listener: use temp file when saving history.

We don't want ot overwrite the history file in-place; if
something goes wrong, we will lose half of it.

* parser.c (repl): Save the history to a .tmp file, and
then rename that to the target name, if the write is
successful.

1 files changed, 8 insertions, 2 deletions

diff --git a/parser.c b/parser.c
index 778fad12..8212fdd7 100644
--- a/parser.c
+++ b/parser.c
@@ -1376,8 +1376,14 @@ val repl(val bindings, val in_stream, val out_stream)
 
   dyn_env = saved_dyn_env;
 
-  if (histfile_w)
-    lino_hist_save(ls, histfile_w);
+  if (histfile_w) {
+    val histfile_tmp = format(nil, lit("~a/.txr_history.tmp"), home, nao);
+    if (lino_hist_save(ls, c_str(histfile_tmp)) == 0)
+      rename_path(histfile_tmp, histfile);
+    else
+      put_line(lit("** unable to save history file"), out_stream);
+    gc_hint(histfile_tmp);
+  }
 
   free(line_w);
   lino_free(ls);