foo.cpp:5:0: warning: "NULL" redefined [enabled by default]
 #define NULL nullptr
 ^
In file included from c:\mingw\include\stdlib.h:22:0,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\cstdlib:72,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\bits\stl_algo.h:59,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\algorithm:62,
                 from foo.cpp:4:
c:\mingw\lib\gcc\mingw32\4.8.1\include\stddef.h:399:0: note: this is the location of the previous definition
 #define NULL __null
 ^
foo.cpp:57:5: warning: identifier 'nullptr' is a keyword in C++11 [-Wc++0x-compat]
     long long num = strtoll(M.c_str(), nullptr, N);
     ^
foo.cpp: In function 'int main()':
foo.cpp:57:40: error: 'nullptr' was not declared in this scope
     long long num = strtoll(M.c_str(), nullptr, N);
                                        ^