C++: Demonstrate a FP due to GVN

jbj · jbj · commit 120df6054bc2 · 2019-05-30T09:41:42.000+02:00
diff --git a/cpp/ql/test/query-tests/Likely Bugs/RedundantNullCheckSimple/RedundantNullCheckSimple.cpp b/cpp/ql/test/query-tests/Likely Bugs/RedundantNullCheckSimple/RedundantNullCheckSimple.cpp
@@ -100,3 +100,13 @@ void test_field_local(bool boolvar) {
     }
   }
 }
+
+struct S {
+  long **pplong;
+
+  void test_phi() {
+    while (*pplong != nullptr) { // GOOD [FALSE POSITIVE]
+      pplong++;
+    }
+  }
+};
diff --git a/cpp/ql/test/query-tests/Likely Bugs/RedundantNullCheckSimple/RedundantNullCheckSimple.expected b/cpp/ql/test/query-tests/Likely Bugs/RedundantNullCheckSimple/RedundantNullCheckSimple.expected
@@ -3,3 +3,4 @@
 | RedundantNullCheckSimple.cpp:48:12:48:12 | Load: p | This null check is redundant because the value is $@ in any case | RedundantNullCheckSimple.cpp:51:10:51:11 | Load: * ... | dereferenced here |
 | RedundantNullCheckSimple.cpp:79:7:79:9 | Load: * ... | This null check is redundant because the value is $@ in any case | RedundantNullCheckSimple.cpp:78:7:78:10 | Load: * ... | dereferenced here |
 | RedundantNullCheckSimple.cpp:93:13:93:13 | Load: p | This null check is redundant because the value is $@ in any case | RedundantNullCheckSimple.cpp:92:13:92:18 | Load: * ... | dereferenced here |
+| RedundantNullCheckSimple.cpp:108:12:108:18 | Load: * ... | This null check is redundant because the value is $@ in any case | RedundantNullCheckSimple.cpp:108:12:108:18 | Load: * ... | dereferenced here |

Original file line number	Diff line number	Diff line change
`@@ -100,3 +100,13 @@ void test_field_local(bool boolvar) {`
`100`	`100`	`}`
`101`	`101`	`}`
`102`	`102`	`}`
	`103`	`+`
	`104`	`+struct S {`
	`105`	`+ long **pplong;`
	`106`	`+`
	`107`	`+ void test_phi() {`
	`108`	`+ while (*pplong != nullptr) { // GOOD [FALSE POSITIVE]`
	`109`	`+ pplong++;`
	`110`	`+ }`
	`111`	`+ }`
	`112`	`+};`