C++: Output destructors of temporary objects

Author: jketema

cpp/ql/lib/semmle/code/cpp/exprs/Expr.qll

@@ -1322,3 +1322,23 @@ class CoYieldExpr extends UnaryOperation, @co_yield {
 
   override int getPrecedence() { result = 2 }
 }
+
+class ReuseExpr extends Expr, @reuseexpr {
+  override string getAPrimaryQlClass() { result = "ReuseExpr" }
+
+  override string toString() {
+    result = "reuse of " + this.getReusedExpr().toString()
+  }
+
+  override Type getType() {
+    result = this.getReusedExpr().getType()
+  }
+
+  override string getValueCategoryString() {
+    result = this.getReusedExpr().getValueCategoryString()
+  }
+
+  Expr getReusedExpr() {
+    expr_reuse(underlyingElement(this), unresolveElement(result))
+  }
+}

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -1513,6 +1513,11 @@ exprs(
     int location: @location_expr ref
 );
 
+expr_reuse(
+    int reuse: @expr ref,
+    int original: @expr ref
+)
+
 /*
   case @value.category of
     1 = prval
@@ -1741,6 +1746,7 @@ case @expr.kind of
 | 360 = @isunsigned
 | 361 = @isvoid
 | 362 = @isvolatile
+| 363 = @reuseexpr
 ;
 
 @var_args_expr = @vastartexpr

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

@@ -0,0 +1,24 @@
+class ClassWithDestructor2 {
+public:
+    ClassWithDestructor2();
+    ~ClassWithDestructor2();
+
+    char get_x();
+};
+
+class ClassWithConstructor {
+public:
+    ClassWithConstructor(char x, char y);
+};
+
+char temp_test() {
+    char x = ClassWithDestructor2().get_x();
+    ClassWithConstructor y('a', ClassWithDestructor2().get_x());
+    return ClassWithDestructor2().get_x();
+}
+
+
+char temp_test2() {
+    new ClassWithDestructor2();
+    return ClassWithDestructor2().get_x() + ClassWithDestructor2().get_x();
+}