[CFG] [analyzer] Work around a disappearing CXXBindTemporaryExpr.

Sometimes template instantiation causes CXXBindTemporaryExpr to be missing in
its usual spot. In CFG, temporary destructors work by relying on
CXXBindTemporaryExprs, so they won't work in this case.

Avoid the crash and notify the clients that we've encountered an unsupported AST
by failing to provide the ill-formed construction context for the temporary.

Differential Revision: https://reviews.llvm.org/D44955

llvm-svn: 328895

diff --git a/clang/include/clang/Analysis/ConstructionContext.h b/clang/include/clang/Analysis/ConstructionContext.h
index 91d11fe..8df95a8 100644 (file)
--- a/clang/include/clang/Analysis/ConstructionContext.h
+++ b/clang/include/clang/Analysis/ConstructionContext.h
@@ -131,7 +131,8 @@ private:
 
 public:
   /// Consume the construction context layer, together with its parent layers,
-  /// and wrap it up into a complete construction context.
+  /// and wrap it up into a complete construction context. May return null
+  /// if layers do not form any supported construction context.
   static const ConstructionContext *
   createFromLayers(BumpVectorContext &C,
                    const ConstructionContextLayer *TopLayer);

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 0f05561..34d4016 100644 (file)
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -736,12 +736,12 @@ private:
     if (BuildOpts.AddRichCXXConstructors) {
       if (const ConstructionContextLayer *Layer =
               ConstructionContextMap.lookup(CE)) {
-        const ConstructionContext *CC =
-            ConstructionContext::createFromLayers(cfg->getBumpVectorContext(),
-                                                  Layer);
-        B->appendConstructor(CE, CC, cfg->getBumpVectorContext());
         cleanupConstructionContext(CE);
-        return;
+        if (const auto *CC = ConstructionContext::createFromLayers(
+                cfg->getBumpVectorContext(), Layer)) {
+          B->appendConstructor(CE, CC, cfg->getBumpVectorContext());
+          return;
+        }
       }
     }
 
@@ -757,12 +757,12 @@ private:
       if (CFGCXXRecordTypedCall::isCXXRecordTypedCall(CE, *Context)) {
         if (const ConstructionContextLayer *Layer =
                 ConstructionContextMap.lookup(CE)) {
-          const ConstructionContext *CC =
-              ConstructionContext::createFromLayers(cfg->getBumpVectorContext(),
-                                                    Layer);
-          B->appendCXXRecordTypedCall(CE, CC, cfg->getBumpVectorContext());
           cleanupConstructionContext(CE);
-          return;
+          if (const auto *CC = ConstructionContext::createFromLayers(
+                  cfg->getBumpVectorContext(), Layer)) {
+            B->appendCXXRecordTypedCall(CE, CC, cfg->getBumpVectorContext());
+            return;
+          }
         }
       }
     }

diff --git a/clang/lib/Analysis/ConstructionContext.cpp b/clang/lib/Analysis/ConstructionContext.cpp
index ad0dbd2..9f3c00b 100644 (file)
--- a/clang/lib/Analysis/ConstructionContext.cpp
+++ b/clang/lib/Analysis/ConstructionContext.cpp
@@ -101,9 +101,12 @@ const ConstructionContext *ConstructionContext::createFromLayers(
     if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(S)) {
       // If the object requires destruction and is not lifetime-extended,
       // then it must have a BTE within its MTE.
-      assert(MTE->getType().getCanonicalType()
+      // FIXME: This should be an assertion.
+      if (!(MTE->getType().getCanonicalType()
                 ->getAsCXXRecordDecl()->hasTrivialDestructor() ||
-             MTE->getStorageDuration() != SD_FullExpression);
+             MTE->getStorageDuration() != SD_FullExpression))
+        return nullptr;
+
       assert(TopLayer->isLast());
       return create<TemporaryObjectConstructionContext>(C, nullptr, MTE);
     }

