Fix error in 'call-process-region' when START is nil (Bug#40576)

* src/callproc.c (Fcall_process_region): Fix behavior when START is
nil and DELETE is non-nil.

* test/src/callproc-tests.el
(call-process-region-entire-buffer-with-delete): New unit test.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/callproc.c b/src/callproc.c
index 8883415f3f5..65c858393a9 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1099,7 +1099,17 @@ usage: (call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &r
     }
 
   if (nargs > 3 && !NILP (args[3]))
-    Fdelete_region (start, end);
+    {
+      if (NILP (start))
+        {
+          /* No need to save restrictions since we delete everything
+             anyway.  */
+          Fwiden ();
+          del_range (BEG, Z);
+        }
+      else
+        Fdelete_region (start, end);
+    }
 
   if (nargs > 3)
     {