いくら話題が無いからって、おまいらつられすぎww
キャスト使えば一発だろJK

#include <stdint.h>

int func1(int i) { return ( uint8_t)i; }
int func2(int i) { return ( int8_t)i; }
int func3(int i) { return (uint16_t)i; }
int func4(int i) { return ( int16_t)i; }
int func5(int i, int *j) { *j = i / 4294967296ULL; return i; }

main() {
int j = 0xcafebabe;
printf("%08x\n", func1(0xdeadbeef));
printf("%08x\n", func2(0xdeadbeef));
printf("%08x\n", func3(0xdeadbeef));
printf("%08x\n", func4(0xdeadbeef));
printf("%08x, ", func5(0xdeadbeef, &j));
printf("%08x\n", j);
}