bpo-29854: Fix segfault in call_readline()

Lib/test/test_readline.py

@@ -9,7 +9,7 @@
 import sys
 import tempfile
 import unittest
-from test.support import import_module, unlink, TESTFN
+from test.support import import_module, unlink, temp_dir, TESTFN
 from test.support.script_helper import assert_python_ok
 
 # Skip tests if there is no readline module
@@ -210,13 +210,50 @@ def display(substitution, matches, longest_match_length):
         self.assertIn(b"result " + expected + b"\r\n", output)
         self.assertIn(b"history " + expected + b"\r\n", output)
 
+    @unittest.skipIf(is_editline,
+                     "editline history size configuration is broken")
+    def test_history_size(self):
+        history_size = 10
+        with temp_dir() as test_dir:
+            inputrc = os.path.join(test_dir, "inputrc")
+            with open(inputrc, "wb") as f:
+                f.write(b"set history-size %d\n" % history_size)
+
+            history_file = os.path.join(test_dir, "history")
+            with open(history_file, "wb") as f:
+                # history_size * 2 items crashes readline
+                data = b"".join(b"item %d\n" % i
+                                for i in range(history_size * 2))
+                f.write(data)
+
+            script = """
+import os
+import readline
+
+history_file = os.environ["HISTORY_FILE"]
+readline.read_history_file(history_file)
+input()
+readline.write_history_file(history_file)
+"""
+
+            env = dict(os.environ)
+            env["INPUTRC"] = inputrc
+            env["HISTORY_FILE"] = history_file
+
+            run_pty(script, input=b"last input\r", env=env)
+
+            with open(history_file, "rb") as f:
+                lines = f.readlines()
+            self.assertEqual(len(lines), history_size)
+            self.assertEqual(lines[-1].strip(), b"last input")
+
 
-def run_pty(script, input=b"dummy input\r"):
+def run_pty(script, input=b"dummy input\r", env=None):
     pty = import_module('pty')
     output = bytearray()
     [master, slave] = pty.openpty()
     args = (sys.executable, '-c', script)
-    proc = subprocess.Popen(args, stdin=slave, stdout=slave, stderr=slave)
+    proc = subprocess.Popen(args, stdin=slave, stdout=slave, stderr=slave, env=env)
     os.close(slave)
     with ExitStack() as cleanup:
         cleanup.enter_context(proc)

Misc/NEWS.d/next/Library/2017-07-07-02-18-57.bpo-29854.J8wKb_.rst

@@ -0,0 +1,2 @@
+Fix segfault in readline when using readline's history-size option.  Patch
+by Nir Soffer.

Modules/readline.c

@@ -1347,15 +1347,17 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
     if (should_auto_add_history && n > 0) {
         const char *line;
         int length = _py_get_history_length();
-        if (length > 0)
+        if (length > 0) {
+            HIST_ENTRY *hist_ent;
 #ifdef __APPLE__
             if (using_libedit_emulation) {
                 /* handle older 0-based or newer 1-based indexing */
-                line = (const char *)history_get(length + libedit_history_start - 1)->line;
+                hist_ent = history_get(length + libedit_history_start - 1);
             } else
 #endif /* __APPLE__ */
-            line = (const char *)history_get(length)->line;
-        else
+                hist_ent = history_get(length);
+            line = hist_ent ? hist_ent->line : "";
+        } else
             line = "";
         if (strcmp(p, line))
             add_history(p);