From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 15 Nov 2021 08:32:41 +0000 (+0100)
Subject: docs: mention RET_NERRNO() in CODING_STYLE.md
X-Git-Tag: v250-rc1~248
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=947796eac385651f6a66fc0ce925a301b49f6fa4;p=thirdparty%2Fsystemd.git

docs: mention RET_NERRNO() in CODING_STYLE.md
---

diff --git a/docs/CODING_STYLE.md b/docs/CODING_STYLE.md
index 34e04ed735a..eba1e1444e6 100644
--- a/docs/CODING_STYLE.md
+++ b/docs/CODING_STYLE.md
@@ -285,6 +285,25 @@ SPDX-License-Identifier: LGPL-2.1-or-later
   one cause, it *really* should have an `int` as the return value for the error
   code.
 
+- libc system calls typically return -1 on error (with the error code in
+  `errno`), and >= 0 on success. Use the RET_NERRNO() helper if you are looking
+  for a simple way to convert this libc style error returning into systemd
+  style error returning. e.g.
+
+  ```c
+  …
+  r = RET_NERRNO(unlink(t));
+  …
+  ```
+
+  or
+
+  ```c
+  …
+  r = RET_NERRNO(open("/some/file", O_RDONLY|O_CLOEXEC));
+  …
+  ```
+
 - Do not bother with error checking whether writing to stdout/stderr worked.
 
 - Do not log errors from "library" code, only do so from "main program"