View Compilation Error

0_0_7373850_4326.cpp: In function `int_64 area(int)':
0_0_7373850_4326.cpp:15: error: invalid conversion from `void*' to `stack_item*'
0_0_7373850_4326.cpp:45: error: `printf' undeclared (first use this function)
0_0_7373850_4326.cpp:45: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7373850_4326.cpp: In function `int main()':
0_0_7373850_4326.cpp:54: error: `scanf' undeclared (first use this function)