A lua-signal updated for lua 5.2, compile with "gcc -fPIC -shared signal.c -o signal.o". See https://github.com/LuaDist/lua-signal for API notes and the 5.1 version.

signal.c

/*
 * signal.c -- Signal Handler Library for Lua
 *
 * Version: 1.000+changes
 *
 * Copyright (C) 2007  Patrick J. Donnelly (batrick@batbytes.com)
 *
 * This software is distributed under the same license as Lua 5.0:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE. 
*/

#include <signal.h>
#include <stdlib.h>

#include "lua.h"
#include "lauxlib.h"

#ifndef lsig

#define lsig

struct lua_signal
{
  char *name; /* name of the signal */
  int sig; /* the signal */
};

#endif

#define LUA_SIGNAL "lua_signal"

static const struct lua_signal lua_signals[] = {
  /* ANSI C signals */
#ifdef SIGABRT
  {"SIGABRT", SIGABRT},
#endif
#ifdef SIGFPE
  {"SIGFPE", SIGFPE},
#endif
#ifdef SIGILL
  {"SIGILL", SIGILL},
#endif
#ifdef SIGINT
  {"SIGINT", SIGINT},
#endif
#ifdef SIGSEGV
  {"SIGSEGV", SIGSEGV},
#endif
#ifdef SIGTERM
  {"SIGTERM", SIGTERM},
#endif
  /* posix signals */
#ifdef SIGHUP
  {"SIGHUP", SIGHUP},
#endif
#ifdef SIGQUIT
  {"SIGQUIT", SIGQUIT},
#endif
#ifdef SIGTRAP
  {"SIGTRAP", SIGTRAP},
#endif
#ifdef SIGKILL
  {"SIGKILL", SIGKILL},
#endif
#ifdef SIGUSR1
  {"SIGUSR1", SIGUSR1},
#endif
#ifdef SIGUSR2
  {"SIGUSR2", SIGUSR2},
#endif
#ifdef SIGPIPE
  {"SIGPIPE", SIGPIPE},
#endif
#ifdef SIGALRM
  {"SIGALRM", SIGALRM},
#endif
#ifdef SIGCHLD
  {"SIGCHLD", SIGCHLD},
#endif
#ifdef SIGCONT
  {"SIGCONT", SIGCONT},
#endif
#ifdef SIGSTOP
  {"SIGSTOP", SIGSTOP},
#endif
#ifdef SIGTTIN
  {"SIGTTIN", SIGTTIN},
#endif
#ifdef SIGTTOU
  {"SIGTTOU", SIGTTOU},
#endif
  /* some BSD signals */
#ifdef SIGIOT
  {"SIGIOT", SIGIOT},
#endif
#ifdef SIGBUS
  {"SIGBUS", SIGBUS},
#endif
#ifdef SIGCLD
  {"SIGCLD", SIGCLD},
#endif
#ifdef SIGURG
  {"SIGURG", SIGURG},
#endif
#ifdef SIGXCPU
  {"SIGXCPU", SIGXCPU},
#endif
#ifdef SIGXFSZ
  {"SIGXFSZ", SIGXFSZ},
#endif
#ifdef SIGVTALRM
  {"SIGVTALRM", SIGVTALRM},
#endif
#ifdef SIGPROF
  {"SIGPROF", SIGPROF},
#endif
#ifdef SIGWINCH
  {"SIGWINCH", SIGWINCH},
#endif
#ifdef SIGPOLL
  {"SIGPOLL", SIGPOLL},
#endif
#ifdef SIGIO
  {"SIGIO", SIGIO},
#endif
  /* add odd signals */
#ifdef SIGSTKFLT
  {"SIGSTKFLT", SIGSTKFLT}, /* stack fault */
#endif
#ifdef SIGSYS
  {"SIGSYS", SIGSYS},
#endif
  {NULL, 0}
};

static lua_State *Lsig = NULL;
static lua_Hook Hsig = NULL;
static int Hmask = 0;
static int Hcount = 0;

static struct signal_event
{
	int Nsig;
	struct signal_event *next_event;
} *signal_queue = NULL;

static struct signal_event *last_event = NULL;

static void sighook(lua_State *L, lua_Debug *ar)
{
  struct signal_event *event;
  /* restore the old hook */
  lua_sethook(L, Hsig, Hmask, Hcount);

  lua_pushstring(L, LUA_SIGNAL);
  lua_gettable(L, LUA_REGISTRYINDEX);

  while((event = signal_queue))
  {
    lua_pushnumber(L, event->Nsig);
    lua_gettable(L, -2);
    lua_call(L, 0, 0);
    signal_queue = event->next_event;
    free(event);
  };

  lua_pop(L, 1); /* pop lua_signal table */

}

static void handle(int sig)
{
  if(!signal_queue)
  {
    /* Store the existing debug hook (if any) and its parameters */
    Hsig = lua_gethook(Lsig);
    Hmask = lua_gethookmask(Lsig);
    Hcount = lua_gethookcount(Lsig);
    
    signal_queue = malloc(sizeof(struct signal_event));
    signal_queue->Nsig = sig;
    signal_queue->next_event = NULL;

    last_event = signal_queue;
    
    /* Set our new debug hook */
    lua_sethook(Lsig, sighook, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT, 1);
  }
  else
  {
    last_event->next_event = malloc(sizeof(struct signal_event));
    last_event->next_event->Nsig = sig;
    last_event->next_event->next_event = NULL;
    
    last_event = last_event->next_event;
  }
}

/*
 * l_signal == signal(signal [, func [, chook]])
 *
 * signal = signal number or string
 * func = Lua function to call
 * chook = catch within C functions
 *         if caught, Lua function _must_
 *         exit, as the stack is most likely
 *         in an unstable state.
*/  

static int l_signal(lua_State *L)
{
  int args = lua_gettop(L);
  int t, sig; /* type, signal */

