Index: setup.py
===================================================================
--- setup.py	(revision 74738)
+++ setup.py	(working copy)
@@ -546,16 +546,16 @@
 
         # readline
         do_readline = self.compiler_obj.find_library_file(lib_dirs, 'readline')
-        if platform == 'darwin': # and os.uname()[2] < '9.':
+        # Mac OS X 10.5 and 10.6 (Darwin 9 and 10) are OK.
+        os_release = int(os.uname()[2].split('.')[0])
+        if platform == 'darwin' and os_release < 9:
             # MacOSX 10.4 has a broken readline. Don't try to build
             # the readline module unless the user has installed a fixed
             # readline package
-            # FIXME: The readline emulation on 10.5 is better, but the
-            # readline module doesn't compile out of the box.
             if find_file('readline/rlconf.h', inc_dirs, []) is None:
                 do_readline = False
         if do_readline:
-            if sys.platform == 'darwin':
+            if sys.platform == 'darwin' and os_release < 9:
                 # In every directory on the search path search for a dynamic
                 # library and then a static library, instead of first looking
                 # for dynamic libraries on the entiry path.
Index: Modules/readline.c
===================================================================
--- Modules/readline.c	(revision 74738)
+++ Modules/readline.c	(working copy)
@@ -6,6 +6,7 @@
 
 /* Standard definitions */
 #include "Python.h"
+#include <stdlib.h>
 #include <setjmp.h>
 #include <signal.h>
 #include <errno.h>
@@ -976,10 +977,23 @@
 	n = strlen(p);
 	if (n > 0) {
 		char *line;
+		char *e = "EditLine wrapper";
 		HISTORY_STATE *state = history_get_history_state();
-		if (state->length > 0)
-			line = history_get(state->length)->line;
-		else
+		if (state->length > 0) {
+			/*
+			 * On Mac OS X 10.5, readline is emulated.
+			 * When there's only one line in history, the
+			 * original statement (in the "else" part below)
+			 * causes out-of-bounds access and BusError.
+			 * The fix is applied only if r_library_version
+			 * is "EditLine wrapper" because the original
+			 * statement works for GNU readline.
+			 */
+			if (strncmp(rl_library_version, e, strlen(e)) == 0)
+				line = history_get(state->length - 1)->line;
+			else
+				line = history_get(state->length)->line;
+		} else
 			line = "";
 		if (strcmp(p, line))
 			add_history(p);