maint: avoid warnings due to attribute warn_unused_result

Now that a (void) cast no longer suffices to ignore warnings from gcc
about uses of functions marked with the warn_unused_result attribute,
we need an alternative.  For the record, here's one of the ignorable
warnings: "copy.c:233: warning: ignoring return value of 'fchown',
declared with attribute warn_unused_result"
* bootstrap.conf (gnulib_modules): Import ignore-value.
* src/copy.c: Include "ignore-value.h".
(set_owner): Use ignore_value in place of "(void)" casts,
to ignore lchown and fchown failures.
* src/cp.c (re_protect): Likewise, to ignore lchown failure.
* src/remove.c (preprocess_dir): Remove unnecessary "(void)" cast.

3 files changed, 6 insertions, 4 deletions

diff --git a/src/copy.c b/src/copy.c
index 82c6978e4..5a584752d 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -44,6 +44,7 @@
 #include "full-write.h"
 #include "hash.h"
 #include "hash-triple.h"
+#include "ignore-value.h"
 #include "lchmod.h"
 #include "quote.h"
 #include "same.h"
@@ -230,7 +231,7 @@ set_owner (const struct cp_options *x, char const *dst_name, int dest_desc,
 	  /* We've failed to set *both*.  Now, try to set just the group
 	     ID, but ignore any failure here, and don't change errno.  */
           int saved_errno = errno;
-          (void) fchown (dest_desc, -1, gid);
+          ignore_value (fchown (dest_desc, -1, gid));
           errno = saved_errno;
         }
     }
@@ -243,7 +244,7 @@ set_owner (const struct cp_options *x, char const *dst_name, int dest_desc,
 	  /* We've failed to set *both*.  Now, try to set just the group
 	     ID, but ignore any failure here, and don't change errno.  */
           int saved_errno = errno;
-          (void) lchown (dst_name, -1, gid);
+          ignore_value (lchown (dst_name, -1, gid));
           errno = saved_errno;
         }
     }
diff --git a/src/cp.c b/src/cp.c
index 77d47027d..58c9c0953 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -29,6 +29,7 @@
 #include "cp-hash.h"
 #include "error.h"
 #include "filenamecat.h"
+#include "ignore-value.h"
 #include "lchmod.h"
 #include "quote.h"
 #include "stat-time.h"
@@ -326,7 +327,7 @@ re_protect (char const *const_dst_name, size_t src_offset,
                 }
               /* Failing to preserve ownership is OK. Still, try to preserve
                  the group, but ignore the possible error. */
-              (void) lchown (dst_name, -1, p->st.st_gid);
+              ignore_value (lchown (dst_name, -1, p->st.st_gid));
             }
 	}
 
diff --git a/src/remove.c b/src/remove.c
index 2e342c092..e92f78caf 100644
--- a/src/remove.c
+++ b/src/remove.c
@@ -1423,7 +1423,7 @@ preprocess_dir (DIR **dirp, struct rm_options const *x)
   for (size_t i = 0; i < n; i++)
     {
       /* ignore failure */
-      (void) unlinkat (dir_fd, vv[i]->name, 0);
+      unlinkat (dir_fd, vv[i]->name, 0);
     }
 
  cleanup: