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, 10 insertions, 0 deletions

diff --git a/test/src/callproc-tests.el b/test/src/callproc-tests.el
index bf7d47b27f1..1617d5e33d3 100644
--- a/test/src/callproc-tests.el
+++ b/test/src/callproc-tests.el
@@ -66,4 +66,14 @@
                   (error :got-error))))
     (should have-called-debugger)))
 
+(ert-deftest call-process-region-entire-buffer-with-delete ()
+  "Check that Bug#40576 is fixed."
+  (let ((emacs (expand-file-name invocation-name invocation-directory)))
+    (skip-unless (file-executable-p emacs))
+    (with-temp-buffer
+      (insert "Buffer contents\n")
+      (should
+       (eq (call-process-region nil nil emacs :delete nil nil "--version") 0))
+      (should (eq (buffer-size) 0)))))
+
 ;;; callproc-tests.el ends here