  /* get type of signal */
  luaL_checkany(L, 1);
  t = lua_type(L, 1);
  if (t == LUA_TNUMBER)
    sig = (int) lua_tonumber(L, 1);
  else if (t == LUA_TSTRING)
  {
    lua_pushstring(L, LUA_SIGNAL);
    lua_gettable(L, LUA_REGISTRYINDEX);
    lua_pushvalue(L, 1);
    lua_gettable(L, -2);
    if (!lua_isnumber(L, -1))
      luaL_error(L, "invalid signal string");
    sig = (int) lua_tonumber(L, -1);
    lua_pop(L, 1); /* get rid of number we pushed */
  } else
    luaL_checknumber(L, 1); /* will always error, with good error msg */

  /* set handler */
  if (args == 1 || lua_isnil(L, 2)) /* clear handler */
  {
    lua_pushstring(L, LUA_SIGNAL);
    lua_gettable(L, LUA_REGISTRYINDEX);
    lua_pushnumber(L, sig);
    lua_gettable(L, -2); /* return old handler */
    lua_pushnumber(L, sig);
    lua_pushnil(L);
    lua_settable(L, -4);
    lua_remove(L, -2); /* remove LUA_SIGNAL table */
    signal(sig, SIG_DFL);
  } else
  {
    luaL_checktype(L, 2, LUA_TFUNCTION);

    lua_pushstring(L, LUA_SIGNAL);
    lua_gettable(L, LUA_REGISTRYINDEX);

    lua_pushnumber(L, sig);
    lua_pushvalue(L, 2);
    lua_settable(L, -3);

    /* Set the state for the handler */
    Lsig = L;

    if (lua_toboolean(L, 3)) /* c hook? */
    {
      if (signal(sig, handle) == SIG_ERR)
        lua_pushboolean(L, 0);
      else
        lua_pushboolean(L, 1);
    } else /* lua_hook */
    {
      if (signal(sig, handle) == SIG_ERR)
        lua_pushboolean(L, 0);
      else
        lua_pushboolean(L, 1);
    }
  }
  return 1;
}

/*
 * l_raise == raise(signal)
 *
 * signal = signal number or string
*/  

static int l_raise(lua_State *L)
{
  /* int args = lua_gettop(L); */
  int t = 0; /* type */
  lua_Number ret;

  luaL_checkany(L, 1);

  t = lua_type(L, 1);
  if (t == LUA_TNUMBER)
  {
    ret = (lua_Number) raise((int) lua_tonumber(L, 1));
    lua_pushnumber(L, ret);
  } else if (t == LUA_TSTRING)
  {
    lua_pushstring(L, LUA_SIGNAL);
    lua_gettable(L, LUA_REGISTRYINDEX);
    lua_pushvalue(L, 1);
    lua_gettable(L, -2);
    if (!lua_isnumber(L, -1))
      luaL_error(L, "invalid signal string");
    ret = (lua_Number) raise((int) lua_tonumber(L, -1));
    lua_pop(L, 1); /* get rid of number we pushed */
    lua_pushnumber(L, ret);
  } else
    luaL_checknumber(L, 1); /* will always error, with good error msg */

  return 1;
}

#if defined(__unix__) || defined(__APPLE__)

/* define some posix only functions */

/*
 * l_kill == kill(pid, signal)
 *
 * pid = process id
 * signal = signal number or string
*/  

static int l_kill(lua_State *L)
{
  int t; /* type */
  lua_Number ret; /* return value */

  luaL_checknumber(L, 1); /* must be int for pid */
  luaL_checkany(L, 2); /* check for a second arg */

  t = lua_type(L, 2);
  if (t == LUA_TNUMBER)
  {
    ret = (lua_Number) kill((int) lua_tonumber(L, 1),
        (int) lua_tonumber(L, 2));
    lua_pushnumber(L, ret);
  } else if (t == LUA_TSTRING)
  {
    lua_pushstring(L, LUA_SIGNAL);
    lua_gettable(L, LUA_REGISTRYINDEX);
    lua_pushvalue(L, 2);
    lua_gettable(L, -2);
    if (!lua_isnumber(L, -1))
      luaL_error(L, "invalid signal string");
    ret = (lua_Number) kill((int) lua_tonumber(L, 1),
        (int) lua_tonumber(L, -1));
    lua_pop(L, 1); /* get rid of number we pushed */
    lua_pushnumber(L, ret);
  } else
    luaL_checknumber(L, 2); /* will always error, with good error msg */
  return 1;
}

#endif

static const struct luaL_Reg lsignal_lib[] = {
  {"signal", l_signal},
  {"raise", l_raise},
#if defined(__unix__) || defined(__APPLE__)
  {"kill", l_kill},
#endif
  {NULL, NULL}
};

int luaopen_signal(lua_State *L)
{
  int i = 0;

  /* add the library */
  lua_newtable(L);
  luaL_setfuncs(L, lsignal_lib, 0);

  /* push lua_signals table into the registry */
  /* put the signals inside the library table too,
   * they are only a reference */
  lua_pushstring(L, LUA_SIGNAL);
  lua_createtable(L, 0, 0);

  while (lua_signals[i].name != NULL)
  {
    /* registry table */
    lua_pushstring(L, lua_signals[i].name);
    lua_pushnumber(L, lua_signals[i].sig);
    lua_settable(L, -3);
    /* signal table */
    lua_pushstring(L, lua_signals[i].name);
    lua_pushnumber(L, lua_signals[i].sig);
    lua_settable(L, -5);
    i++;
  }

  /* add newtable to the registry */
  lua_settable(L, LUA_REGISTRYINDEX);

  return 1;
}