diff --git a/clang/test/Analysis/missing-bind-temporary.cpp b/clang/test/Analysis/missing-bind-temporary.cpp
new file mode 100644 (file)
index 0000000..efa608b
--- /dev/null
+++ b/clang/test/Analysis/missing-bind-temporary.cpp
@@ -0,0 +1,130 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=debug.DumpCFG %s > %t 2>&1
+// RUN: FileCheck --input-file=%t %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -std=c++14 -verify %s
+
+void clang_analyzer_eval(bool);
+
+int global;
+
+namespace variant_0 {
+// This variant of the code works correctly. Function foo() is not a template
+// function. Note that there are two destructors within foo().
+
+class A {
+public:
+  ~A() { ++global; }
+};
+
+class B {
+  A a;
+};
+
+// CHECK: void foo(int)
+// CHECK:       [B1]
+// CHECK-NEXT:    1:  (CXXConstructExpr, [B1.2], class variant_0::B)
+// CHECK-NEXT:    2: variant_0::B i;
+// CHECK-NEXT:    3: operator=
+// CHECK-NEXT:    4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, class variant_0::B &(*)(class variant_0::B &&) noexcept)
+// CHECK-NEXT:    5: i
+// CHECK-NEXT:    6: {} (CXXConstructExpr, [B1.7], [B1.8], class variant_0::B)
+// CHECK-NEXT:    7: [B1.6] (BindTemporary)
+// CHECK-NEXT:    8: [B1.7]
+// CHECK-NEXT:    9: [B1.5] = [B1.8] (OperatorCall)
+// CHECK-NEXT:   10: ~variant_0::B() (Temporary object destructor)
+// CHECK-NEXT:   11: [B1.2].~B() (Implicit destructor)
+void foo(int) {
+  B i;
+  i = {};
+}
+
+void bar() {
+  global = 0;
+  foo(1);
+  clang_analyzer_eval(global == 2); // expected-warning{{TRUE}}
+}
+
+} // end namespace variant_0
+
+namespace variant_1 {
+// Suddenly, if we turn foo() into a template, we are missing a
+// CXXBindTemporaryExpr in the AST, and therefore we're missing a
+// temporary destructor in the CFG.
+
+class A {
+public:
+  ~A() { ++global; }
+};
+
+class B {
+  A a;
+};
+
+// FIXME: Find the construction context for {} and enforce the temporary
+// destructor.
+// CHECK: template<> void foo<int>(int)
+// CHECK:       [B1]
+// CHECK-NEXT:    1:  (CXXConstructExpr, [B1.2], class variant_1::B)
+// CHECK-NEXT:    2: variant_1::B i;
+// CHECK-NEXT:    3: operator=
+// CHECK-NEXT:    4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, class variant_1::B &(*)(class variant_1::B &&) noexcept)
+// CHECK-NEXT:    5: i
+// CHECK-NEXT:    6: {} (CXXConstructExpr, class variant_1::B)
+// CHECK-NEXT:    7: [B1.6]
+// CHECK-NEXT:    8: [B1.5] = [B1.7] (OperatorCall)
+// CHECK-NEXT:    9: [B1.2].~B() (Implicit destructor)
+template <typename T> void foo(T) {
+  B i;
+  i = {};
+}
+
+void bar() {
+  global = 0;
+  foo(1);
+  // FIXME: Should be TRUE, i.e. we should call (and inline) two destructors.
+  clang_analyzer_eval(global == 2); // expected-warning{{UNKNOWN}}
+}
+
+} // end namespace variant_1
+
+namespace variant_2 {
+// Making field 'a' in class 'B' public turns the class into an aggregate.
+// In this case there is no constructor at {} - only an aggregate
+// initialization. Aggregate initialization is unsupported for now.
+
+class A {
+public:
+  ~A() { ++global; }
+};
+
+class B {
+public:
+  A a;
+};
+
+// CHECK: template<> void foo<int>(int)
+// CHECK:       [B1]
+// CHECK-NEXT:    1:  (CXXConstructExpr, [B1.2], class variant_2::B)
+// CHECK-NEXT:    2: variant_2::B i;
+// CHECK-NEXT:    3: operator=
+// CHECK-NEXT:    4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, class variant_2::B &(*)(class variant_2::B &&) noexcept)
+// CHECK-NEXT:    5: i
+// CHECK-NEXT:    6: {}
+// CHECK-NEXT:    7: {}
+// CHECK-NEXT:    8: [B1.7] (BindTemporary)
+// CHECK-NEXT:    9: [B1.8]
+// CHECK-NEXT:   10: [B1.5] = [B1.9] (OperatorCall)
+// CHECK-NEXT:   11: ~variant_2::B() (Temporary object destructor)
+// CHECK-NEXT:   12: [B1.2].~B() (Implicit destructor)
+template <typename T> void foo(T) {
+  B i;
+  i = {};
+}
+
+void bar() {
+  global = 0;
+  foo(1);
+  // FIXME: Should be TRUE, i.e. we should call (and inline) two destructors.
+  clang_analyzer_eval(global == 2); // expected-warning{{UNKNOWN}}
+}
+
+} // end namespace variant_2