>From 2f75e0d7b3800faee1c7bffe76b06ba36e67c305 Mon Sep 17 00:00:00 2001
From: Brand Huntsman <address@hidden>
Date: Fri, 20 Oct 2017 21:26:20 -0600
Subject: [PATCH] prevent position history overwrites across multiple instances
 of nano

Signed-off-by: Brand Huntsman <address@hidden>
---
 src/global.c  |  1 +
 src/history.c | 38 ++++++++++++++++++++++++++++++++++++++
 src/nano.c    |  1 -
 src/proto.h   |  2 +-
 4 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/global.c b/src/global.c
index 13a138dd..f846759b 100644
--- a/src/global.c
+++ b/src/global.c
@@ -221,6 +221,7 @@ filestruct *execute_history = NULL;
 filestruct *executetop = NULL;
 filestruct *executebot = NULL;
 
+struct stat position_history_stat;
 poshiststruct *position_history = NULL;
 	/* The list of filenames with their last cursor positions. */
 #endif
diff --git a/src/history.c b/src/history.c
index 11cf6c20..95644153 100644
--- a/src/history.c
+++ b/src/history.c
@@ -378,6 +378,14 @@ void save_history(void)
     free(histname);
 }
 
+/* Update modification time of position history file. */
+void update_poshistory_timestamp(void)
+{
+    char *poshist = poshistfilename();
+    stat(poshist, &position_history_stat);
+    free(poshist);
+}
+
 /* Load the recorded cursor positions for files that were edited. */
 void load_poshistory(void)
 {
@@ -440,6 +448,8 @@ void load_poshistory(void)
 	}
 	fclose(hisfile);
 	free(line);
+
+	update_poshistory_timestamp();
     }
     free(poshist);
 }
@@ -479,10 +489,32 @@ void save_poshistory(void)
 	    free(path_and_place);
 	}
 	fclose(hisfile);
+
+	update_poshistory_timestamp();
     }
     free(poshist);
 }
 
+/* Re-load position history file if it has been modified since last load. */
+void reload_poshistory(void)
+{
+    struct stat st;
+    char *poshist = poshistfilename();
+    stat(poshist, &st);
+    free(poshist);
+    if (position_history_stat.st_mtime < st.st_mtime) {
+	poshiststruct *posptr, *posnext;
+	for (posptr = position_history; posptr != NULL; posptr = posnext) {
+	    posnext = posptr->next;
+	    free(posptr->filename);
+	    free(posptr);
+	}
+	position_history = NULL;
+
+	load_poshistory();
+    }
+}
+
 /* Update the recorded last file positions, given a filename, a line
  * and a column.  If no entry is found, add a new one at the end. */
 void update_poshistory(char *filename, ssize_t lineno, ssize_t xpos)
@@ -495,6 +527,8 @@ void update_poshistory(char *filename, ssize_t lineno, ssize_t xpos)
 	return;
     }
 
+    reload_poshistory();
+
     /* Look for a matching filename in the list. */
     for (posptr = position_history; posptr != NULL; posptr = posptr->next) {
 	if (!strcmp(posptr->filename, fullpath))
@@ -543,6 +577,8 @@ void update_poshistory(char *filename, ssize_t lineno, ssize_t xpos)
     theone->next = NULL;
 
     free(fullpath);
+
+    save_poshistory();
 }
 
 /* Check whether the given file matches an existing entry in the recorded
@@ -556,6 +592,8 @@ bool has_old_position(const char *file, ssize_t *line, ssize_t *column)
     if (fullpath == NULL)
 	return FALSE;
 
+    reload_poshistory();
+
     while (posptr != NULL && strcmp(posptr->filename, fullpath) != 0)
 	posptr = posptr->next;
 
diff --git a/src/nano.c b/src/nano.c
index b3888d9d..5cc7e94b 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -570,7 +570,6 @@ void finish(void)
 	save_history();
     if (ISSET(POS_HISTORY)) {
 	update_poshistory(openfile->filename, openfile->current->lineno, xplustabs() + 1);
-	save_poshistory();
     }
 #endif
 
diff --git a/src/proto.h b/src/proto.h
index 2bc7fe7a..160591be 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -168,6 +168,7 @@ extern filestruct *replacebot;
 extern filestruct *execute_history;
 extern filestruct *executetop;
 extern filestruct *executebot;
+extern struct stat position_history_stat;
 extern poshiststruct *position_history;
 #endif
 
@@ -368,7 +369,6 @@ bool have_dotnano(void);
 void load_history(void);
 void save_history(void);
 void load_poshistory(void);
-void save_poshistory(void);
 void update_poshistory(char *filename, ssize_t lineno, ssize_t xpos);
 bool has_old_position(const char *file, ssize_t *line, ssize_t *column);
 #endif
-- 
2.13.6