--- /dev/null
+/* POSIX compatible signal blocking.
+ Copyright (C) 2006-2018 Free Software Foundation, Inc.
+ Written by Bruno Haible <bruno@clisp.org>, 2006.
+
+ 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 <https://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include <signal.h>
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#if HAVE_MSVC_INVALID_PARAMETER_HANDLER
+# include "msvc-inval.h"
+#endif
+
+/* We assume that a platform without POSIX signal blocking functions
+ also does not have the POSIX sigaction() function, only the
+ signal() function. We also assume signal() has SysV semantics,
+ where any handler is uninstalled prior to being invoked. This is
+ true for native Windows platforms. */
+
+/* We use raw signal(), but also provide a wrapper rpl_signal() so
+ that applications can query or change a blocked signal. */
+#undef signal
+
+/* Provide invalid signal numbers as fallbacks if the uncatchable
+ signals are not defined. */
+#ifndef SIGKILL
+# define SIGKILL (-1)
+#endif
+#ifndef SIGSTOP
+# define SIGSTOP (-1)
+#endif
+
+/* On native Windows, as of 2008, the signal SIGABRT_COMPAT is an alias
+ for the signal SIGABRT. Only one signal handler is stored for both
+ SIGABRT and SIGABRT_COMPAT. SIGABRT_COMPAT is not a signal of its own. */
+#if defined _WIN32 && ! defined __CYGWIN__
+# undef SIGABRT_COMPAT
+# define SIGABRT_COMPAT 6
+#endif
+#ifdef SIGABRT_COMPAT
+# define SIGABRT_COMPAT_MASK (1U << SIGABRT_COMPAT)
+#else
+# define SIGABRT_COMPAT_MASK 0
+#endif
+
+typedef void (*handler_t) (int);
+
+#if HAVE_MSVC_INVALID_PARAMETER_HANDLER
+static handler_t
+signal_nothrow (int sig, handler_t handler)
+{
+ handler_t result;
+
+ TRY_MSVC_INVAL
+ {
+ result = signal (sig, handler);
+ }
+ CATCH_MSVC_INVAL
+ {
+ result = SIG_ERR;
+ errno = EINVAL;
+ }
+ DONE_MSVC_INVAL;
+
+ return result;
+}
+# define signal signal_nothrow
+#endif
+
+/* Handling of gnulib defined signals. */
+
+#if GNULIB_defined_SIGPIPE
+static handler_t SIGPIPE_handler = SIG_DFL;
+#endif
+
+#if GNULIB_defined_SIGPIPE
+static handler_t
+ext_signal (int sig, handler_t handler)
+{
+ switch (sig)
+ {
+ case SIGPIPE:
+ {
+ handler_t old_handler = SIGPIPE_handler;
+ SIGPIPE_handler = handler;
+ return old_handler;
+ }
+ default: /* System defined signal */
+ return signal (sig, handler);
+ }
+}
+# undef signal
+# define signal ext_signal
+#endif
+
+int
+sigismember (const sigset_t *set, int sig)
+{
+ if (sig >= 0 && sig < NSIG)
+ {
+ #ifdef SIGABRT_COMPAT
+ if (sig == SIGABRT_COMPAT)
+ sig = SIGABRT;
+ #endif
+
+ return (*set >> sig) & 1;
+ }
+ else
+ return 0;
+}
+
+int
+sigemptyset (sigset_t *set)
+{
+ *set = 0;
+ return 0;
+}
+
+int
+sigaddset (sigset_t *set, int sig)
+{
+ if (sig >= 0 && sig < NSIG)
+ {
+ #ifdef SIGABRT_COMPAT
+ if (sig == SIGABRT_COMPAT)
+ sig = SIGABRT;
+ #endif
+
+ *set |= 1U << sig;
+ return 0;
+ }
+ else
+ {
+ errno = EINVAL;
+ return -1;
+ }
+}
+
+int
+sigdelset (sigset_t *set, int sig)
+{
+ if (sig >= 0 && sig < NSIG)
+ {
+ #ifdef SIGABRT_COMPAT
+ if (sig == SIGABRT_COMPAT)
+ sig = SIGABRT;
+ #endif
+
+ *set &= ~(1U << sig);
+ return 0;
+ }
+ else
+ {
+ errno = EINVAL;
+ return -1;
+ }
+}
+
+
+int
+sigfillset (sigset_t *set)
+{
+ *set = ((2U << (NSIG - 1)) - 1) & ~ SIGABRT_COMPAT_MASK;
+ return 0;
+}
+
+/* Set of currently blocked signals. */
+static volatile sigset_t blocked_set /* = 0 */;
+
+/* Set of currently blocked and pending signals. */
+static volatile sig_atomic_t pending_array[NSIG] /* = { 0 } */;
+
+/* Signal handler that is installed for blocked signals. */
+static void
+blocked_handler (int sig)
+{
+ /* Reinstall the handler, in case the signal occurs multiple times
+ while blocked. There is an inherent race where an asynchronous
+ signal in between when the kernel uninstalled the handler and
+ when we reinstall it will trigger the default handler; oh
+ well. */
+ signal (sig, blocked_handler);
+ if (sig >= 0 && sig < NSIG)
+ pending_array[sig] = 1;
+}
+
+int
+sigpending (sigset_t *set)
+{
+ sigset_t pending = 0;
+ int sig;
+
+ for (sig = 0; sig < NSIG; sig++)
+ if (pending_array[sig])
+ pending |= 1U << sig;
+ *set = pending;
+ return 0;
+}
+
+/* The previous signal handlers.
