__attribute__ ((default)) 和 __attribute__ ((hidden))

1 /* a.h */
2 int func();

1 /* a.c */
2 #include <stdio.h>
3 #include "a.h"
4 
5 int func()
6 {
7     printf("### func ###\n");
8     return 0;
9 }

gcc -shared -o liba.so a.c -fPIC

1 #include "a.h"
2 
3 int main()
4 {
5     func();
6     return 0
7 }

gcc -o main main.c -la -L. -Wl,-rpath=.

__attribute__((visibility("hidden")))

/tmp/ccbxiXwp.o: In function `main‘:
main.c:(.text+0x7): undefined reference to `func‘
collect2: error: ld returned 1 exit status