[COMMITTED 2.26 1/3] <array_length.h>: New array_length and array_end macros

[Aurelien Jarno]

From: Florian Weimer <fweimer@redhat.com>

(cherry picked from commit c94a5688fb1228a862b2d4a3f1239cdc0e3349e5)
---
 ChangeLog              |  5 +++++
 include/array_length.h | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 include/array_length.h

diff --git a/ChangeLog b/ChangeLog
index 1bf692af23..90ea98550f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-11-02  Florian Weimer  <fweimer@redhat.com>
+
+	Add array_length and array_end macros.
+	* include/array_length.h: New file.
+
 2017-10-27  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/i386/fpu/libm-test-ulps: Regenerated for GCC 7 with
diff --git a/include/array_length.h b/include/array_length.h
new file mode 100644
index 0000000000..cb4a8b2a56
--- /dev/null
+++ b/include/array_length.h
@@ -0,0 +1,36 @@
+/* The array_length and array_end macros.
+   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/>.  */
+
+#ifndef _ARRAY_LENGTH_H
+#define _ARRAY_LENGTH_H
+
+/* array_length (VAR) is the number of elements in the array VAR.  VAR
+   must evaluate to an array, not a pointer.  */
+#define array_length(var)                                               \
+  __extension__ ({                                                      \
+    _Static_assert (!__builtin_types_compatible_p                       \
+                    (__typeof (var), __typeof (&(var)[0])),             \
+                    "argument must be an array");                       \
+    sizeof (var) / sizeof ((var)[0]);                                   \
+  })
+
+/* array_end (VAR) is a pointer one past the end of the array VAR.
+   VAR must evaluate to an array, not a pointer.  */
+#define array_end(var) (&(var)[array_length (var)])
+
+#endif /* _ARRAY_LENGTH_H */
-- 
2.15.1