+ Only the array elements corresponding to blocked signals are relevant. */
+static volatile handler_t old_handlers[NSIG];
+
+int
+sigprocmask (int operation, const sigset_t *set, sigset_t *old_set)
+{
+ if (old_set != NULL)
+ *old_set = blocked_set;
+
+ if (set != NULL)
+ {
+ sigset_t new_blocked_set;
+ sigset_t to_unblock;
+ sigset_t to_block;
+
+ switch (operation)
+ {
+ case SIG_BLOCK:
+ new_blocked_set = blocked_set | *set;
+ break;
+ case SIG_SETMASK:
+ new_blocked_set = *set;
+ break;
+ case SIG_UNBLOCK:
+ new_blocked_set = blocked_set & ~*set;
+ break;
+ default:
+ errno = EINVAL;
+ return -1;
+ }
+ to_unblock = blocked_set & ~new_blocked_set;
+ to_block = new_blocked_set & ~blocked_set;
+
+ if (to_block != 0)
+ {
+ int sig;
+
+ for (sig = 0; sig < NSIG; sig++)
+ if ((to_block >> sig) & 1)
+ {
+ pending_array[sig] = 0;
+ if ((old_handlers[sig] = signal (sig, blocked_handler)) != SIG_ERR)
+ blocked_set |= 1U << sig;
+ }
+ }
+
+ if (to_unblock != 0)
+ {
+ sig_atomic_t received[NSIG];
+ int sig;
+
+ for (sig = 0; sig < NSIG; sig++)
+ if ((to_unblock >> sig) & 1)
+ {
+ if (signal (sig, old_handlers[sig]) != blocked_handler)
+ /* The application changed a signal handler while the signal
+ was blocked, bypassing our rpl_signal replacement.
+ We don't support this. */
+ abort ();
+ received[sig] = pending_array[sig];
+ blocked_set &= ~(1U << sig);
+ pending_array[sig] = 0;
+ }
+ else
+ received[sig] = 0;
+
+ for (sig = 0; sig < NSIG; sig++)
+ if (received[sig])
+ raise (sig);
+ }
+ }
+ return 0;
+}
+
+/* Install the handler FUNC for signal SIG, and return the previous
+ handler. */
+handler_t
+rpl_signal (int sig, handler_t handler)
+{
+ /* We must provide a wrapper, so that a user can query what handler
+ they installed even if that signal is currently blocked. */
+ if (sig >= 0 && sig < NSIG && sig != SIGKILL && sig != SIGSTOP
+ && handler != SIG_ERR)
+ {
+ #ifdef SIGABRT_COMPAT
+ if (sig == SIGABRT_COMPAT)
+ sig = SIGABRT;
+ #endif
+
+ if (blocked_set & (1U << sig))
+ {
+ /* POSIX states that sigprocmask and signal are both
+ async-signal-safe. This is not true of our
+ implementation - there is a slight data race where an
+ asynchronous interrupt on signal A can occur after we
+ install blocked_handler but before we have updated
+ old_handlers for signal B, such that handler A can see
+ stale information if it calls signal(B). Oh well -
+ signal handlers really shouldn't try to manipulate the
+ installed handlers of unrelated signals. */
+ handler_t result = old_handlers[sig];
+ old_handlers[sig] = handler;
+ return result;
+ }
+ else
+ return signal (sig, handler);
+ }
+ else
+ {
+ errno = EINVAL;
+ return SIG_ERR;
+ }
+}
+
+#if GNULIB_defined_SIGPIPE
+/* Raise the signal SIGPIPE. */
+int
+_gl_raise_SIGPIPE (void)
+{
+ if (blocked_set & (1U << SIGPIPE))
+ pending_array[SIGPIPE] = 1;
+ else
+ {
+ handler_t handler = SIGPIPE_handler;
+ if (handler == SIG_DFL)
+ exit (128 + SIGPIPE);
+ else if (handler != SIG_IGN)
+ (*handler) (SIGPIPE);
+ }
+ return 0;
+}
+#endif
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