[bill@billstone make_lib]$ cat pr1.c
#include <stdio.h>
void print1(void)
{
                printf("This is the first lib src!/n");
}
[bill@billstone make_lib]$ cat pr2.c
#include<stdio.h>
void print2(void)
{
                printf("This is the second src lib!/n");
}
[bill@billstone make_lib]$ cat main.c
int main(void)
{
                print1();
                print2();
                return 0;
} 

[bill@billstone make_lib]$ gcc -O -c pr1.c pr2.c
[bill@billstone make_lib]$ ls -l pr*.o
-rw-rw-r--        1 bill          bill                    804    4 月  15 11:11 pr1.o
-rw-rw-r--        1 bill          bill                    804    4 月  15 11:11 pr2.o

[bill@billstone make_lib]$ cat pr1.c
#include <stdio.h>
int p = 2;
void print(){
                printf("%p:%d/n", &p, p);
                printf("This is the first dll src!/n");
}

[bill@billstone make_lib]$ gcc -O -fpic -shared -o xxx.so pr1.c
[bill@billstone make_lib]$ ls -l *.so
-rwxrwxr-x        1 bill          bill                  6592    4 月  15 15:19 xxx.so

[bill@billstone make_lib]$ cat main.c
int main()
{
       print();
       return 0;
}
[bill@billstone make_lib]$ gcc -o main main.c ./xxx.so
[bill@billstone make_lib]$ ./main
0x97b5d4:2
this is the first lib src!