[PATCH] Fix build issue due to Introduce nat/linux-namespaces.[ch] patch

[Peter Bergner <bergner@vnet.ibm.com>]

I have a toolchain that dies building gdb with the following error:

/home/bergner/binutils/binutils-gdb/gdb/nat/linux-namespaces.c:39:1: error: static declaration of ‘setns’ follows non-static declaration
 setns (int fd, int nstype)
 ^
In file included from /opt/at7.0/include/sched.h:41:0,
                 from /home/bergner/binutils/binutils-gdb/gdb/nat/linux-namespaces.c:30:
/opt/at7.0/include/bits/sched.h:91:12: note: previous declaration of ‘setns’ was here
 extern int setns (int __fd, int __nstype) __THROW;
            ^
make[2]: *** [linux-namespaces.o] Error 1

My configure doesn't define HAVE_SETNS because my glibc defines __stub_setns,
so nat/linux-namespaces.c defines its own setns routine.  However, my glibc
also has its sched.h with a extern prototype for setns, which conflicts with
this static version linux-namespaces.c is creating, so we get the error above.
How about the following patch to work around the error?  I can confirm that
it fixes the problem on my multiple systems that do and do not have setns.

Ok for trunk?

Peter

	* nat/linux-namespaces.c (setns): Rename from this ...
	(do_setns): ... to this.  Support calling setns if it exists.
	(mnsh_handle_setns): Call do_setns.

diff --git a/gdb/nat/linux-namespaces.c b/gdb/nat/linux-namespaces.c
index a7a3e4d..c2f0d2e 100644
--- a/gdb/nat/linux-namespaces.c
+++ b/gdb/nat/linux-namespaces.c
@@ -34,18 +34,20 @@ int debug_linux_namespaces;

 /* Handle systems without setns.  */

-#ifndef HAVE_SETNS
-static int
-setns (int fd, int nstype)
+static inline int
+do_setns (int fd, int nstype)
 {
-#ifdef __NR_setns
-  return syscall (__NR_setns, fd, nstype);
+#ifdef HAVE_SETNS
+  return setns (fd, nstype);
 #else
+# ifdef __NR_setns
+  return syscall (__NR_setns, fd, nstype);
+# else
   errno = ENOSYS;
   return -1;
+# endif
 #endif
 }
-#endif

 /* Handle systems without MSG_CMSG_CLOEXEC.  */

@@ -495,7 +497,7 @@ mnsh_recv_message (int sock, enum mnsh_msg_type *type,
 static ssize_t
 mnsh_handle_setns (int sock, int fd, int nstype)
 {
-  int result = setns (fd, nstype);
+  int result = do_setns (fd, nstype);

   return mnsh_return_int (sock, result, errno);
 }