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///////////////////////////////////////////////////////////////////////////////
//
/// \file signals.c
/// \brief Handling signals to abort operation
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include "private.h"
volatile sig_atomic_t user_abort = false;
#if !(defined(_WIN32) && !defined(__CYGWIN__))
/// If we were interrupted by a signal, we store the signal number so that
/// we can raise that signal to kill the program when all cleanups have
/// been done.
static volatile sig_atomic_t exit_signal = 0;
/// Mask of signals for which we have established a signal handler to set
/// user_abort to true.
static sigset_t hooked_signals;
/// True once signals_init() has finished. This is used to skip blocking
/// signals (with uninitialized hooked_signals) if signals_block() and
/// signals_unblock() are called before signals_init() has been called.
static bool signals_are_initialized = false;
/// signals_block() and signals_unblock() can be called recursively.
static size_t signals_block_count = 0;
static void
signal_handler(int sig)
{
exit_signal = sig;
user_abort = true;
#ifndef TUKLIB_DOSLIKE
io_write_to_user_abort_pipe();
#endif
return;
}
extern void
signals_init(void)
{
// List of signals for which we establish the signal handler.
static const int sigs[] = {
SIGINT,
SIGTERM,
#ifdef SIGHUP
SIGHUP,
#endif
#ifdef SIGPIPE
SIGPIPE,
#endif
#ifdef SIGXCPU
SIGXCPU,
#endif
#ifdef SIGXFSZ
SIGXFSZ,
#endif
};
// Mask of the signals for which we have established a signal handler.
sigemptyset(&hooked_signals);
for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i)
sigaddset(&hooked_signals, sigs[i]);
#ifdef SIGALRM
// Add also the signals from message.c to hooked_signals.
for (size_t i = 0; message_progress_sigs[i] != 0; ++i)
sigaddset(&hooked_signals, message_progress_sigs[i]);
#endif
// Using "my_sa" because "sa" may conflict with a sockaddr variable
// from system headers on Solaris.
struct sigaction my_sa;
// All the signals that we handle we also blocked while the signal
// handler runs.
my_sa.sa_mask = hooked_signals;
// Don't set SA_RESTART, because we want EINTR so that we can check
// for user_abort and cleanup before exiting. We block the signals
// for which we have established a handler when we don't want EINTR.
my_sa.sa_flags = 0;
my_sa.sa_handler = &signal_handler;
for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i) {
// If the parent process has left some signals ignored,
// we don't unignore them.
struct sigaction old;
if (sigaction(sigs[i], NULL, &old) == 0
&& old.sa_handler == SIG_IGN)
continue;
// Establish the signal handler.
if (sigaction(sigs[i], &my_sa, NULL))
message_signal_handler();
}
signals_are_initialized = true;
return;
}
#ifndef __VMS
extern void
signals_block(void)
{
if (signals_are_initialized) {
if (signals_block_count++ == 0) {
const int saved_errno = errno;
mythread_sigmask(SIG_BLOCK, &hooked_signals, NULL);
errno = saved_errno;
}
}
return;
}
extern void
signals_unblock(void)
{
if (signals_are_initialized) {
assert(signals_block_count > 0);
if (--signals_block_count == 0) {
const int saved_errno = errno;
mythread_sigmask(SIG_UNBLOCK, &hooked_signals, NULL);
errno = saved_errno;
}
}
return;
}
#endif
extern void
signals_exit(void)
{
const int sig = (int)exit_signal;
if (sig != 0) {
#if defined(TUKLIB_DOSLIKE) || defined(__VMS)
// Don't raise(), set only exit status. This avoids
// printing unwanted message about SIGINT when the user
// presses C-c.
set_exit_status(E_ERROR);
#else
struct sigaction sa;
sa.sa_handler = SIG_DFL;
sigfillset(&sa.sa_mask);
sa.sa_flags = 0;
sigaction(sig, &sa, NULL);
raise(sig);
#endif
}
return;
}
#else
// While Windows has some very basic signal handling functions as required
// by C89, they are not really used, and e.g. SIGINT doesn't work exactly
// the way it does on POSIX (Windows creates a new thread for the signal
// handler). Instead, we use SetConsoleCtrlHandler() to catch user
// pressing C-c, because that seems to be the recommended way to do it.
//
// NOTE: This doesn't work under MSYS. Trying with SIGINT doesn't work
// either even if it appeared to work at first. So test using Windows
// console window.
static BOOL WINAPI
signal_handler(DWORD type lzma_attribute((__unused__)))
{
// Since we don't get a signal number which we could raise() at
// signals_exit() like on POSIX, just set the exit status to
// indicate an error, so that we cannot return with zero exit status.
set_exit_status(E_ERROR);
user_abort = true;
return TRUE;
}
extern void
signals_init(void)
{
if (!SetConsoleCtrlHandler(&signal_handler, TRUE))
message_signal_handler();
return;
}
#endif
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