[2.26 COMMITTED] sysconf: Fix missing definition of UIO_MAXIOV on Linux [BZ #22321]

[Florian Weimer]

After commit 37f802f86400684c8d13403958b2c598721d6360 (Remove
__need_IOV_MAX and __need_FOPEN_MAX), UIO_MAXIOV is no longer supplied
(indirectly) through <bits/stdio_lim.h>, so sysdeps/posix/sysconf.c no
longer sees the definition.

(cherry picked from commit 63b4baa44e8d22501c433c4093aa3310f91b6aa2)

2017-10-20  Florian Weimer  <fweimer@redhat.com>

	[BZ #22321]
	sysconf: Fix missing definition of UIO_MAXIOV on Linux.
	* sysdeps/posix/sysconf.c: Include <sys/uio.h>.
	* sysdeps/unix/sysv/linux/Makefile (tests): Add tst-sysconf-iov_max.
	(tst-sysconf-iov_max): Link with tst-sysconf-iov_max-uapi.o.
	* sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c: New file.
	* sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c: Likewise.

diff --git a/NEWS b/NEWS
index 9cb8f00529..e5ac109a63 100644
--- a/NEWS
+++ b/NEWS
@@ -38,6 +38,7 @@ The following bugs are resolved with this release:
   [22146] Let fpclassify use the builtin when optimizing for size in C++ mode
   [22225] math: nearbyint arithmetic moved before feholdexcept
   [22235] Add C++ versions of iscanonical for ldbl-96 and ldbl-128ibm
+  [22321] sysconf: Fix missing definition of UIO_MAXIOV on Linux
 
 Version 2.26
 
diff --git a/sysdeps/posix/sysconf.c b/sysdeps/posix/sysconf.c
index a95e1b3f05..254f87c437 100644
--- a/sysdeps/posix/sysconf.c
+++ b/sysdeps/posix/sysconf.c
@@ -29,6 +29,7 @@
 #include <sys/stat.h>
 #include <sys/sysinfo.h>
 #include <sys/types.h>
+#include <sys/uio.h>
 #include <regex.h>
 
 #define NEED_SPEC_ARRAY 0
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 9d6a2de870..5dce300f7f 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -50,7 +50,7 @@ sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
 		  bits/siginfo-arch.h bits/siginfo-consts-arch.h
 
 tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
-	 tst-quota tst-sync_file_range test-errno-linux
+	 tst-quota tst-sync_file_range test-errno-linux tst-sysconf-iov_max
 
 # Generate the list of SYS_* macros for the system calls (__NR_* macros).
 
@@ -120,7 +120,11 @@ ifndef no_deps
 -include $(objpfx)bits/syscall.d
 endif
 generated += bits/syscall.h bits/syscall.d
-endif
+
+# Separate object file for access to the constant from the UAPI header.
+$(objpfx)tst-sysconf-iov_max: $(objpfx)tst-sysconf-iov_max-uapi.o
+
+endif # $(subdir) == misc
 
 ifeq ($(subdir),time)
 sysdep_headers += sys/timex.h bits/timex.h
diff --git a/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c
new file mode 100644
index 0000000000..1240b846e6
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c
@@ -0,0 +1,27 @@
+/* Check IOV_MAX definition: Helper function to capture UAPI header value.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Use a separate function to avoid header compatibility issues.  */
+
+#include <linux/uio.h>
+
+long
+uio_maxiov_value (void)
+{
+  return UIO_MAXIOV;
+}
diff --git a/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c
new file mode 100644
index 0000000000..dfdf3da484
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c
@@ -0,0 +1,40 @@
+/* Check IOV_MAX definition for consistency (bug 22321).
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Defined in tst-sysconf-iov_max-uapi.c.  */
+long uio_maxiov_value (void);
+
+
+#include <limits.h>
+#include <support/check.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+static int
+do_test (void)
+{
+  TEST_VERIFY (_XOPEN_IOV_MAX == 16); /* Value required by POSIX.  */
+  TEST_VERIFY (uio_maxiov_value () >= _XOPEN_IOV_MAX);
+  TEST_VERIFY (IOV_MAX == uio_maxiov_value ());
+  TEST_VERIFY (UIO_MAXIOV == uio_maxiov_value ());
+  TEST_VERIFY (sysconf (_SC_UIO_MAXIOV) == uio_maxiov_value ());
+  TEST_VERIFY (sysconf (_SC_IOV_MAX) == uio_maxiov_value ());
+  return 0;
+}
+
+#include <support/test-driver.c>