C++: Exclude comparisons from enum constants in `cpp/constant-comparison

Author: jketema

cpp/ql/src/Likely Bugs/Arithmetic/PointlessComparison.ql

@@ -25,14 +25,16 @@ import UnsignedGEZero
 //
 // So to reduce the number of false positives, we do not report a result if
 // the comparison is in a macro expansion. Similarly for template
-// instantiations, static asserts, non-type template arguments, and constexprs.
+// instantiations, static asserts, non-type template arguments, enum constants,
+// and constexprs.
 from ComparisonOperation cmp, SmallSide ss, float left, float right, boolean value, string reason
 where
   not cmp.isInMacroExpansion() and
   not cmp.isFromTemplateInstantiation(_) and
   not exists(StaticAssert s | s.getCondition() = cmp.getParent*()) and
   not exists(Declaration d | d.getATemplateArgument() = cmp.getParent*()) and
   not exists(Variable v | v.isConstexpr() | v.getInitializer().getExpr() = cmp.getParent*()) and
+  not exists(EnumConstant e | e.getInitializer().getExpr() = cmp.getParent*()) and
   not functionContainsDisabledCode(cmp.getEnclosingFunction()) and
   reachablePointlessComparison(cmp, left, right, value, ss) and
   // a comparison between an enum and zero is always valid because whether

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected

@@ -50,5 +50,4 @@
 | PointlessComparison.cpp:43:6:43:29 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327.5. |
 | PointlessComparison.cpp:44:6:44:28 | ... >= ... | Comparison is always true because ... >> ... >= 140737488355327.5. |
 | RegressionTests.cpp:57:7:57:22 | ... <= ... | Comparison is always true because * ... <= 4294967295. |
-| RegressionTests.cpp:165:9:165:33 | ... > ... | Comparison is always true because ... * ... >= 64. |
 | Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/RegressionTests.cpp

@@ -162,5 +162,5 @@ struct A_Struct {
 };
 
 enum E {
-  E_e = sizeof(A_Struct) * 8 > 50 // GOOD [FALSE POSITIVE]
+  E_e = sizeof(A_Struct) * 8 > 50 // GOOD
 };