mercury/compiler/process_util.m

%-----------------------------------------------------------------------------%
% Copyright (C) 2002-2003 University of Melbourne.
% This file may only be copied under the terms of the GNU General
% Public License - see the file COPYING in the Mercury distribution.
%-----------------------------------------------------------------------------%
% File: process_util.m
% Main author: stayl
%
% Process and signal handling, mainly for use by make.m and its sub-modules.
%-----------------------------------------------------------------------------%
:- module libs__process_util.

:- interface.

:- import_module bool, io.

%-----------------------------------------------------------------------------%

:- type build0(Info) == pred(bool, Info, Info, io__state, io__state).
:- inst build0 == (pred(out, in, out, di, uo) is det).

:- type post_signal_cleanup(Info) == pred(Info, Info, io__state, io__state).
:- inst post_signal_cleanup == (pred(in, out, di, uo) is det).

	% build_with_check_for_interrupt(Build, Cleanup,
	%	Succeeded, Info0, Info)
	%
	% Apply `Build' with signal handlers installed to check for signals
	% which would normally kill the process. If a signal occurs call
	% `Cleanup', then restore signal handlers to their defaults and
	% reraise the signal to kill the current process.
	% An action being performed in a child process by
	% call_in_forked_process will be killed if a fatal signal
	% (SIGINT, SIGTERM, SIGHUP or SIGQUIT) is received by the
	% current process.
	% An action being performed within the current process or by
	% system() will run to completion, with the interrupt being taken
	% immediately afterwards.
:- pred build_with_check_for_interrupt(build0(Info)::in(build0),
	post_signal_cleanup(Info)::in(post_signal_cleanup), bool::out,
	Info::in, Info::out, io__state::di, io__state::uo) is det.

	% raise_signal(Signal).
	% Send `Signal' to the current process.
:- pred raise_signal(int::in, io__state::di, io__state::uo) is det.

%-----------------------------------------------------------------------------%

:- type io_pred == pred(bool, io__state, io__state).
:- inst io_pred == (pred(out, di, uo) is det).

	% call_in_forked_process(P, AltP, Succeeded)
	%
	% Execute `P' in a separate process.
	%
	% We prefer to use fork() rather than system() because
	% that will avoid shell and Mercury runtime startup overhead.
	% Interrupt handling will also work better (system() on Linux
	% ignores SIGINT).
	%
	% If fork() is not supported on the current architecture,
	% `AltP' will be called instead in the current process.
:- pred call_in_forked_process(io_pred::in(io_pred), io_pred::in(io_pred),
	bool::out, io__state::di, io__state::uo) is det.

	% As above, but if fork() is not available, just call the
	% predicate in the current process.
:- pred call_in_forked_process(io_pred::in(io_pred),
	bool::out, io__state::di, io__state::uo) is det.

%-----------------------------------------------------------------------------%

:- implementation.

:- import_module libs__globals.
:- import_module libs__options.

:- import_module std_util, require.

build_with_check_for_interrupt(Build, Cleanup, Succeeded, Info0, Info) -->
	setup_signal_handlers(MaybeSigIntHandler),
	Build(Succeeded0, Info0, Info1),
	restore_signal_handlers(MaybeSigIntHandler),
	check_for_signal(Signalled, Signal),
	( { Signalled = 1 } ->
		{ Succeeded = no },
		globals__io_lookup_bool_option(verbose_make, Verbose),
		( { Verbose = yes } ->
			io__write_string("** Received signal "),
			io__write_int(Signal),
			io__write_string(", cleaning up.\n")
		;
			[]
		),
		Cleanup(Info1, Info),

		% The signal handler has been restored to the default,
		% so this should kill us.
		raise_signal(Signal)
	;
		{ Succeeded = Succeeded0 },
		{ Info = Info1 }
	).	

:- type signal_action ---> signal_action.
:- pragma foreign_type("C", signal_action, "MR_signal_action").

