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cpython/Modules/signalmodule.c

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/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.
While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.
STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
******************************************************************/
/* Signal module -- many thanks to Lance Ellinghaus */
#include "Python.h"
#include "intrcheck.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <signal.h>
#ifndef SIG_ERR
#define SIG_ERR ((RETSIGTYPE (*)())-1)
#endif
#ifndef NSIG
#define NSIG (_SIGMAX + 1) /* For QNX */
#endif
/*
NOTES ON THE INTERACTION BETWEEN SIGNALS AND THREADS
When threads are supported, we want the following semantics:
- only the main thread can set a signal handler
- any thread can get a signal handler
- signals are only delivered to the main thread
I.e. we don't support "synchronous signals" like SIGFPE (catching
this doesn't make much sense in Python anyway) nor do we support
signals as a means of inter-thread communication, since not all
thread implementations support that (at least our thread library
doesn't).
We still have the problem that in some implementations signals
generated by the keyboard (e.g. SIGINT) are delivered to all
threads (e.g. SGI), while in others (e.g. Solaris) such signals are
delivered to one random thread (an intermediate possibility would
be to deliver it to the main thread -- POSIX?). For now, we have
a working implementation that works in all three cases -- the
handler ignores signals if getpid() isn't the same as in the main
thread. XXX This is a hack.
*/
#ifdef WITH_THREAD
#include "thread.h"
static long main_thread;
static pid_t main_pid;
#endif
struct PySignal_SignalArrayStruct {
int tripped;
PyObject *func;
};
static struct PySignal_SignalArrayStruct PySignal_SignalHandlerArray[NSIG];
static int PySignal_IsTripped = 0; /* Speed up sigcheck() when none tripped */
static PyObject *PySignal_SignalDefaultHandler;
static PyObject *PySignal_SignalIgnoreHandler;
static PyObject *PySignal_DefaultIntHandler;
static PyObject *
PySignal_CDefaultIntHandler(self, arg)
PyObject *self;
PyObject *arg;
{
PyErr_SetNone(PyExc_KeyboardInterrupt);
return (PyObject *)NULL;
}
void
PyErr_SetInterrupt()
{
PySignal_IsTripped++;
PySignal_SignalHandlerArray[SIGINT].tripped = 1;
}
static RETSIGTYPE
PySignal_Handler(sig_num)
int sig_num;
{
#ifdef WITH_THREAD
/* See NOTES section above */
if (getpid() == main_pid) {
#endif
PySignal_IsTripped++;
PySignal_SignalHandlerArray[sig_num].tripped = 1;
#ifdef WITH_THREAD
}
#endif
#ifdef SIGCHLD
if (sig_num == SIGCHLD) {
/* To avoid infinite recursion, this signal remains
reset until explicit re-instated.
