c - symbol lookup error: ./libobjdata.so: undefined symbol: bfd_map_over_sections -

when compiled getsections_dl.c file, output error, mean have not linked library?

my compile command is:

gcc getsections_dl.c -l. -ldl -lbfd -o getsections_dl 

my getsections_dl.c:

#include <stdlib.h> #include <string.h> #include <bfd.h> #include <unistd.h> #include <dlfcn.h>  extern void dump_sections(bfd *abfd); #define rdtsc(x)    __asm__ __volatile__("rdtsc \n\t" : "=a" (*(x)))    // following function tweaked version of itoa functions // can found in either objsym.c or objsect.c char* lltoa(long long int val, int base) {   if (val == 0x0) {    static char zero[] = "0";    return &zero[0];   }   static char buf[64] = {0};   int = 60;   for(; val && ; --i, val /= base)     buf[i] = "0123456789abcdef"[val % base];   return &buf[i+1]; }   int main(int argc, char *argv[]) {   bfd *obj;   void *handle;   unsigned long long start, finish;     void (*func)(bfd *);    bfd_init();    obj = bfd_openr(argv[1], "elf32-i386");   if (!obj) {     bfd_perror("open failure\n");     return 0;   }    rdtsc(&start);    if (!strcmp(argv[2], "rtld_lazy"))     handle = dlopen("./libobjdata.so", rtld_lazy);   else     handle = dlopen("./libobjdata.so", rtld_now);    rdtsc(&finish);    bfd_check_format(obj, bfd_object);     //compute cycles   write(1, "time: ", strlen("time: "));   int t = (finish-start)/2793;   write(1, lltoa(t, 10), strlen(lltoa(t, 10)));   write(1, " cycles/mhz\n\n", strlen(" cycles/mhz\n\n"));      func = dlsym(handle, "dump_sections");   // bfd_map_over_sections(obj, func2, null);   dump_sections(obj);   dlclose(handle);    return 0; } 

and library c file objsect.c (which objdump() dose):

#include <bfd.h> #include <stdio.h> #include <unistd.h> #include <string.h>  void dump_section(bfd *abfd, asection *section, void *obj) {     // number of octets per target byte     //unsigned int opb = bfd_octets_per_byte(abfd);    char* itoa(int val, int base) {   if (val == 0x0) {    static char zero[] = "0";    return &zero[0];   }   static char buf[32] = {0};   int = 30;   for(; val && ; --i, val /= base)     buf[i] = "0123456789abcdef"[val % base];   return &buf[i+1]; }    //write(1, "section:", strlen("section:")); write(1, section->name, strlen(section->name)); write(1, " \t", strlen(" \t")); write(1, itoa(section->vma, 16), strlen(itoa(section->vma, 16))); write(1, " \t", strlen(" \t")); write(1, itoa(section->rawsize, 16), strlen(itoa(section->rawsize, 10))); write(1, " \t", strlen(" \t")); write(1, itoa(section->size, 16), strlen(itoa(section->size, 10))); write(1, " \t", strlen(" \t")); write(1, itoa(section->filepos, 16), strlen(itoa(section->filepos, 16))); write(1, " \n", strlen(" \n")); }  void dump_sections(bfd *abfd) {      write(1, "name\t", strlen("name\t"));      write(1, "size\t", strlen("size\t"));      write(1, "vma\tt", strlen("vma\t"));     write(1, "lma\t", strlen("lma\t"));     write(1, "file off\t", strlen("file off\t"));     write(1, "algn\n", strlen("algn\n"));  // each section in abfd, call dump_section_headers()     bfd_map_over_sections(abfd, dump_section, null); }