C++: Fix a FP in cpp/wrong-number-format-arguments caused by extraction error

Author: calumgrant

cpp/ql/src/Likely Bugs/Format/WrongNumberOfFormatArguments.ql

@@ -44,7 +44,8 @@ where
   ) and
   // A typical problem is that string literals are concatenated, but if one of the string
   // literals is an undefined macro, then this just leads to a syntax error.
-  not exists(SyntaxError e | e.affects(fl))
+  not exists(SyntaxError e | e.affects(fl)) and
+  not ffc.getArgument(_) instanceof ErrorExpr
 select ffc,
   "Format for " + ffcName + " expects " + expected.toString() + " arguments but given " +
     given.toString()

cpp/ql/test/query-tests/Likely Bugs/Format/WrongNumberOfFormatArguments/WrongNumberOfFormatArguments.expected

@@ -5,7 +5,6 @@
 | macros.cpp:14:2:14:37 | call to printf | Format for printf (in a macro expansion) expects 4 arguments but given 3 |
 | macros.cpp:21:2:21:36 | call to printf | Format for printf (in a macro expansion) expects 4 arguments but given 3 |
 | macros.cpp:32:2:32:25 | call to printf | Format for printf (in a macro expansion) expects 1 arguments but given 0 |
-| syntax_errors.c:8:5:8:10 | call to printf | Format for printf expects 2 arguments but given 1 |
 | test.c:9:2:9:7 | call to printf | Format for printf expects 1 arguments but given 0 |
 | test.c:12:2:12:7 | call to printf | Format for printf expects 2 arguments but given 1 |
 | test.c:15:2:15:7 | call to printf | Format for printf expects 3 arguments but given 2 |