Don't clear the 'func' field as it is our pointer
to the Python handler... */
return;
}
#endif
(void *)signal(sig_num, &PySignal_Handler);
}
#ifndef DONT_HAVE_SIG_ALARM
static PyObject *
PySignal_Alarm(self, args)
PyObject *self; /* Not used */
PyObject *args;
{
int t;
if (!PyArg_Parse(args, "i", &t))
return (PyObject *)NULL;
/* alarm() returns the number of seconds remaining */
return PyInt_FromLong(alarm(t));
}
#endif
#ifndef DONT_HAVE_SIG_PAUSE
static PyObject *
PySignal_Pause(self, args)
PyObject *self; /* Not used */
PyObject *args;
{
if (!PyArg_NoArgs(args))
return NULL;
Py_BEGIN_ALLOW_THREADS
pause();
Py_END_ALLOW_THREADS
Py_INCREF(Py_None);
return Py_None;
}
#endif
static PyObject *
PySignal_Signal(self, args)
PyObject *self; /* Not used */
PyObject *args;
{
PyObject *obj;
int sig_num;
PyObject *old_handler;
RETSIGTYPE (*func)();
if (!PyArg_Parse(args, "(iO)", &sig_num, &obj))
return (PyObject *)NULL;
#ifdef WITH_THREAD
if (get_thread_ident() != main_thread) {
PyErr_SetString(PyExc_ValueError,
"signal only works in main thread");
return (PyObject *)NULL;
}
#endif
if (sig_num < 1 || sig_num >= NSIG) {
PyErr_SetString(PyExc_ValueError,
"signal number out of range");
return (PyObject *)NULL;
}
if (obj == PySignal_SignalIgnoreHandler)
func = SIG_IGN;
else if (obj == PySignal_SignalDefaultHandler)
func = SIG_DFL;
else if (!PyCallable_Check(obj)) {
PyErr_SetString(PyExc_TypeError,
"signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object");
return (PyObject *)NULL;
}
else
func = PySignal_Handler;
if (signal(sig_num, func) == SIG_ERR) {
PyErr_SetFromErrno(PyExc_RuntimeError);
return (PyObject *)NULL;
}
old_handler = PySignal_SignalHandlerArray[sig_num].func;
PySignal_SignalHandlerArray[sig_num].tripped = 0;
Py_INCREF(obj);
PySignal_SignalHandlerArray[sig_num].func = obj;
return old_handler;
}
static PyObject *
PySignal_GetSignal(self, args)
PyObject *self; /* Not used */
PyObject *args;
{
int sig_num;
PyObject *old_handler;
if (!PyArg_Parse(args, "i", &sig_num))
return (PyObject *)NULL;
if (sig_num < 1 || sig_num >= NSIG) {
PyErr_SetString(PyExc_ValueError,
"signal number out of range");
return (PyObject *)NULL;
}
old_handler = PySignal_SignalHandlerArray[sig_num].func;
Py_INCREF(old_handler);
return old_handler;
}
/* List of functions defined in the module */
static PyMethodDef PySignal_methods[] = {
#ifndef DONT_HAVE_SIG_ALARM
{"alarm", PySignal_Alarm},
#endif
{"signal", PySignal_Signal},
{"getsignal", PySignal_GetSignal},
#ifndef DONT_HAVE_SIG_PAUSE
{"pause", PySignal_Pause},
#endif
{"default_int_handler", PySignal_CDefaultIntHandler},
{NULL, NULL} /* sentinel */
};
void
initsignal()
{
PyObject *m, *d, *x;
int i;
#ifdef WITH_THREAD
main_thread = get_thread_ident();
main_pid = getpid();
#endif
/* Create the module and add the functions */
m = Py_InitModule("signal", PySignal_methods);
