RULE-2-2: Exclude cases nested in macro expansions

Author: lcartey

c/misra/src/rules/RULE-2-2/DeadCode.ql

@@ -14,6 +14,7 @@
 
 import cpp
 import codingstandards.c.misra
+import codingstandards.cpp.alertreporting.HoldsForAllInstances
 import codingstandards.cpp.deadcode.UselessAssignments
 
 /**
@@ -39,6 +40,9 @@ class DeadOperation extends Expr {
   string description;
 
   DeadOperation() {
+    // Exclude cases nested within macro expansions, because the code may be "live" in other
+    // expansions
+    isNotWithinMacroExpansion(this) and
     exists(ExprStmtExpr e |
       if exists(getExplicitCast(e))
       then

c/misra/test/rules/RULE-2-2/DeadCode.expected

@@ -5,3 +5,5 @@
 | test.c:23:3:23:30 | (int)... | Cast operation is unused. |
 | test.c:24:3:24:25 | (int)... | Cast operation is unused. |
 | test.c:27:4:27:18 | call to no_side_effects | Result of operation is unused and has no side effects. |
+| test.c:37:3:37:27 | call to no_side_effects | Result of operation is unused and has no side effects. |
+| test.c:38:7:38:31 | call to no_side_effects | Result of operation is unused and has no side effects. |

c/misra/test/rules/RULE-2-2/test.c

@@ -26,5 +26,17 @@ int test_dead_code(int x) {
   (may_have_side_effects());    // COMPLIANT
   (no_side_effects(x));         // NON_COMPLIANT
 
+#define FULL_STMT_NO_SIDE_EFFECTS no_side_effects(1);
+#define PART_STMT_NO_SIDE_EFFECTS no_side_effects(1)
+#define BLOCK_SOME_SIDE_EFFECTS                                                \
+  {                                                                            \
+    may_have_side_effects();                                                   \
+    no_side_effects(1);                                                        \
+  }
+
+  FULL_STMT_NO_SIDE_EFFECTS      // NON_COMPLIANT
+      PART_STMT_NO_SIDE_EFFECTS; // NON_COMPLIANT
+  BLOCK_SOME_SIDE_EFFECTS;       // COMPLIANT
+
   return live5 + live6; // COMPLIANT
 }

cpp/common/src/codingstandards/cpp/alertreporting/HoldsForAllInstances.qll

@@ -20,14 +20,19 @@
 import cpp
 
 /**
- * Holds if the `Stmt` `s` is not within a macro expansion, i.e. generated by a macro, but not the
- * outermost `Stmt` generated by the macro.
+ * Holds if the `Element` `e` is not within a macro expansion, i.e. generated by a macro, but not
+ * the outermost `Stmt` or `Expr` generated by the macro.
  */
-predicate isNotWithinMacroExpansion(Stmt s) {
-  not s.isInMacroExpansion()
+predicate isNotWithinMacroExpansion(Element e) {
+  not e.isInMacroExpansion()
   or
   exists(MacroInvocation mi |
-    mi.getStmt() = s and
+    mi.getStmt() = e
+    or
+    mi.getExpr() = e
+    or
+    mi.getStmt().(ExprStmt).getExpr() = e
+  |
     not exists(mi.getParentInvocation())
   )
 }