Rule 8.13: Handle multiple copies

If the same code is compiled multiple times, variables may be const
in one case but non-const in another. Handle this by requiring all
such copies to be const-able before flagging.

Author: lcartey

c/misra/src/rules/RULE-8-13/PointerShouldPointToConstTypeWhenPossible.ql

@@ -18,29 +18,47 @@ import cpp
 import codingstandards.c.misra
 import codingstandards.cpp.Pointers
 import codingstandards.cpp.SideEffect
+import codingstandards.cpp.alertreporting.HoldsForAllCopies
 
-from Variable ptr, PointerOrArrayType type
+class NonConstPointerVariableCandidate extends Variable {
+  NonConstPointerVariableCandidate() {
+    // Avoid elements in macro expansions, as they cannot be equated across copies
+    not this.isInMacroExpansion() and
+    exists(PointerOrArrayType type |
+      // include only pointers which point to a const-qualified type
+      this.getType() = type and
+      not type.isDeeplyConstBelow()
+    ) and
+    // exclude pointers passed as arguments to functions which take a
+    // parameter that points to a non-const-qualified type
+    not exists(FunctionCall fc, int i |
+      fc.getArgument(i) = this.getAnAccess() and
+      not fc.getTarget().getParameter(i).getType().isDeeplyConstBelow()
+    ) and
+    // exclude any pointers which have their underlying data modified
+    not exists(VariableEffect effect |
+      effect.getTarget() = this and
+      // but not pointers that are only themselves modified
+      not effect.(AssignExpr).getLValue() = effect.getAnAccess() and
+      not effect.(CrementOperation).getOperand() = effect.getAnAccess()
+    ) and
+    // exclude pointers assigned to another pointer to a non-const-qualified type
+    not exists(Variable a |
+      a.getAnAssignedValue() = this.getAnAccess() and
+      not a.getType().(PointerOrArrayType).isDeeplyConstBelow()
+    )
+  }
+}
+
+/**
+ * Ensure that all copies of a variable are considered to be missing const qualification to avoid
+ * false positives where a variable is only used/modified in a single copy.
+ */
+class NonConstPointerVariable =
+  HoldsForAllCopies<NonConstPointerVariableCandidate, Variable>::LogicalResultElement;
+
+from NonConstPointerVariable ptr
 where
-  not isExcluded(ptr, Pointers1Package::pointerShouldPointToConstTypeWhenPossibleQuery()) and
-  // include only pointers which point to a const-qualified type
-  ptr.getType() = type and
-  not type.isDeeplyConstBelow() and
-  // exclude pointers passed as arguments to functions which take a
-  // parameter that points to a non-const-qualified type
-  not exists(FunctionCall fc, int i |
-    fc.getArgument(i) = ptr.getAnAccess() and
-    not fc.getTarget().getParameter(i).getType().isDeeplyConstBelow()
-  ) and
-  // exclude any pointers which have their underlying data modified
-  not exists(VariableEffect effect |
-    effect.getTarget() = ptr and
-    // but not pointers that are only themselves modified
-    not effect.(AssignExpr).getLValue() = effect.getAnAccess() and
-    not effect.(CrementOperation).getOperand() = effect.getAnAccess()
-  ) and
-  // exclude pointers assigned to another pointer to a non-const-qualified type
-  not exists(Variable a |
-    a.getAnAssignedValue() = ptr.getAnAccess() and
-    not a.getType().(PointerOrArrayType).isDeeplyConstBelow()
-  )
-select ptr, "$@ points to a non-const-qualified type.", ptr, ptr.getName()
+  not isExcluded(ptr.getAnElementInstance(),
+    Pointers1Package::pointerShouldPointToConstTypeWhenPossibleQuery())
+select ptr, "$@ points to a non-const-qualified type.", ptr, ptr.getAnElementInstance().getName()