/* Add some symbolic constants to the module */
d = PyModule_GetDict(m);
PySignal_SignalDefaultHandler = PyInt_FromLong((long)SIG_DFL);
PyDict_SetItemString(d, "SIG_DFL", PySignal_SignalDefaultHandler);
PySignal_SignalIgnoreHandler = PyInt_FromLong((long)SIG_IGN);
PyDict_SetItemString(d, "SIG_IGN", PySignal_SignalIgnoreHandler);
PyDict_SetItemString(d, "NSIG", PyInt_FromLong((long)NSIG));
PySignal_DefaultIntHandler =
PyDict_GetItemString(d, "default_int_handler");
PySignal_SignalHandlerArray[0].tripped = 0;
for (i = 1; i < NSIG; i++) {
RETSIGTYPE (*t)();
#ifdef HAVE_SIGACTION
struct sigaction act;
sigaction(i, 0, &act);
t = act.sa_handler;
#else
t = signal(i, SIG_IGN);
signal(i, t);
#endif
PySignal_SignalHandlerArray[i].tripped = 0;
if (t == SIG_DFL)
PySignal_SignalHandlerArray[i].func =
PySignal_SignalDefaultHandler;
else if (t == SIG_IGN)
PySignal_SignalHandlerArray[i].func =
PySignal_SignalIgnoreHandler;
else
PySignal_SignalHandlerArray[i].func =
Py_None; /* None of our business */
Py_INCREF(PySignal_SignalHandlerArray[i].func);
}
if (PySignal_SignalHandlerArray[SIGINT].func ==
PySignal_SignalDefaultHandler) {
/* Install default int handler */
Py_DECREF(PySignal_SignalHandlerArray[SIGINT].func);
PySignal_SignalHandlerArray[SIGINT].func =
PySignal_DefaultIntHandler;
Py_INCREF(PySignal_DefaultIntHandler);
signal(SIGINT, &PySignal_Handler);
}
#ifdef SIGHUP
x = PyInt_FromLong(SIGHUP);
PyDict_SetItemString(d, "SIGHUP", x);
#endif
#ifdef SIGINT
x = PyInt_FromLong(SIGINT);
PyDict_SetItemString(d, "SIGINT", x);
#endif
#ifdef SIGQUIT
x = PyInt_FromLong(SIGQUIT);
PyDict_SetItemString(d, "SIGQUIT", x);
#endif
#ifdef SIGILL
x = PyInt_FromLong(SIGILL);
PyDict_SetItemString(d, "SIGILL", x);
#endif
#ifdef SIGTRAP
x = PyInt_FromLong(SIGTRAP);
PyDict_SetItemString(d, "SIGTRAP", x);
#endif
#ifdef SIGIOT
x = PyInt_FromLong(SIGIOT);
PyDict_SetItemString(d, "SIGIOT", x);
#endif
#ifdef SIGABRT
x = PyInt_FromLong(SIGABRT);
PyDict_SetItemString(d, "SIGABRT", x);
#endif
#ifdef SIGEMT
x = PyInt_FromLong(SIGEMT);
PyDict_SetItemString(d, "SIGEMT", x);
#endif
#ifdef SIGFPE
x = PyInt_FromLong(SIGFPE);
PyDict_SetItemString(d, "SIGFPE", x);
#endif
#ifdef SIGKILL
x = PyInt_FromLong(SIGKILL);
PyDict_SetItemString(d, "SIGKILL", x);
#endif
#ifdef SIGBUS
x = PyInt_FromLong(SIGBUS);
PyDict_SetItemString(d, "SIGBUS", x);
#endif
#ifdef SIGSEGV
x = PyInt_FromLong(SIGSEGV);
PyDict_SetItemString(d, "SIGSEGV", x);
#endif
#ifdef SIGSYS
x = PyInt_FromLong(SIGSYS);
PyDict_SetItemString(d, "SIGSYS", x);
#endif
#ifdef SIGPIPE
x = PyInt_FromLong(SIGPIPE);
PyDict_SetItemString(d, "SIGPIPE", x);
#endif
#ifdef SIGALRM
x = PyInt_FromLong(SIGALRM);
PyDict_SetItemString(d, "SIGALRM", x);
#endif
#ifdef SIGTERM
x = PyInt_FromLong(SIGTERM);
PyDict_SetItemString(d, "SIGTERM", x);
#endif
#ifdef SIGUSR1
x = PyInt_FromLong(SIGUSR1);
PyDict_SetItemString(d, "SIGUSR1", x);
#endif
