misc/sys/select.h (__FD_MASK): Avoid signed integer overflow.

Shifting into the sign position is currently supported as a GCC
extension, but explicitly subjected to future changes.  Computation
in the unsigned type followed by a cast to the signed type is a GCC
extension that will be available forever.

ChangeLog

@@ -1,3 +1,8 @@
+2014-02-25  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #15347]
+	* misc/sys/select.h (__FD_MASK): Avoid signed integer overflow.
+
 2014-02-25  Will Newton  <will.newton@linaro.org>
 
 	* sysdeps/arm/__longjmp.S: Include stap-probe.h.

NEWS

@@ -9,7 +9,7 @@ Version 2.20
 
 * The following bugs are resolved with this release:
 
-  15804, 15894, 16447, 16545, 16574, 16600, 16609, 16610, 16611.
+  15347, 15804, 15894, 16447, 16545, 16574, 16600, 16609, 16610, 16611.
 
 * The am33 port, which had not worked for several years, has been removed
   from ports.

misc/sys/select.h

@@ -58,7 +58,7 @@ typedef long int __fd_mask;
 /* It's easier to assume 8-bit bytes than to get CHAR_BIT.  */
 #define __NFDBITS	(8 * (int) sizeof (__fd_mask))
 #define	__FD_ELT(d)	((d) / __NFDBITS)
-#define	__FD_MASK(d)	((__fd_mask) 1 << ((d) % __NFDBITS))
+#define	__FD_MASK(d)	((__fd_mask) (1UL << ((d) % __NFDBITS)))
 
 /* fd_set for select and pselect.  */
 typedef struct