Merge pull request #15735 from MathiasVP/ir-for-vacuous-destructor-calls

C++: IR construction for `VacuousDestructorCall`s

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll

@@ -2359,6 +2359,47 @@ class TranslatedDestructorFieldDestruction extends TranslatedNonConstantExpr, St
   private TranslatedExpr getDestructorCall() { result = getTranslatedExpr(expr.getExpr()) }
 }
 
+/**
+ * The IR translation of a vacuous destructor call. That is, an expression that
+ * looks like a destructor call, but has no effect.
+ *
+ * Note that, even though there's no destructor call, we should still evaluate
+ * the qualifier.
+ */
+class TranslatedVacuousDestructorCall extends TranslatedNonConstantExpr {
+  override VacuousDestructorCall expr;
+
+  override Instruction getInstructionSuccessorInternal(InstructionTag tag, EdgeKind kind) { none() }
+
+  final TranslatedExpr getQualifier() {
+    result = getTranslatedExpr(expr.getQualifier().getFullyConverted())
+  }
+
+  override Instruction getFirstInstruction(EdgeKind kind) {
+    result = this.getQualifier().getFirstInstruction(kind)
+  }
+
+  override Instruction getChildSuccessorInternal(TranslatedElement child, EdgeKind kind) {
+    child = this.getQualifier() and
+    result = this.getParent().getChildSuccessor(this, kind)
+  }
+
+  override TranslatedElement getChildInternal(int id) {
+    id = 0 and
+    result = this.getQualifier()
+  }
+
+  override Instruction getResult() { none() }
+
+  override predicate hasInstruction(Opcode opcode, InstructionTag tag, CppType resultType) {
+    none()
+  }
+
+  override Instruction getALastInstructionInternal() {
+    result = this.getQualifier().getALastInstruction()
+  }
+}
+
 /**
  * The IR translation of the `?:` operator. This class has the portions of the implementation that
  * are shared between the standard three-operand form (`a ? b : c`) and the GCC-extension

cpp/ql/test/library-tests/ir/ir/PrintAST.expected

@@ -2189,6 +2189,26 @@ void static_variable_with_destructor_3() {
 
 static ClassWithDestructor global_class_with_destructor;
 
+namespace vacuous_destructor_call {
+    template<typename T>
+    T& get(T& t) { return t; }
+
+    template<typename T>
+    void call_destructor(T& t) {
+        get(t).~T();
+    }
+
+    void non_vacuous_destructor_call() {
+        ClassWithDestructor c;
+        call_destructor(c);
+    }
+
+    void vacuous_destructor_call() {
+        int i;
+        call_destructor(i);
+    }
+}
+
 void TryCatchDestructors(bool b) {
   try {
     String s;

cpp/ql/test/library-tests/ir/ir/aliased_ir.expected

@@ -7,7 +7,6 @@ missingOperandType
 duplicateChiOperand
 sideEffectWithoutPrimary
 instructionWithoutSuccessor
-| VacuousDestructorCall.cpp:2:29:2:29 | InitializeIndirection: y | Instruction 'InitializeIndirection: y' has no successors in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
 | ms_try_mix.cpp:35:13:35:19 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:29:6:29:19 | void ms_finally_mix(int) | void ms_finally_mix(int) |
 | ms_try_mix.cpp:53:5:53:11 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:49:6:49:28 | void ms_empty_finally_at_end() | void ms_empty_finally_at_end() |
 | statements.cpp:25:5:25:9 | ReThrow: re-throw exception  | Instruction 'ReThrow: re-throw exception ' has no successors in function '$@'. | statements.cpp:21:6:21:16 | void early_throw(int) | void early_throw(int) |

cpp/ql/test/library-tests/ir/ir/ir.cpp

@@ -8,9 +8,6 @@ missingOperandType
 duplicateChiOperand
 sideEffectWithoutPrimary
 instructionWithoutSuccessor
-| VacuousDestructorCall.cpp:2:29:2:29 | InitializeIndirection: y | Instruction 'InitializeIndirection: y' has no successors in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
-| VacuousDestructorCall.cpp:3:3:3:3 | VariableAddress: x | Instruction 'VariableAddress: x' has no successors in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
-| VacuousDestructorCall.cpp:4:3:4:3 | Load: y | Instruction 'Load: y' has no successors in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
 | ms_try_mix.cpp:35:13:35:19 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:29:6:29:19 | void ms_finally_mix(int) | void ms_finally_mix(int) |
 | ms_try_mix.cpp:53:5:53:11 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:49:6:49:28 | void ms_empty_finally_at_end() | void ms_empty_finally_at_end() |
 | statements.cpp:25:5:25:9 | ReThrow: re-throw exception  | Instruction 'ReThrow: re-throw exception ' has no successors in function '$@'. | statements.cpp:21:6:21:16 | void early_throw(int) | void early_throw(int) |
@@ -33,7 +30,6 @@ multipleIRTypes
 lostReachability
 backEdgeCountMismatch
 useNotDominatedByDefinition
-| VacuousDestructorCall.cpp:2:29:2:29 | Address | Operand 'Address' is not dominated by its definition in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
 | ms_try_except.cpp:9:19:9:19 | Left | Operand 'Left' is not dominated by its definition in function '$@'. | ms_try_except.cpp:2:6:2:18 | void ms_try_except(int) | void ms_try_except(int) |
 | ms_try_except.cpp:9:19:9:19 | Left | Operand 'Left' is not dominated by its definition in function '$@'. | ms_try_except.cpp:2:6:2:18 | void ms_try_except(int) | void ms_try_except(int) |
 | ms_try_except.cpp:19:17:19:21 | Left | Operand 'Left' is not dominated by its definition in function '$@'. | ms_try_except.cpp:2:6:2:18 | void ms_try_except(int) | void ms_try_except(int) |

cpp/ql/test/library-tests/ir/ir/operand_locations.expected

@@ -7,7 +7,6 @@ missingOperandType
 duplicateChiOperand
 sideEffectWithoutPrimary
 instructionWithoutSuccessor
-| VacuousDestructorCall.cpp:2:29:2:29 | InitializeIndirection: y | Instruction 'InitializeIndirection: y' has no successors in function '$@'. | VacuousDestructorCall.cpp:2:6:2:6 | void CallDestructor<int>(int, int*) | void CallDestructor<int>(int, int*) |
 | ms_try_mix.cpp:35:13:35:19 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:29:6:29:19 | void ms_finally_mix(int) | void ms_finally_mix(int) |
 | ms_try_mix.cpp:53:5:53:11 | ThrowValue: throw ... | Instruction 'ThrowValue: throw ...' has no successors in function '$@'. | ms_try_mix.cpp:49:6:49:28 | void ms_empty_finally_at_end() | void ms_empty_finally_at_end() |
 | statements.cpp:25:5:25:9 | ReThrow: re-throw exception  | Instruction 'ReThrow: re-throw exception ' has no successors in function '$@'. | statements.cpp:21:6:21:16 | void early_throw(int) | void early_throw(int) |