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+/* Convenience declarations when working with <signal.h>.
+
+ Copyright (C) 2008-2011 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef _GL_SIG_HANDLER_H
+#define _GL_SIG_HANDLER_H
+
+#include <signal.h>
+
+/* Convenience type when working with signal handlers. */
+typedef void (*sa_handler_t) (int);
+
+/* Return the handler of a signal, as a sa_handler_t value regardless
+ of its true type. The resulting function can be compared to
+ special values like SIG_IGN but it is not portable to call it. */
+static inline sa_handler_t
+get_handler (struct sigaction const *a)
+{
+#ifdef SA_SIGINFO
+ /* POSIX says that special values like SIG_IGN can only occur when
+ action.sa_flags does not contain SA_SIGINFO. But in Linux 2.4,
+ for example, sa_sigaction and sa_handler are aliases and a signal
+ is ignored if sa_sigaction (after casting) equals SIG_IGN. So
+ use (and cast) sa_sigaction in that case. */
+ if (a->sa_flags & SA_SIGINFO)
+ return (sa_handler_t) a->sa_sigaction;
+#endif
+ return a->sa_handler;
+}
+
+#endif /* _GL_SIG_HANDLER_H */