xref: /dflybsd-src/lib/libc/gen/dlvsym.3 (revision 4a5f69f602439e4ddaa5c06d3f350823dac88dd0)

.\" This source code is a product of Sun Microsystems, Inc. and is provided
.\" for unrestricted use provided that this legend is included on all tape
.\" media and as a part of the software program in whole or part.  Users
.\" may copy or modify this source code without charge, but are not authorized
.\" to license or distribute it to anyone else except as part of a product or
.\" program developed by the user.
.\"
.\" THIS PROGRAM CONTAINS SOURCE CODE COPYRIGHTED BY SUN MICROSYSTEMS, INC.
.\" SUN MICROSYSTEMS, INC., MAKES NO REPRESENTATIONS ABOUT THE SUITABLITY
.\" OF SUCH SOURCE CODE FOR ANY PURPOSE.  IT IS PROVIDED "AS IS" WITHOUT
.\" EXPRESS OR IMPLIED WARRANTY OF ANY KIND.  SUN MICROSYSTEMS, INC. DISCLAIMS
.\" ALL WARRANTIES WITH REGARD TO SUCH SOURCE CODE, INCLUDING ALL IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN
.\" NO EVENT SHALL SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY SPECIAL, INDIRECT,
.\" INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
.\" FROM USE OF SUCH SOURCE CODE, REGARDLESS OF THE THEORY OF LIABILITY.
.\"
.\" This source code is provided with no support and without any obligation on
.\" the part of Sun Microsystems, Inc. to assist in its use, correction,
.\" modification or enhancement.
.\"
.\" SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
.\" INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS
.\" SOURCE CODE OR ANY PART THEREOF.
.\"
.\" Sun Microsystems, Inc.
.\" 2550 Garcia Avenue
.\" Mountain View, California 94043
.\"
.\" Copyright (c) 1991 Sun Microsystems, Inc.
.\"
.\" $FreeBSD: src/lib/libc/gen/dlopen.3 211397 2010-08-16 15:18:30Z joel $
.\"
.Dd February 22, 2018
.Dt DLVSYM 3
.Os
.Sh NAME
.Nm dlvsym
.Nd shared object symbol lookup by version function
.Sh LIBRARY
This function is not in a library.
It is included in every dynamically linked program automatically.
.Sh SYNOPSIS
.In dlfcn.h
.Ft "void *"
.Fn dlvsym "void * restrict handle" "const char * restrict name" "const char * restrict version"
.Sh DESCRIPTION
The
.Fn dlvsym
function
does the same as
.Xr 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.
.Sh NOTES
ELF executables need to be linked
using the
.Fl export-dynamic
option to
.Xr ld 1
for symbols defined in the executable to become visible to
.Fn dlvsym .
.Sh RETURN VALUES
The
.Fn 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
.Fn dlerror .
.Sh 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.
.Bd -literal
#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\en", 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\en",
                "__addvsi3", "GCC_3.0");
       dlclose (handle);
       exit (EXIT_FAILURE);
    }

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

    exit(EXIT_SUCCESS);
}
.Ed
.Sh SEE ALSO
.Xr rtld 1 ,
.Xr dlfcn 3 ,
.Xr dlsym 3
.Sh HISTORY
The
.Nm
function first appeared in
.Dx 2.11 .