DragonFly On-Line Manual Pages

DLVSYM(3)             DragonFly Library Functions Manual             DLVSYM(3)

NAME
     dlvsym -- shared object symbol lookup by version function

LIBRARY
     This function is not in a library.  It is included in every dynamically
     linked program automatically.

SYNOPSIS
     #include <dlfcn.h>

     void *
     dlvsym(void * restrict handle, const char * restrict name,
         const char * restrict version);

DESCRIPTION
     The dlvsym() function does the same as dlsym(3) but takes a version
     string as an additional argument.  Both the name and the version must
     match in order for the symbol to be resolved.

NOTES
     ELF executables need to be linked using the -export-dynamic option to
     ld(1) for symbols defined in the executable to become visible to
     dlvsym().

RETURN VALUES
     The dlvsym() function returns the address of the symbol unless the symbol
     can not be found.  In this case, it returns a null pointer and sets an
     error condition which may be queried with dlerror().

EXAMPLES
     The following program will obtain a pointer to the gcc library __adsvsi3
     function using dlvsym specified to version GCC_3.0, and then it will use
     it to print out the sum of 500 + 325.

     #include <dlfcn.h>
     #include <stdlib.h>
     #include <stdio.h>

     int
     main (int argc, char *argv[])
     {
         void       *handle;
         int        (*func_sum)(int a, int b);

         /* open the dports shared gcc410 library  */
         handle = dlopen("/usr/local/lib/gcc410/libgcc_s.so", RTLD_LAZY);
         if (!handle) {
            fprintf (stderr, "%s\n", dlerror ());
            exit (EXIT_FAILURE);
         }

         /* get pointer to integer sum function */
         func_sum = dlvsym (handle, "__addvsi3", "GCC_3.0");
         if (func_sum == NULL) {
            fprintf (stderr, "function %s version %s not found\n",
                     "__addvsi3", "GCC_3.0");
            dlclose (handle);
            exit (EXIT_FAILURE);
         }

         /* Calculate and display the sum of 500 + 325 */
         printf ("500 + 325 = %d\n", func_sum((int)500, (int)325));
         dlclose (handle);

         exit(EXIT_SUCCESS);
     }

SEE ALSO
     rtld(1), dlfcn(3), dlsym(3)

HISTORY
     The dlvsym function first appeared in DragonFly 2.11.

DragonFly 5.5                  February 22, 2018                 DragonFly 5.5