C++: Add test case.

Author: geoffw0

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedStaticFunctions/UnusedStaticFunctions.expected

@@ -1,3 +1,5 @@
+| extraction_error.c:4:13:4:43 | my_function2_called_after_error | Static function my_function2_called_after_error is unreachable | extraction_error.c:4:13:4:43 | my_function2_called_after_error | my_function2_called_after_error |
+| extraction_error.c:5:13:5:35 | my_function3_not_called | Static function my_function3_not_called is unreachable | extraction_error.c:5:13:5:35 | my_function3_not_called | my_function3_not_called |
 | unused_functions.c:16:13:16:27 | unused_function | Static function unused_function is unreachable | unused_functions.c:16:13:16:27 | unused_function | unused_function |
 | unused_functions.c:20:13:20:28 | unused_function2 | Static function unused_function2 is unreachable ($@ must be removed at the same time) | unused_functions.c:24:13:24:28 | unused_function3 | unused_function3 |
 | unused_functions.c:24:13:24:28 | unused_function3 | Static function unused_function3 is unreachable | unused_functions.c:24:13:24:28 | unused_function3 | unused_function3 |

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedStaticFunctions/extraction_error.c

@@ -0,0 +1,15 @@
+// semmle-extractor-options: --expect_errors
+
+static void my_function1_called() {} // GOOD
+static void my_function2_called_after_error() {} // GOOD [FALSE POSITIVE]
+static void my_function3_not_called() {} // BAD
+
+int main(void) {
+	my_function1_called();
+
+--- compilation stops here because this line is not valid C code ---
+
+	my_function2_called_after_error();
+
+	return 0;
+}