Factor out shared definitions from bits/signum.h.

Many of the things defined by bits/signum.h are invariant across all
supported operating systems.  This patch factors out all of them to a
new header bits/signum-generic.h, which each bits/signum.h will include
and then override whichever things need adjustment.  Normally that will
mean, at most, adding or changing a few signal numbers.

A user-visible side effect is that the obsolete signal constant SIGUNUSED
(which is an alias for SIGSYS on all platforms that define it) is no
longer exposed by any version of bits/signum.h.

A side effect only relevant to glibc hackers is that _NSIG is now defined
in terms of __SIGRTMAX, instead of the other way around.  This is because
__SIGRTMAX varies from platform to platform, but _NSIG==__SIGRTMAX+1 is
true universally.  If your platform doesn't support realtime signals,
leave __SIGRTMAX equal to __SIGRTMIN.

I also added a Linux-specific test to make sure that our signal constants
match the ones in <asm/signal.h>, since we can't use that header (it's
not even vaguely namespace-clean).

	* bits/signum-generic.h: Renamed from bits/signum.h.
	Add proper multiple include guard and misuse check.
	Define __SIGRTMIN = __SIGRTMAX = 32, and define _NSIG = __SIGRTMAX+1.
	Move definition of SIGIO to "archaic names for compatibility" section.
	* bits/signum.h: New file which just includes bits/signum-generic.h.
	* sysdeps/unix/bsd/bits/signum.h
	* sysdeps/unix/sysv/linux/bits/signum.h
	* sysdeps/unix/sysv/linux/alpha/bits/signum.h
	* sysdeps/unix/sysv/linux/hppa/bits/signum.h
	* sysdeps/unix/sysv/linux/mips/bits/signum.h
	* sysdeps/unix/sysv/linux/sparc/bits/signum.h
	Just include <bits/signum-generic.h> and then add or adjust
	signal constants.  Do not define SIGUNUSED, SIGRTMIN, or SIGRTMAX.

	* signal/Makefile: Install bits/signum-generic.h.
	* signal/signal.h: Define SIGRTMIN and SIGRTMAX here.

	* sysdeps/generic/siglist.h: SIGSYS and SIGWINCH are
	universal.  Prefer SIGPOLL to SIGIO. Simplify #ifdeffage.

	* sysdeps/unix/sysv/linux/tst-signal-numbers.sh: New test.
	* sysdeps/unix/sysv/linux/Makefile: Run it.

