Add a new function dlversion() which returns the version number of

the dynamic linker in the same form as __FreeBSD_version.  This is
mainly intended for checking the dynamic linker version during a make
world.

include/dlfcn.h

@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id$
+ *	$Id: dlfcn.h,v 1.2 1998/02/11 05:19:10 jdp Exp $
  */
 
 #ifndef _DLFCN_H_
@@ -66,6 +66,7 @@ int dlclose __P((void *));
 const char *dlerror __P((void));
 void *dlopen __P((const char *, int));
 void *dlsym __P((void *, const char *));
+int dlversion __P((void));
 __END_DECLS
 
 #endif /* !_DLFCN_H_ */

lib/libc/gen/dlfcn.c

@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: dlfcn.c,v 1.1 1998/02/09 06:05:24 jdp Exp $
+ *	$Id: dlfcn.c,v 1.2 1998/03/07 19:57:05 jdp Exp $
  */
 
 /*
@@ -94,6 +94,14 @@ dlsym(void *handle, const char *name)
 	return NULL;
 }
 
+#pragma weak dlversion
+int
+dlversion(void)
+{
+	_rtld_error(sorry);
+	return 0;
+}
+
 #else /* a.out format */
 
 #include <sys/types.h>
@@ -165,4 +173,11 @@ dlsym(void *handle, const char *name)
 		return (__ldso_entry->dlsym)(handle, name);
 }
 
+/* We don't support dlversion() on a.out systems. */
+int
+dlversion(void)
+{
+	return 0;
+}
+
 #endif /* __ELF__ */

lib/libc/gen/dlopen.3

@@ -34,7 +34,7 @@
 .Os FreeBSD
 .Dt DLOPEN 3
 .Sh NAME
-.Nm dlopen, dlsym, dlerror, dlclose
+.Nm dlopen, dlsym, dlerror, dlclose, dlversion
 .Nd programmatic interface to the dynamic linker
 .Sh SYNOPSIS
 .Fd #include <dlfcn.h>
@@ -46,6 +46,8 @@
 .Fn dlerror "void"
 .Ft int
 .Fn dlclose "void *handle"
+.Ft int
+.Fn dlversion "void"
 .Sh DESCRIPTION
 These functions provide a simple programmatic interface to the services of the
 dynamic linker.
@@ -219,6 +221,19 @@ The object-intrinsic functions
 and
 .Fn _fini
 are called with no arguments, and are not expected to return values.
+.Pp
+.Fn dlversion
+returns the version number of the dynamic linker.  Interpreted
+as a decimal number, the version number has the form
+.Em rrrsss .
+.Em rrr
+corresponds to the base operating system release version, e.g., 400
+for release 4.0.0.
+.Em sss
+is a serial number that increases monotonically within each release
+version.  If the installed dynamic linker is too old to support
+.Fn dlversion ,
+0 is returned.
 .Sh NOTES
 ELF executables need to be linked
 using the
@@ -234,6 +249,8 @@ and
 return the null pointer in the event of errors.
 .Fn dlclose
 returns 0 on success, or -1 if an error occurred.
+.Fn dlversion
+returns 0 if the dynamic linker is too old to support it.
 Whenever an error has been detected, a message detailing it can be
 retrieved via a call to
 .Fn dlerror .

libexec/rtld-elf/rtld.c

@@ -22,7 +22,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *      $Id: rtld.c,v 1.16 1999/04/04 06:01:09 peter Exp $
+ *      $Id: rtld.c,v 1.17 1999/04/05 02:36:40 jdp Exp $
  */
 
 /*
@@ -51,6 +51,14 @@
 #include "debug.h"
 #include "rtld.h"
 
+/*
+ * Version number queried by dlversion().  The first 3 digits represent
+ * the base FreeBSD release.  The last 3 digits are a serial number.
+ * Increase this when you fix a significant bug or add a significant
+ * feature.
+ */
+#define DL_VERSION	400001
+
 /*
  * Debugging support.
  */
@@ -152,6 +160,7 @@ static func_ptr_type exports[] = {
     (func_ptr_type) &dlopen,
     (func_ptr_type) &dlsym,
     (func_ptr_type) &dladdr,
+    (func_ptr_type) &dlversion,
     NULL
 };
 
@@ -1272,6 +1281,12 @@ dlsym(void *handle, const char *name)
     return NULL;
 }
 
+int
+dlversion(void)
+{
+    return DL_VERSION;
+}
+
 int
 dladdr(const void *addr, Dl_info *info)
 {