C++: Include Assignments in exprMayThrow and accept test changes.

Author: MathiasVP

cpp/ql/src/experimental/Security/CWE/CWE-570/IncorrectAllocationErrorHandling.ql

@@ -127,6 +127,10 @@ predicate exprMayThrow(Expr e) {
     convertedExprMayThrow([binOp.getLeftOperand(), binOp.getRightOperand()])
   )
   or
+  exists(Assignment assign | assign = e |
+    convertedExprMayThrow([assign.getLValue(), assign.getRValue()])
+  )
+  or
   exists(CommaExpr comma | comma = e |
     convertedExprMayThrow([comma.getLeftOperand(), comma.getRightOperand()])
   )

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

@@ -16,4 +16,3 @@
 | 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 |
-| test.cpp:219:9:219:15 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:220:34:220:36 | { ... } | This catch block |

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

@@ -216,6 +216,6 @@ void bad_new_catch_baseclass_of_bad_alloc() {
 void good_new_catch_exception_in_assignment() {
   int* p;
   try {
-    p = new int; // GOOD [FALSE POSITIVE]
+    p = new int; // GOOD
   } catch(const std::bad_alloc&) { }
 }