bug#41640: 28.0.50; shell startup very slow when init file is used

[Pip Cet]

Jan Synacek <jsynacek@redhat.com> writes:
> It takes almost 2 seconds before the shell buffer appears and Emacs is
> frozen in the mean time. Without the init file, the shell buffer appears
> instantly.

Can you try this patch?

>From d5f1df0edfe6f5d4b178d30d78567bec223927ee Mon Sep 17 00:00:00 2001
From: Pip Cet <pipcet@gmail.com>
Date: Thu, 4 Jun 2020 21:18:10 +0000
Subject: [PATCH] Avoid 1s sleep-for before sending the startfile to a comint
 process

* lisp/comint.el (comint-exec): Simplify startup file code.
(Bug#41640)
---
 lisp/comint.el | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/lisp/comint.el b/lisp/comint.el
index ea06f8af87..4354a155c3 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -809,18 +809,10 @@ comint-exec
       (goto-char (point-max))
       (set-marker (process-mark proc) (point))
       ;; Feed it the startfile.
-      (cond (startfile
-            ;;This is guaranteed to wait long enough
-            ;;but has bad results if the comint does not prompt at all
-            ;;      (while (= size (buffer-size))
-            ;;        (sleep-for 1))
-            ;;I hope 1 second is enough!
-            (sleep-for 1)
-            (goto-char (point-max))
-            (insert-file-contents startfile)
-            (setq startfile (buffer-substring (point) (point-max)))
-            (delete-region (point) (point-max))
-            (comint-send-string proc startfile)))
+      (when startfile
+        (comint-send-string proc (with-temp-buffer
+                                   (insert-file-contents startfile)
+                                   (buffer-string))))
       (run-hooks 'comint-exec-hook)
       buffer)))
 
-- 
2.27.0.rc0