Index: configure.in
===================================================================
--- configure.in	(revision 67033)
+++ configure.in	(working copy)
@@ -276,12 +276,19 @@
   # but used in struct sockaddr.sa_family. Reported by Tim Rice.
   SCO_SV/3.2)
     define_xopen_source=no;;
-  # On FreeBSD 4.8 and MacOS X 10.2, a bug in ncurses.h means that
-  # it craps out if _XOPEN_EXTENDED_SOURCE is defined. Apparently,
-  # this is fixed in 10.3, which identifies itself as Darwin/7.*
-  # This should hopefully be fixed in FreeBSD 4.9
-  FreeBSD/4.8* | Darwin/6* )
+  # On FreeBSD 4, the math functions C89 does not cover are never defined
+  # with _XOPEN_SOURCE and __BSD_VISIBLE does not re-enable them.
+  FreeBSD/4.*)
     define_xopen_source=no;;
+  # On MacOS X 10.2, a bug in ncurses.h means that it craps out if 
+  # _XOPEN_EXTENDED_SOURCE is defined. Apparently, this is fixed in 10.3, which
+  # identifies itself as Darwin/7.*
+  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
+  # disables platform specific features beyond repair.
+  # On Mac OS X 10.3, defining _POSIX_C_SOURCE or _XOPEN_SOURCE 
+  # has no effect, don't bother defining them
+  Darwin/@<:@6789@:>@.*)
+    define_xopen_source=no;;
   # On AIX 4 and 5.1, mbstate_t is defined only when _XOPEN_SOURCE == 500 but
   # used in wcsnrtombs() and mbsnrtowcs() even if _XOPEN_SOURCE is not defined
   # or has another value. By not (re)defining it, the defaults come in place.
@@ -292,13 +299,6 @@
       define_xopen_source=no
     fi
     ;;
-  # On Mac OS X 10.4, defining _POSIX_C_SOURCE or _XOPEN_SOURCE
-  # disables platform specific features beyond repair.
-  # On Mac OS X 10.3, defining _POSIX_C_SOURCE or _XOPEN_SOURCE 
-  # has no effect, don't bother defining them
-  Darwin/@<:@789@:>@.*)
-    define_xopen_source=no
-    ;;
   # On QNX 6.3.2, defining _XOPEN_SOURCE prevents netdb.h from
   # defining NI_NUMERICHOST.
   QNX/6.3.2)
Index: setup.py
===================================================================
--- setup.py	(revision 67033)
+++ setup.py	(working copy)
@@ -1261,7 +1261,7 @@
                 )
             libraries = []
 
-        elif platform in ('freebsd5', 'freebsd6', 'freebsd7', 'freebsd8'):
+        elif platform in ('freebsd4', 'freebsd5', 'freebsd6', 'freebsd7', 'freebsd8'):
             # FreeBSD's P1003.1b semaphore support is very experimental
             # and has many known problems. (as of June 2008)
             macros = dict(                  # FreeBSD
Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 67033)
+++ Misc/NEWS	(working copy)
@@ -50,6 +50,8 @@
 
 - Issue #3758: Add ``patchcheck`` build target to .PHONY.
 
+- Issue #4204: Fixed module build errors on FreeBSD 4.
+
 C-API
 -----
 
Index: Modules/readline.c
===================================================================
--- Modules/readline.c	(revision 67033)
+++ Modules/readline.c	(working copy)
@@ -35,8 +35,12 @@
 #define completion_matches(x, y) \
 	rl_completion_matches((x), ((rl_compentry_func_t *)(y)))
 #else
+#if defined(_RL_FUNCTION_TYPEDEF)
 extern char **completion_matches(char *, rl_compentry_func_t *);
+#else
+extern char **completion_matches(char *, CPFunction *);
 #endif
+#endif
 
 static void
 on_completion_display_matches_hook(char **matches,
@@ -213,8 +217,12 @@
 	   default completion display. */
 	rl_completion_display_matches_hook =
 		completion_display_matches_hook ?
+#if defined(_RL_FUNCTION_TYPEDEF)
 		(rl_compdisp_func_t *)on_completion_display_matches_hook : 0;
+#else
+		(VFunction *)on_completion_display_matches_hook : 0;
 #endif
+#endif
 	return result;
 
 }
Index: Modules/_multiprocessing/multiprocessing.h
===================================================================
--- Modules/_multiprocessing/multiprocessing.h	(revision 67033)
+++ Modules/_multiprocessing/multiprocessing.h	(working copy)
@@ -20,7 +20,9 @@
 #  define SEM_VALUE_MAX LONG_MAX
 #else
 #  include <fcntl.h>                 /* O_CREAT and O_EXCL */
+#  include <netinet/in.h>
 #  include <sys/socket.h>
+#  include <sys/uio.h>
 #  include <arpa/inet.h>             /* htonl() and ntohl() */
 #  if HAVE_SEM_OPEN
 #    include <semaphore.h>