(FooXVal, BarVal);
@@ -2267,6 +2275,11 @@
                 const StorageLocation &BazPointeeLoc = BazVal->getPointeeLoc();
                 EXPECT_TRUE(isa<AggregateStorageLocation>(BazPointeeLoc));
                 EXPECT_THAT(Env.getValue(BazPointeeLoc), IsNull());
+
+                const StorageLocation &NullPointeeLoc =
+                    NullVal->getPointeeLoc();
+                EXPECT_TRUE(isa<ScalarStorageLocation>(NullPointeeLoc));
+                EXPECT_THAT(Env.getValue(NullPointeeLoc), IsNull());
               });
 }
 
Index: clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
===================================================================
--- clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
+++ clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
@@ -24,8 +24,8 @@
 
 StorageLocation &
 DataflowAnalysisContext::getStableStorageLocation(QualType Type) {
-  assert(!Type.isNull());
-  if (Type->isStructureOrClassType() || Type->isUnionType()) {
+  if (!Type.isNull() &&
+      (Type->isStructureOrClassType() || Type->isUnionType())) {
     // FIXME: Explore options to avoid eager initialization of fields as some of
     // them might not be needed for a particular analysis.
     llvm::DenseMap<const ValueDecl *, StorageLocation *> FieldLocs;
@@ -57,8 +57,8 @@
 
 PointerValue &
 DataflowAnalysisContext::getOrCreateNullPointerValue(QualType PointeeType) {
-  assert(!PointeeType.isNull());
-  auto CanonicalPointeeType = PointeeType.getCanonicalType();
+  auto CanonicalPointeeType =
+      PointeeType.isNull() ? PointeeType : PointeeType.getCanonicalType();
   auto Res = NullPointerVals.try_emplace(CanonicalPointeeType, nullptr);
   if (Res.second) {
     auto &PointeeLoc = getStableStorageLocation(CanonicalPointeeType);
Index: clang/include/clang/Analysis/FlowSensitive/DataflowAnalysisContext.h
===================================================================
--- clang/include/clang/Analysis/FlowSensitive/DataflowAnalysisContext.h
+++ clang/include/clang/Analysis/FlowSensitive/DataflowAnalysisContext.h
@@ -251,6 +251,17 @@
   bool equivalentBoolValues(BoolValue &Val1, BoolValue &Val2);
 
 private:
+  struct NullableQualTypeDenseMapInfo : private llvm::DenseMapInfo<QualType> {
+    static QualType getEmptyKey() {
+      // Allow a NULL `QualType` by using a different value as the empty key.
+      return QualType::getFromOpaquePtr(reinterpret_cast<Type *>(1));
+    }
+
+    using DenseMapInfo::getHashValue;
+    using DenseMapInfo::getTombstoneKey;
+    using DenseMapInfo::isEqual;
+  };
+
   /// Adds all constraints of the flow condition identified by `Token` and all
   /// of its transitive dependencies to `Constraints`. `VisitedTokens` is used
   /// to track tokens of flow conditions that were already visited by recursive
@@ -311,7 +322,8 @@
   // required to initialize the `PointeeLoc` field in `PointerValue`. Consider
   // creating a type-independent `NullPointerValue` without a `PointeeLoc`
   // field.
-  llvm::DenseMap<QualType, PointerValue *> NullPointerVals;
+  llvm::DenseMap<QualType, PointerValue *, NullableQualTypeDenseMapInfo>
+      NullPointerVals;
 
   AtomicBoolValue &TrueVal;
   AtomicBoolValue &FalseVal;

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