C++: Exclude more comparisons from cpp/constant-comparison

Author: jketema

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

@@ -25,11 +25,14 @@ 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.
+// instantiations, static asserts, non-type template arguments, 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 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

@@ -50,9 +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:131:17:131:25 | ... < ... | Comparison is always true because 43 <= ... + .... |
-| RegressionTests.cpp:135:26:135:52 | ... < ... | Comparison is always false because 16 >= ... * .... |
-| RegressionTests.cpp:140:50:140:61 | ... < ... | Comparison is always false because ... * ... >= 84. |
-| RegressionTests.cpp:154:21:154:31 | ... < ... | Comparison is always false because ... - ... >= 34. |
-| RegressionTests.cpp:154:21:154:31 | ... < ... | Comparison is always false because ... - ... >= 38. |
 | Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |

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

@@ -128,17 +128,17 @@ void testTempObject() {
 void staticAssert() {
   static const int a = 42;
   static const int b = 43;
-  static_assert(a < b + 0, ""); // GOOD [FALSE POSITIVE]
+  static_assert(a < b + 0, ""); // GOOD
 }
 
 constexpr int global_1 = 42;
-constexpr int global_2 = global_1 < 2 * sizeof(int*) ? 43 : 2 * sizeof(int*); // GOOD [FALSE POSITIVE]
+constexpr int global_2 = global_1 < 2 * sizeof(int*) ? 43 : 2 * sizeof(int*); // GOOD
 
 static const int global_3 = 42;
 static const int global_4 = global_3 < 2 * sizeof(int*) ? 43 : 2 * sizeof(int*); // GOOD
 
 template<unsigned int p, unsigned int n, bool = ((2u * n) < p)>
-struct templateCompare : public templateCompare<p, 2u * n>  // GOOD [FALSE POSITIVE]
+struct templateCompare : public templateCompare<p, 2u * n>  // GOOD
 { };
 
 template< unsigned int p, unsigned int n>
@@ -151,7 +151,7 @@ unsigned int templateCompare_x = templateCompare<42, 42>::v;
 
 template<int n>
 struct someType {
-  typedef someType<((n - 4) < 0 ? 0 : n - 4)> b;  // GOOD [FALSE POSITIVE]
+  typedef someType<((n - 4) < 0 ? 0 : n - 4)> b;  // GOOD
 };
 
 someType<42>::b someType_x;