linux - How can dlsym successfully import function from stripped binary library? -

it's weird dlsym can import functions stripped binaries.

can tell me why/how?

=== file: a.c === int a1() { return 1; } int a2() { return 2; } === end of a.c ===  === file: b.c === #include <stdio.h> #include <dlfcn.h> #include <stdlib.h>  typedef int (*fint)();  fint dlsym_fint(void *handle, char *name) {     fint x = (fint)dlsym(handle, name);     char *err = null;     if ((err = dlerror()) != null) {         printf("dlsym: %s\n", err);         exit(1);     }     return x; }  int main() {     void *dl = dlopen("a.so", rtld_now);     fint = null;     = dlsym_fint(dl, "a1");     printf("%p: %d\n", a, a());     = dlsym_fint(dl, "a2");     printf("%p: %d\n", a, a());     return 0; } === end of b.c ===  $ gcc -shared -fpic -o a.so a.c $ nm a.so ... 00000000000004ec t a1 00000000000004f7 t a2 ...  $ strip a.so $ nm a.so nm: a.so: no symbols  $ gcc -o b b.c -ldl  $ ./b 0x2aaaaaac74ec: 1 0x2aaaaaac74f7: 2 

try readelf -s a.so. dynamic symbols still there after strip.

(or switch nm -d a.so.)