Adding upstream version 2.13.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

gl/lib/sig-handler.h

@@ -0,0 +1,53 @@
+/* Convenience declarations when working with <signal.h>.
+
+   Copyright (C) 2008-2024 Free Software Foundation, Inc.
+
+   This file 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.
+
+   This file 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 this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _GL_SIG_HANDLER_H
+#define _GL_SIG_HANDLER_H
+
+/* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE, _GL_ATTRIBUTE_PURE.  */
+#if !_GL_CONFIG_H_INCLUDED
+ #error "Please include config.h first."
+#endif
+
+#include <signal.h>
+
+_GL_INLINE_HEADER_BEGIN
+#ifndef SIG_HANDLER_INLINE
+# define SIG_HANDLER_INLINE _GL_INLINE
+#endif
+
+/* 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.  */
+SIG_HANDLER_INLINE sa_handler_t _GL_ATTRIBUTE_PURE
+get_handler (struct sigaction const *a)
+{
+  /* 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.  In
+     this case, this implementation relies on the fact that the two
+     are aliases, and simply returns sa_handler.  */
+  return a->sa_handler;
+}
+
+_GL_INLINE_HEADER_END
+
+#endif /* _GL_SIG_HANDLER_H */