C++: suppress destructors on conditional temporaries

Robert Marsh · MathiasVP · commit 17e8c95e7f94 · 2024-04-04T11:28:10.000+01:00
diff --git a/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedElement.qll b/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedElement.qll
@@ -127,6 +127,11 @@ private predicate ignoreExprAndDescendants(Expr expr) {
   exists(BuiltInVarArgsStart vaStartExpr |
     vaStartExpr.getLastNamedParameter().getFullyConverted() = expr
   )
+  or
+  // Do not translate implicit destructor calls for unnamed temporary variables that are
+  // conditionally constructed (until we have a mechanism for calling these only when the
+  // temporary's constructor was run)
+  isConditionalTemporaryDestructorCall(expr)
 }
 
 /**
@@ -252,6 +257,20 @@ private predicate usedAsCondition(Expr expr) {
   )
 }
 
+private predicate isInConditionalEvaluation(Expr e) {
+  exists(ConditionalExpr cond |
+    e = cond.getThen() and not cond.isTwoOperand()
+    or
+    e = cond.getElse()
+  )
+  or
+  isInConditionalEvaluation(getRealParent(e))
+}
+
+private predicate isConditionalTemporaryDestructorCall(DestructorCall dc) {
+  isInConditionalEvaluation(dc.getQualifier().(ReuseExpr).getReusedExpr())
+}
+
 /**
  * Holds if `conv` is an `InheritanceConversion` that requires a `TranslatedLoad`, despite not being
  * marked as having an lvalue-to-rvalue conversion.
