Hi Bruno,
We're about to use the copy-file module in iwhd,
and I'm seeing this warning/error with our gcc options:
copy-file.c: In function 'copy_file_preserving':
copy-file.c:120:9: error: ignoring return value of 'chown', declared with
attribute warn_unused_result [-Wunused-result]
I see two ways to address the problem.
One is to add this pragma along with a comment somewhere in copy-file.c:
# pragma GCC diagnostic ignored "-Wunused-result"
but that seems unwise. In a file like that, it would be all too easy to
introduce a real bug that would be warned about by -Wunused-result.
IMHO, we must not turn off that option.
How about this patch instead?
>From 6b8f3f6439d77ad4b84765eaee9eab501bd0d4de Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@redhat.com>
Date: Tue, 1 Mar 2011 15:20:33 +0100
Subject: [PATCH] copy-file: ignore warning about chown's unused return value
* lib/copy-file.c: Include "ignore-value.h".
(copy_file_preserving): Ignore chown failure.
* modules/copy-file (Depends-on): Add ignore-value.
---
ChangeLog | 7 +++++++
lib/copy-file.c | 3 ++-
modules/copy-file | 1 +
3 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index ceff3bf..1d85cf7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2011-03-01 Jim Meyering <meyer...@redhat.com>
+
+ copy-file: ignore warning about chown's unused return value
+ * lib/copy-file.c: Include "ignore-value.h".
+ (copy_file_preserving): Ignore chown failure.
+ * modules/copy-file (Depends-on): Add ignore-value.
+
2011-02-28 Paul Eggert <egg...@cs.ucla.edu>
stdio: simplify by moving files to printf-posix, sigpipe
diff --git a/lib/copy-file.c b/lib/copy-file.c
index f9cd9c0..27a35c2 100644
--- a/lib/copy-file.c
+++ b/lib/copy-file.c
@@ -42,6 +42,7 @@
#include "acl.h"
#include "binary-io.h"
#include "gettext.h"
+#include "ignore-value.h"
#include "xalloc.h"
#define _(str) gettext (str)
@@ -117,7 +118,7 @@ copy_file_preserving (const char *src_filename, const char
*dest_filename)
#if HAVE_CHOWN
/* Preserve the owner and group. */
- chown (dest_filename, statbuf.st_uid, statbuf.st_gid);
+ ignore_value (chown (dest_filename, statbuf.st_uid, statbuf.st_gid));
#endif
/* Preserve the access permissions. */
diff --git a/modules/copy-file b/modules/copy-file
index 6941e5a..ab25b6b 100644
--- a/modules/copy-file
+++ b/modules/copy-file
@@ -13,6 +13,7 @@ error
exit
full-write
gettext-h
+ignore-value
open
safe-read
unistd
--
1.7.4.1.21.g4cc62
