View Compilation Error

0_0_8093695_3777.cpp: In function `char* BigNumAdd(char*, char*, int)':
0_0_8093695_3777.cpp:28: error: `strrev' undeclared (first use this function)
0_0_8093695_3777.cpp:28: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8093695_3777.cpp:55: error: name lookup of `j' changed for new ISO `for' scoping
0_0_8093695_3777.cpp:51: error:   using obsolete binding at `j'