View Compilation Error

0_0_1643559_19384.cpp: In function `int searchMaxSubString(char*)':
0_0_1643559_19384.cpp:20: error: `strrev' undeclared (first use this function)
0_0_1643559_19384.cpp:20: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1643559_19384.cpp: At global scope:
0_0_1643559_19384.cpp:34: error: `main' must return `int'