2 files changed, 112 insertions, 62 deletions

diff --git a/bits/signum-generic.h b/bits/signum-generic.h
new file mode 100644
index 0000000000..5a5683e753
--- /dev/null
+++ b/bits/signum-generic.h
@@ -0,0 +1,102 @@
+/* Signal number constants.  Generic template.
+   Copyright (C) 1991-2017 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	_BITS_SIGNUM_GENERIC_H
+#define _BITS_SIGNUM_GENERIC_H 1
+
+#ifndef _SIGNAL_H
+#error "Never include <bits/signum-generic.h> directly; use <signal.h> instead."
+#endif
+
+/* Fake signal functions.  */
+
+#define	SIG_ERR	 ((__sighandler_t) -1)	/* Error return.  */
+#define	SIG_DFL	 ((__sighandler_t)  0)	/* Default action.  */
+#define	SIG_IGN	 ((__sighandler_t)  1)	/* Ignore signal.  */
+
+#ifdef __USE_XOPEN
+# define SIG_HOLD ((__sighandler_t) 2)	/* Add signal to hold mask.  */
+#endif
+
+/* We define here all the signal names listed in POSIX (1003.1-2008);
+   as of 1003.1-2013, no additional signals have been added by POSIX.
+   We also define here signal names that historically exist in every
+   real-world POSIX variant (e.g. SIGWINCH).
+
+   Signals in the 1-15 range are defined with their historical numbers.
+   For other signals, we use the BSD numbers.
+   There are two unallocated signal numbers in the 1-31 range: 7 and 29.
+   Signal number 0 is reserved for use as kill(pid, 0), to test whether
+   a process exists without sending it a signal.  */
+
+/* ISO C99 signals.  */
+#define	SIGINT		2	/* Interactive attention signal.  */
+#define	SIGILL		4	/* Illegal instruction.  */
+#define	SIGABRT		6	/* Abnormal termination.  */
+#define	SIGFPE		8	/* Erroneous arithmetic operation.  */
+#define	SIGSEGV		11	/* Invalid access to storage.  */
+#define	SIGTERM		15	/* Termination request.  */
+
+/* Historical signals specified by POSIX. */
+#define	SIGHUP		1	/* Hangup.  */
+#define	SIGQUIT		3	/* Quit.  */
+#define	SIGTRAP		5	/* Trace/breakpoint trap.  */
+#define	SIGKILL		9	/* Killed.  */
+#define SIGBUS		10	/* Bus error.  */
+#define	SIGSYS		12	/* Bad system call.  */
+#define	SIGPIPE		13	/* Broken pipe.  */
+#define	SIGALRM		14	/* Alarm clock.  */
+
+/* New(er) POSIX signals (1003.1-2008, 1003.1-2013).  */
+#define	SIGURG		16	/* Urgent data is available at a socket.  */
+#define	SIGSTOP		17	/* Stop, unblockable.  */
+#define	SIGTSTP		18	/* Keyboard stop.  */
+#define	SIGCONT		19	/* Continue.  */
+#define	SIGCHLD		20	/* Child terminated or stopped.  */
+#define	SIGTTIN		21	/* Background read from control terminal.  */
+#define	SIGTTOU		22	/* Background write to control terminal.  */
+#define	SIGPOLL		23	/* Pollable event occurred (System V).  */
+#define	SIGXCPU		24	/* CPU time limit exceeded.  */
+#define	SIGXFSZ		25	/* File size limit exceeded.  */
+#define	SIGVTALRM	26	/* Virtual timer expired.  */
+#define	SIGPROF		27	/* Profiling timer expired.  */
+#define	SIGUSR1		30	/* User-defined signal 1.  */
+#define	SIGUSR2		31	/* User-defined signal 2.  */
+
+/* Nonstandard signals found in all modern POSIX systems
+   (including both BSD and Linux).  */
+#define	SIGWINCH	28	/* Window size change (4.3 BSD, Sun).  */
+
+/* Archaic names for compatibility.  */
+#define	SIGIO		SIGPOLL	/* I/O now possible (4.2 BSD).  */
+#define	SIGIOT		SIGABRT	/* IOT instruction, abort() on a PDP-11.  */
+#define	SIGCLD		SIGCHLD	/* Old System V name */
+
+/* Not all systems support real-time signals.  bits/signum.h indicates
+   that they are supported by overriding __SIGRTMAX to a value greater
+   than __SIGRTMIN.  These constants give the kernel-level hard limits,
+   but some real-time signals may be used internally by glibc.  Do not
+   use these constants in application code; use SIGRTMIN and SIGRTMAX
+   (defined in signal.h) instead.  */
+#define __SIGRTMIN	32
+#define __SIGRTMAX	__SIGRTMIN
+
+/* Biggest signal number + 1 (including real-time signals).  */
+#define _NSIG		(__SIGRTMAX + 1)
+
+#endif /* bits/signum-generic.h.  */
diff --git a/bits/signum.h b/bits/signum.h
index cfbc7ac8bb..8d6d03c918 100644
--- a/bits/signum.h
+++ b/bits/signum.h
@@ -1,5 +1,5 @@
 /* Signal number constants.  Generic version.
-   Copyright (C) 1991-2017 Free Software Foundation, Inc.
+   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
@@ -16,69 +16,17 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#ifdef	_SIGNAL_H
+#ifndef _BITS_SIGNUM_H
+#define _BITS_SIGNUM_H 1
 
