C++: Test for PointlessComparison with templates

jbj · jbj · commit 2eea359f79fb · 2018-10-03T14:47:00.000+02:00
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected b/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected
@@ -32,3 +32,7 @@
 | PointlessComparison.c:129:12:129:16 | ... > ... | Comparison is always false because a <= 3. |
 | PointlessComparison.c:197:7:197:11 | ... < ... | Comparison is always false because x >= 0. |
 | RegressionTests.cpp:57:7:57:22 | ... <= ... | Comparison is always true because * ... <= 4294967295. |
+| Templates.cpp:3:10:3:24 | ... <= ... | Comparison is always true because param <= 32767. |
+| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |
+| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |
+| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/Templates.cpp b/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/Templates.cpp
@@ -0,0 +1,17 @@
+template<typename T>
+bool sometimesPointless(T param) {
+  return param <= 0xFFFF; // GOOD (FALSE POSITIVE: hypothetical instantiations are okay)
+}
+
+template<typename T>
+bool alwaysPointless(T param) {
+  short local = param;
+  return local <= 0xFFFF; // BAD (in all instantiations)
+}
+
+static int caller(int i) {
+  return
+      sometimesPointless<short>(i) ||
+      alwaysPointless<short>(i) ||
+      alwaysPointless<int>(i);
+}
