From 5a4e13eda683f1f0182035b7d56666465fd1c7f8 Mon Sep 17 00:00:00 2001
From: Marko Lindqvist <cazfi74@gmail.com>
Date: Sun, 26 Jun 2022 01:57:54 +0300
Subject: [PATCH 55/55] Rework readline cleanup on server quit

- Introduce readline_atexit()
- Call rl_callback_handler_remove() from readline_atexit()
- Do not register rl_callback_handler_remove() as atexit function
- Free last input line (the one where the "quit" command was given)
  in readline_atexit()
- Call readline_atexit() from server_quit(), before exit()
  This clear things before any atexit handlers installed by tools
  wrapping freeciv
- Also register readline_atexit() as atexit function, to make sure
  it gets called at least once even when server_quit() is bypassed
  for any reason

See osdn #44948

Signed-off-by: Marko Lindqvist <cazfi74@gmail.com>
---
 server/sernet.c   | 44 +++++++++++++++++++++++++++++++++++---------
 server/sernet.h   |  6 ++++--
 server/srv_main.c |  1 +
 3 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/server/sernet.c b/server/sernet.c
index 9a53f4eb5e..686d13efeb 100644
--- a/server/sernet.c
+++ b/server/sernet.c
@@ -161,18 +161,15 @@ static void handle_stdin_close(void)
 #define HISTORY_LENGTH    100
 
 static char *history_file = NULL;
-
 static bool readline_handled_input = FALSE;
-
 static bool readline_initialized = FALSE;
+static char *current_internal = NULL;
 
 /*************************************************************************//**
   Readline callback for input.
 *****************************************************************************/
 static void handle_readline_input_callback(char *line)
 {
-  char *line_internal;
-
   if (no_input) {
     return;
   }
@@ -187,15 +184,44 @@ static void handle_readline_input_callback(char *line)
   }
 
   con_prompt_enter();      /* just got an 'Enter' hit */
-  line_internal = local_to_internal_string_malloc(line);
-  (void) handle_stdin_input(NULL, line_internal);
-  free(line_internal);
-  free(line);
+  current_internal = local_to_internal_string_malloc(line);
+  free(line); /* This is already freed if we exit() with /quit command */
+  (void) handle_stdin_input(NULL, current_internal);
+  free(current_internal); /* Since handle_stdin_input() returned,
+                           * we can be sure this was not freed in atexit. */
+  current_internal = NULL;
 
   readline_handled_input = TRUE;
 }
 #endif /* FREECIV_HAVE_LIBREADLINE */
 
+/*************************************************************************//**
+  Clear readline stuff at exit. To cater for as many different cases as
+  possible, we call this both like any function call from server_quit()
+  before exit(), and as a atexit handler. Former is to get everything
+  cleared already before exit(), before any other atexit handler comes
+  to play. Latter is to make sure that the function gets called also when
+  in those rare cases where we exit some other way than server_quit() -
+  that's important for always restoring terminal to a working state.
+
+  That means that in usual case this function gets called twice.
+  Make sure that it doesn't try double frees or similar when that happens.
+*****************************************************************************/
+void readline_atexit(void)
+{
+#ifdef FREECIV_HAVE_READLINE
+  if (readline_initialized) {
+    rl_callback_handler_remove();
+    readline_initialized = FALSE;
+  }
+
+  if (current_internal != NULL) {
+    free(current_internal);
+    current_internal = NULL;
+  }
+#endif /* FREECIV_HAVE_LIBREADLINE */
+}
+
 /*************************************************************************//**
   Close the connection (very low-level). See also
   server_conn_close_callback().
@@ -542,7 +568,7 @@ enum server_events server_sniff_all_input(void)
       rl_attempted_completion_function = freeciv_completion;
 
       readline_initialized = TRUE;
-      atexit(rl_callback_handler_remove);
+      atexit(readline_atexit);
     }
   }
 #endif /* FREECIV_HAVE_LIBREADLINE */
diff --git a/server/sernet.h b/server/sernet.h
index 015844d3b8..fcbe8e60ef 100644
--- a/server/sernet.h
+++ b/server/sernet.h
@@ -1,4 +1,4 @@
-/********************************************************************** 
+/***********************************************************************
  Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -42,8 +42,10 @@ int server_make_connection(int new_sock,
 void handle_conn_pong(struct connection *pconn);
 void handle_client_heartbeat(struct connection *pconn);
 
+void readline_atexit(void);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
 
-#endif  /* FC__SERNET_H */
+#endif /* FC__SERNET_H */
diff --git a/server/srv_main.c b/server/srv_main.c
index da156a4a7f..957496883e 100644
--- a/server/srv_main.c
+++ b/server/srv_main.c
@@ -1877,6 +1877,7 @@ void fc__noreturn server_quit(void)
   free_nls();
   con_log_close();
   cmdline_option_values_free();
+  readline_atexit();
   exit(EXIT_SUCCESS);
 }
 
-- 
2.35.1