From 1e9bcbb54b9e593c79236da7fc82cb5435aec757 Mon Sep 17 00:00:00 2001
From: Lucas Alves <lucas@lkzeu.com>
Date: Mon, 6 Apr 2026 21:57:32 -0300
Subject: [PATCH] Add asio::basic_errors::not_supported
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As noted by Vinícius dos Santos¹, ENOTSUP and EOPNOTSUPP may alias
on some systems. That's the case for Linux and FreeBSD.

On Systems where ENOTSUP and EOPNOTSUPP have the same errno values,
one might inadvertently catch EOPNOTSUPP when a composed operation
throws ENOTSUP. There's nothing ASIO can do here, so we don't try to.

Reference:
¹https://sourceforge.net/p/asio/mailman/message/58710157/
---
 include/asio/error.hpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/asio/error.hpp b/include/asio/error.hpp
index 56c1ad4006..acd17d14da 100644
--- a/include/asio/error.hpp
+++ b/include/asio/error.hpp
@@ -162,6 +162,9 @@ enum basic_errors
   /// Socket operation on non-socket.
   not_socket = ASIO_SOCKET_ERROR(ENOTSOCK),
 
+  // Not supported.
+  not_supported = ASIO_NATIVE_ERROR(ENOTSUP),
+
   /// Operation cancelled.
   operation_aborted = ASIO_WIN_OR_POSIX(
       ASIO_NATIVE_ERROR(ERROR_OPERATION_ABORTED),