:- pragma foreign_decl("C",
"
#ifdef MR_HAVE_UNISTD_H
  #include <unistd.h>
#endif

#ifdef MR_HAVE_SYS_TYPES_H
  #include <sys/types.h>
#endif

#ifdef MR_HAVE_SYS_WAIT_H
  #include <sys/wait.h>
#endif

#include <errno.h>

#include ""mercury_signal.h""
#include ""mercury_types.h""
#include ""mercury_heap.h""
#include ""mercury_misc.h""

#if defined(MR_HAVE_FORK) && defined(MR_HAVE_WAIT) && defined(MR_HAVE_KILL)
  #define MC_CAN_FORK 1
#endif

#define MC_SETUP_SIGNAL_HANDLER(sig, handler) \
		MR_setup_signal(sig, (MR_Code *) handler, MR_FALSE,	\
			""mercury_compile: cannot install signal handler"");

	/* Have we received a signal. */
extern volatile sig_atomic_t MC_signalled;

	/*
	** Which signal did we receive.
	** XXX This assumes a signal number will fit into a sig_atomic_t.
	*/
extern volatile sig_atomic_t MC_signal_received;

void MC_mercury_compile_signal_handler(int sig);
").

:- pragma foreign_code("C",
"
volatile sig_atomic_t MC_signalled = MR_FALSE;
volatile sig_atomic_t MC_signal_received = 0;

void
MC_mercury_compile_signal_handler(int sig)
{
	MC_signalled = MR_TRUE;
	MC_signal_received = sig;
}
").

:- pred setup_signal_handlers(signal_action::out,
		io__state::di, io__state::uo) is det.

setup_signal_handlers(signal_action::out, IO::di, IO::uo).

:- pragma foreign_proc("C",
	setup_signal_handlers(SigintHandler::out, IO0::di, IO::uo),
	[will_not_call_mercury, promise_pure, tabled_for_io],
"{
	IO = IO0;
	MC_signalled = MR_FALSE;

	/*
	** mdb sets up a SIGINT handler, so we should restore
	** it after we're done.
	*/
	MR_get_signal_action(SIGINT, &SigintHandler,
		""error getting SIGINT handler"");
	MC_SETUP_SIGNAL_HANDLER(SIGINT, MC_mercury_compile_signal_handler);
	MC_SETUP_SIGNAL_HANDLER(SIGTERM, MC_mercury_compile_signal_handler);
#ifdef SIGHUP
	MC_SETUP_SIGNAL_HANDLER(SIGHUP, MC_mercury_compile_signal_handler);
#endif
#ifdef SIGQUIT
	MC_SETUP_SIGNAL_HANDLER(SIGQUIT, MC_mercury_compile_signal_handler);
#endif
}").

:- pred restore_signal_handlers(signal_action::in,
		io__state::di, io__state::uo) is det.

restore_signal_handlers(_::in, IO::di, IO::uo).

:- pragma foreign_proc("C",
	restore_signal_handlers(SigintHandler::in, IO0::di, IO::uo),
	[will_not_call_mercury, promise_pure, tabled_for_io],
"{
	IO = IO0;
	MR_set_signal_action(SIGINT, &SigintHandler,
		""error resetting SIGINT handler"");
	MC_SETUP_SIGNAL_HANDLER(SIGTERM, SIG_DFL);
#ifdef SIGHUP
	MC_SETUP_SIGNAL_HANDLER(SIGHUP, SIG_DFL);
#endif
#ifdef SIGQUIT
	MC_SETUP_SIGNAL_HANDLER(SIGQUIT, SIG_DFL);
#endif
}").

	% Restore all signal handlers to default values in the child
	% so that the child will be killed by the signals the parent
	% is catching.
:- pred setup_child_signal_handlers(io__state::di, io__state::uo) is det.

setup_child_signal_handlers -->
	restore_signal_handlers(sig_dfl).

:- func sig_dfl = signal_action.

sig_dfl = (signal_action::out).

:- pragma foreign_proc("C", sig_dfl = (Result::out),
		[will_not_call_mercury, promise_pure],
	"MR_init_signal_action(&Result, SIG_DFL, MR_FALSE, MR_TRUE);").

:- pred check_for_signal(int::out, int::out,
		io__state::di, io__state::uo) is det.

check_for_signal(0::out, 0::out, IO::di, IO::uo).

:- pragma foreign_proc("C",
	check_for_signal(Signalled::out, Signal::out, IO0::di, IO::uo),
	[will_not_call_mercury, promise_pure, tabled_for_io],
"
	IO = IO0;
	Signalled = (MC_signalled ? 1 : 0);
	Signal = MC_signal_received;
").

%-----------------------------------------------------------------------------%

:- pragma foreign_decl("C", "#include <signal.h>").

	% If this aborted it would cause partially built files
	% to be left lying around with `--make'.
raise_signal(_::in, IO::di, IO::uo).

:- pragma foreign_proc("C",
	raise_signal(Signal::in, IO0::di, IO::uo),
	[will_not_call_mercury, promise_pure, tabled_for_io],
"
	IO = IO0;
	raise(Signal);
").

