Calling a C Function without Prototype
void foo(const char *name) {
    printf("foo called with %sn", name);
}

void bar(int a) {
    printf("bar called with %dn", a);
}

int main(int argc, char *argv[]) {
    foo("Hello");
    bar(5);
    return 0;
}

gcc -fno-builtin -ansi -c -o foo.o foo.c
gcc -fno-builtin -ansi -c -o bar.o bar.c
gcc -fno-builtin -ansi -c -o main.o main.c

gcc -o progy main.o bar.o foo.o

ld -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o progy  /usr/lib64/crt1.o /usr/lib64/crti.o /usr/lib/gcc/x86_64-unknown-linux-gnu/4.6.1/crtbegin.o main.o foo.o bar.o -lc  -L/usr/lib/gcc/x86_64-unknown-linux-gnu/4.6.1 -lgcc -lgcc_s /usr/lib/gcc/x86_64-unknown-linux-gnu/4.6.1/crtend.o /usr/lib64/crtn.o