__ATTRIBUTE__ ((default)) and __attribute__ ((hidden))

Make a shared library

1 /*  */2int func ();

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

Gcc-shared-o liba.so A.c-fpic

Main.c

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

Gcc-o main main.c-la-l.-wl,-rpath=.

If you precede func with the

__ATTRIBUTE__ ((Visibility ("hidden")))

When compiling main, error:

/tmp/ccbxixwp.o:in function ' main':main.c: (. text+0x7): Undefined reference to ' func'  1 exit status

If you add-fvisibility=hidden when compiling a dynamic library , the symbols for the dynamic library are hidden

Add __attribute__ ((Visibility ("default")) before the function to make the function visible to the outside

__ATTRIBUTE__ ((default)) and __attribute__ ((hidden))