M.cpp:9:11: error: '::main' must return 'int'
M.cpp: In function 'int main()':
M.cpp:23:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
M.cpp: In function 'bool isOK(char*)':
M.cpp:36:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
M.cpp:39:10: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null]
M.cpp:42:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
M.cpp:45:24: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null]
M.cpp:48:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
M.cpp:51:24: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null]
M.cpp: In function 'char* strRev(char*)':
M.cpp:71:12: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null]
M.cpp:67:7: warning: address of local variable 'result' returned [enabled by default]
M.cpp: In function 'int main()':
M.cpp:11:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]