File 0176-Fix-race-condition-in-standard_error-process-registr.patch of Package erlang

From 6b6f7f92e7011c27da115bf1e633137f497e2f9a Mon Sep 17 00:00:00 2001
From: Nelson Vides <videsnelson@gmail.com>
Date: Thu, 16 Oct 2025 17:38:14 +0200
Subject: [PATCH] Fix race condition in standard_error process registration

Fix a race condition where the standard_error process could call
prim_tty:init/1 before being registered, causing a crash when prim_tty's
writer and reader processes attempt to derive their own registered names
from the parent process.

The issue was introduced in commit
ead74245e1dc632b8f20ee795092de04d2510e36 (PR #9116), which changed
prim_tty's reader and writer processes to dynamically derive their
registered names from their parent process name (e.g., 'standard_error'
-> 'standard_error_reader', 'standard_error_writer'). This was done
to support multiple TTY instances (stdout and stderr) with
distinct process names.

However, the standard_error:start/0 function had a race condition:
1. spawn(fun server/0) - creates process, starts executing immediately
2. register(?NAME, Id) - parent registers the spawned process
3. server() calls prim_tty:init() - may execute before step 2

When prim_tty:init/1 spawns writer/reader processes, they call
set_name(Parent, Postfix) which does: erlang:process_info(Parent,
registered_name)

If this executes before the parent completes registration, it returns []
instead of {registered_name, standard_error}, causing a pattern match
failure: "no match of right hand side value: []" at prim_tty.erl:674.

The fix moves the register/2 call into the spawned process itself,
ensuring it completes before prim_tty:init/1 is called. This eliminates
the race condition entirely.

Closes #10174
---
 lib/kernel/src/standard_error.erl | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/kernel/src/standard_error.erl b/lib/kernel/src/standard_error.erl
index c887ac70c6..51a296d7d3 100644
--- a/lib/kernel/src/standard_error.erl
+++ b/lib/kernel/src/standard_error.erl
@@ -62,12 +62,11 @@ init([]) ->
     end.
 
 start() ->
-    Id = spawn(fun server/0),
-    register(?NAME, Id),
-    Id.
+    spawn(fun server/0).
 
 server() ->
     process_flag(trap_exit, true),
+    register(?NAME, self()),
     ok = prim_tty:load(),
     TTY = prim_tty:init(#{ input => disabled,
                            output => cooked,
-- 
2.51.0