-/* Fake signal functions.  */
-
-#define	SIG_ERR	 ((__sighandler_t) -1)	/* Error return.  */
-#define	SIG_DFL	 ((__sighandler_t)  0)	/* Default action.  */
-#define	SIG_IGN	 ((__sighandler_t)  1)	/* Ignore signal.  */
-
-#ifdef __USE_XOPEN
-# define SIG_HOLD ((__sighandler_t)  2)	/* Add signal to hold mask.  */
+#ifndef _SIGNAL_H
+#error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
-/* We define here all the signal names listed in POSIX (1003.1-2008);
-   as of 1003.1-2013, no additional signals have been added by POSIX.
-   We also define here signal names that historically exist in every
-   real-world POSIX variant (e.g. SIGWINCH).
-
-   Signals in the 1-15 range are defined with their historical numbers.
-   For other signals, we use the BSD numbers.  */
-
-/* ISO C99 signals.  */
-#define	SIGINT		2	/* Interactive attention signal.  */
-#define	SIGILL		4	/* Illegal instruction.  */
-#define	SIGABRT		6	/* Abnormal termination.  */
-#define	SIGFPE		8	/* Erroneous arithmetic operation.  */
-#define	SIGSEGV		11	/* Invalid access to storage.  */
-#define	SIGTERM		15	/* Termination request.  */
-
-/* Historical signals specified by POSIX. */
-#define	SIGHUP		1	/* Hangup.  */
-#define	SIGQUIT		3	/* Quit.  */
-#define	SIGTRAP		5	/* Trace/breakpoint trap.  */
-#define	SIGKILL		9	/* Killed.  */
-#define SIGBUS		10	/* Bus error.  */
-#define	SIGSYS		12	/* Bad system call.  */
-#define	SIGPIPE		13	/* Broken pipe.  */
-#define	SIGALRM		14	/* Alarm clock.  */
-
-/* New(er) POSIX signals (1003.1-2008, 1003.1-2013).  */
-#define	SIGURG		16 /* High bandwidth data is available at a socket.  */
-#define	SIGSTOP		17	/* Stopped (signal).  */
-#define	SIGTSTP		18	/* Stopped.  */
-#define	SIGCONT		19	/* Continued.  */
-#define	SIGCHLD		20	/* Child terminated or stopped.  */
-#define	SIGTTIN		21	/* Background read from control terminal.  */
-#define	SIGTTOU		22	/* Background write to control terminal.  */
-#define	SIGPOLL 	23	/* Pollable event occurred (System V).  */
-#define	SIGIO		SIGPOLL /* I/O now possible (4.2 BSD).  */
-#define	SIGXCPU		24	/* CPU time limit exceeded.  */
-#define	SIGXFSZ		25	/* File size limit exceeded.  */
-#define	SIGVTALRM	26	/* Virtual timer expired.  */
-#define	SIGPROF		27	/* Profiling timer expired.  */
-#define	SIGUSR1		30	/* User-defined signal 1.  */
-#define	SIGUSR2		31	/* User-defined signal 2.  */
-
-/* Nonstandard signals found in all modern POSIX systems
-   (including both BSD and Linux).  */
-#define	SIGWINCH	28	/* Window size change (4.3 BSD, Sun).  */
-
-#define	_NSIG		32
+#include <bits/signum-generic.h>
 
-/* Archaic names for compatibility. */
-#define	SIGIOT		SIGABRT	/* IOT instruction, abort() on a PDP-11.  */
-#define	SIGCLD		SIGCHLD	/* Old System V name */
+/* This operating system does not need to override any of the generic
+   signal number assignments in bits/signum-generic.h, nor to add any
+   additional signal constants.  */
 
-#endif	/* <signal.h> included.  */
+#endif /* bits/signum.h.  */