#ifdef SIGUSR2
x = PyInt_FromLong(SIGUSR2);
PyDict_SetItemString(d, "SIGUSR2", x);
#endif
#ifdef SIGCLD
x = PyInt_FromLong(SIGCLD);
PyDict_SetItemString(d, "SIGCLD", x);
#endif
#ifdef SIGCHLD
x = PyInt_FromLong(SIGCHLD);
PyDict_SetItemString(d, "SIGCHLD", x);
#endif
#ifdef SIGPWR
x = PyInt_FromLong(SIGPWR);
PyDict_SetItemString(d, "SIGPWR", x);
#endif
#ifdef SIGIO
x = PyInt_FromLong(SIGIO);
PyDict_SetItemString(d, "SIGIO", x);
#endif
#ifdef SIGURG
x = PyInt_FromLong(SIGURG);
PyDict_SetItemString(d, "SIGURG", x);
#endif
#ifdef SIGWINCH
x = PyInt_FromLong(SIGWINCH);
PyDict_SetItemString(d, "SIGWINCH", x);
#endif
#ifdef SIGPOLL
x = PyInt_FromLong(SIGPOLL);
PyDict_SetItemString(d, "SIGPOLL", x);
#endif
#ifdef SIGSTOP
x = PyInt_FromLong(SIGSTOP);
PyDict_SetItemString(d, "SIGSTOP", x);
#endif
#ifdef SIGTSTP
x = PyInt_FromLong(SIGTSTP);
PyDict_SetItemString(d, "SIGTSTP", x);
#endif
#ifdef SIGCONT
x = PyInt_FromLong(SIGCONT);
PyDict_SetItemString(d, "SIGCONT", x);
#endif
#ifdef SIGTTIN
x = PyInt_FromLong(SIGTTIN);
PyDict_SetItemString(d, "SIGTTIN", x);
#endif
#ifdef SIGTTOU
x = PyInt_FromLong(SIGTTOU);
PyDict_SetItemString(d, "SIGTTOU", x);
#endif
#ifdef SIGVTALRM
x = PyInt_FromLong(SIGVTALRM);
PyDict_SetItemString(d, "SIGVTALRM", x);
#endif
#ifdef SIGPROF
x = PyInt_FromLong(SIGPROF);
PyDict_SetItemString(d, "SIGPROF", x);
#endif
#ifdef SIGCPU
x = PyInt_FromLong(SIGCPU);
PyDict_SetItemString(d, "SIGCPU", x);
#endif
#ifdef SIGXCPU
x = PyInt_FromLong(SIGXCPU);
PyDict_SetItemString(d, "SIGXCPU", x);
#endif
#ifdef SIGFSZ
x = PyInt_FromLong(SIGFSZ);
PyDict_SetItemString(d, "SIGFSZ", x);
#endif
#ifdef SIGXFSZ
x = PyInt_FromLong(SIGXFSZ);
PyDict_SetItemString(d, "SIGXFSZ", x);
#endif
/* Check for errors */
if (PyErr_Occurred())
Py_FatalError("can't initialize module signal");
}
int
PyErr_CheckSignals()
{
int i;
PyObject *f;
if (!PySignal_IsTripped)
return 0;
#ifdef WITH_THREAD
if (get_thread_ident() != main_thread)
return 0;
#endif
f = PyEval_GetFrame();
if (f == (PyObject *)NULL)
f = Py_None;
for (i = 1; i < NSIG; i++) {
if (PySignal_SignalHandlerArray[i].tripped) {
PyObject *arglist, *result;
PySignal_SignalHandlerArray[i].tripped = 0;
arglist = Py_BuildValue("(iO)", i, f);
if (arglist == (PyObject *)NULL)
result = (PyObject *)NULL;
else {
result = PyEval_CallObject(
PySignal_SignalHandlerArray[i].func, arglist);
Py_DECREF(arglist);
}
if (result == (PyObject *)NULL) {
return 1;
} else {
Py_DECREF(result);
}
}
}
PySignal_IsTripped = 0;
return 0;
}
/* Replacement for intrcheck.c functionality */
void
PyOS_InitInterrupts ()
{
initsignal();
}
int
PyOS_InterruptOccurred ()
{
if (PySignal_SignalHandlerArray[SIGINT].tripped) {
#ifdef WITH_THREAD
if (get_thread_ident() != main_thread)
return 0;
#endif
PySignal_SignalHandlerArray[SIGINT].tripped = 0;
return 1;
}
return 0;
}
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