Merge pull request github#15318 from rdmarsh2/rdmarsh2/cpp/first-class-destructors

C++: First-class destructors in AST

Author: Robert Marsh

cpp/ql/lib/semmle/code/cpp/PrintAST.qll

@@ -306,7 +306,14 @@ class ExprNode extends AstNode {
 
   ExprNode() { expr = ast }
 
-  override AstNode getChildInternal(int childIndex) { result.getAst() = expr.getChild(childIndex) }
+  override AstNode getChildInternal(int childIndex) {
+    result.getAst() = expr.getChild(childIndex)
+    or
+    exists(int destructorIndex |
+      result.getAst() = expr.getImplicitDestructorCall(destructorIndex) and
+      childIndex = destructorIndex + max(int index | exists(expr.getChild(index)) or index = 0) + 1
+    )
+  }
 
   override string getProperty(string key) {
     result = super.getProperty(key)
@@ -439,6 +446,11 @@ class StmtNode extends AstNode {
         result.getAst() = child.(Stmt)
       )
     )
+    or
+    exists(int destructorIndex |
+      result.getAst() = stmt.getImplicitDestructorCall(destructorIndex) and
+      childIndex = destructorIndex + max(int index | exists(stmt.getChild(index)) or index = 0) + 1
+    )
   }
 
   override string getChildAccessorPredicateInternal(int childIndex) {
@@ -662,13 +674,22 @@ private string getChildAccessorWithoutConversions(Locatable parent, Element chil
       or
       not namedStmtChildPredicates(s, child, _) and
       exists(int n | s.getChild(n) = child and result = "getChild(" + n + ")")
+      or
+      exists(int n |
+        s.getImplicitDestructorCall(n) = child and result = "getImplicitDestructorCall(" + n + ")"
+      )
     )
     or
     exists(Expr expr | expr = parent |
       namedExprChildPredicates(expr, child, result)
       or
       not namedExprChildPredicates(expr, child, _) and
       exists(int n | expr.getChild(n) = child and result = "getChild(" + n + ")")
+      or
+      exists(int n |
+        expr.getImplicitDestructorCall(n) = child and
+        result = "getImplicitDestructorCall(" + n + ")"
+      )
     )
   )
 }

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

@@ -58,6 +58,19 @@ class Expr extends StmtParent, @expr {
   /** Gets the parent of this expression, if any. */
   Element getParent() { exprparents(underlyingElement(this), _, unresolveElement(result)) }
 
+  /**
+   * Gets the `n`th compiler-generated destructor call that is performed after this expression, in
+   * order of destruction.
+   */
+  DestructorCall getImplicitDestructorCall(int n) {
+    synthetic_destructor_call(this, max(int i | synthetic_destructor_call(this, i, _)) - n, result)
+  }
+
+  /**
+   * Gets a compiler-generated destructor call that is performed after this expression.
+   */
+  DestructorCall getAnImplicitDestructorCall() { synthetic_destructor_call(this, _, result) }
+
   /** Gets the location of this expression. */
   override Location getLocation() {
     result = this.getExprLocationOverride()

cpp/ql/lib/semmle/code/cpp/stmts/Stmt.qll

@@ -59,6 +59,28 @@ class Stmt extends StmtParent, @stmt {
     )
   }
 
+  /**
+   * Gets the `n`th compiler-generated destructor call that is performed after this statement, in
+   * order of destruction.
+   *
+   * For instance, in the following code, `getImplicitDestructorCall(0)` for the block will be the
+   * destructor call for `c2`:
+   * ```cpp
+   * {
+   *      MyClass c1;
+   *      MyClass c2;
+   * }
+   * ```
+   */
+  DestructorCall getImplicitDestructorCall(int n) {
+    synthetic_destructor_call(this, max(int i | synthetic_destructor_call(this, i, _)) - n, result)
+  }
+
+  /**
+   * Gets a compiler-generated destructor call that is performed after this statement.
+   */
+  DestructorCall getAnImplicitDestructorCall() { synthetic_destructor_call(this, _, result) }
+
   override Location getLocation() { stmts(underlyingElement(this), _, result) }
 
   override string toString() { none() }