%-----------------------------------------------------------------------------%

call_in_forked_process(P, Success) -->
	call_in_forked_process(P, P, Success).

call_in_forked_process(P, AltP, Success) -->
	( { can_fork(1) } ->
		call_in_forked_process_2(P, ForkStatus, CallStatus),
		{ ForkStatus = 1 ->
			Success = no
		;
			Status = io__handle_system_command_exit_status(
					CallStatus),
			Success = (Status = ok(exited(0)) -> yes ; no)
		}
	;
		AltP(Success)
	).

	% Dummy argument to work around bug mixing Mercury and foreign clauses.
:- pred can_fork(T::unused) is semidet.

can_fork(_::unused) :- semidet_fail.

:- pragma foreign_proc("C", can_fork(_T::unused),
		[will_not_call_mercury, thread_safe, promise_pure],
"
#ifdef MC_CAN_FORK
	SUCCESS_INDICATOR = MR_TRUE;
#else
	SUCCESS_INDICATOR = MR_FALSE;
#endif
").

:- pred call_in_forked_process_2(io_pred::in(io_pred), int::out, int::out,
		io__state::di, io__state::uo) is det.

call_in_forked_process_2(_::in(io_pred), _::out, _::out, _::di, _::uo) :-
	error("call_in_forked_process_2").

:- pragma foreign_proc("C",
	call_in_forked_process_2(Pred::in(io_pred),
		ForkStatus::out, Status::out, IO0::di, IO::uo),
	[may_call_mercury, promise_pure, tabled_for_io],
"{
#ifdef MC_CAN_FORK
	pid_t child_pid;

	IO = IO0;
	ForkStatus = 0;
	Status = 0;

	child_pid = fork();
	if (child_pid == -1) {		/* error */
		MR_perror(""error in fork()"");
		ForkStatus = 1;
	} else if (child_pid == 0) {	/* child */
		MR_Integer exit_status;

		MC_call_child_process_io_pred(Pred, &exit_status);
		exit(exit_status);
	} else {			/* parent */
		int child_status;
		pid_t wait_status;

		/*
		** Make sure the wait() is interrupted by the signals
		** which cause us to exit.
		*/
		MR_signal_should_restart(SIGINT, MR_FALSE);
		MR_signal_should_restart(SIGTERM, MR_FALSE);
#ifdef SIGHUP
		MR_signal_should_restart(SIGHUP, MR_FALSE);
#endif
#ifdef SIGQUIT
		MR_signal_should_restart(SIGQUIT, MR_FALSE);
#endif

		while (1) {
		    wait_status = wait(&child_status);
		    if (wait_status == child_pid) {
			Status = child_status;
			break;
		    } else if (wait_status == -1) {
			if (MR_is_eintr(errno)) {
			    if (MC_signalled) {
				/*
				** A normally fatal signal has been received,
				** so kill the child immediately.
				** Use SIGTERM, not MC_signal_received,
				** because the child may be inside a call
				** to system() which would cause SIGINT
				** to be ignored on some systems (e.g. Linux).
				*/
				kill(child_pid, SIGTERM);
				break;
			    }
			} else {
			    /*
			    ** This should never happen.
			    */
			    MR_perror(""error in wait(): "");
			    ForkStatus = 1;
			    Status = 1;
			    break;
			}
		    }
		}

		/*
		** Restore the system call signal behaviour. 
		*/
		MR_signal_should_restart(SIGINT, MR_TRUE);
		MR_signal_should_restart(SIGTERM, MR_TRUE);
#ifdef SIGHUP
		MR_signal_should_restart(SIGHUP, MR_TRUE);
#endif
#ifdef SIGQUIT
		MR_signal_should_restart(SIGQUIT, MR_TRUE);
#endif

	}
#else /* ! MC_CAN_FORK */
	IO = IO0;
	ForkStatus = 1;
	Status = 1;
#endif /* ! MC_CAN_FORK */
}").

	% call_child_process_io_pred(P, ExitStatus).
:- pred call_child_process_io_pred(io_pred::in(io_pred), int::out,
		io__state::di, io__state::uo) is det.
:- pragma export(call_child_process_io_pred(in(io_pred), out, di, uo),
		"MC_call_child_process_io_pred").

call_child_process_io_pred(P, Status) -->
	setup_child_signal_handlers,
	P(Success),
	{ Status = ( Success = yes -> 0 ; 1 ) }.

%-----------------------------------------------------------------------------%