C++: Fix missing result by properly specifying that the function with unknown code actually didn't throw an exception.

Author: MathiasVP

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/IncorrectAllocationErrorHandling.expected

@@ -14,4 +14,5 @@
 | test.cpp:93:15:93:41 | new[] | This allocation cannot throw. $@ is unnecessary. | test.cpp:97:36:98:3 | { ... } | This catch block |
 | test.cpp:96:10:96:36 | new[] | This allocation cannot throw. $@ is unnecessary. | test.cpp:97:36:98:3 | { ... } | This catch block |
 | test.cpp:151:9:151:24 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:152:15:152:18 | { ... } | This catch block |
+| test.cpp:199:15:199:35 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:201:16:201:19 | { ... } | This catch block |
 | test.cpp:212:14:212:34 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:213:34:213:36 | { ... } | This catch block |

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/test.cpp

@@ -158,10 +158,10 @@ void good_placement_new_with_exception_handling() {
   catch (...) {  }
 }
 
-int rand();
+int unknown_value_without_exceptions() noexcept;
 
 void may_throw() {
-  if(rand()) {
+  if(unknown_value_without_exceptions()) {
     throw "bad luck exception!";
   }
 }
@@ -170,11 +170,11 @@ void unknown_code_that_may_throw(int*);
 void unknown_code_that_will_not_throw(int*) noexcept;
 
 void calls_throwing_code(int* p) {
-  if(rand()) unknown_code_that_may_throw(p);
+  if(unknown_value_without_exceptions()) unknown_code_that_may_throw(p);
 }
 
 void calls_non_throwing(int* p) {
-  if (rand()) unknown_code_that_will_not_throw(p);
+  if (unknown_value_without_exceptions()) unknown_code_that_will_not_throw(p);
 }
 
 void good_new_with_throwing_call() {
@@ -196,7 +196,7 @@ void good_new_with_throwing_call() {
 
 void bad_new_with_nonthrowing_call() {
   try {
-    int* p1 = new(std::nothrow) int; // BAD [NOT DETECTED]
+    int* p1 = new(std::nothrow) int; // BAD
     calls_non_throwing(p1);
   } catch(...) {  }