strsignal.c

/* Extended support for using signal values.
   Written by Fred Fish.  fnf@cygnus.com
   This file is in the public domain.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

/* We need to declare sys_siglist, because even if the system provides
   it we can't assume that it is declared in <signal.h> (for example,
   SunOS provides sys_siglist, but it does not declare it in any
   header file).  fHowever, we can't declare sys_siglist portably,
   because on some systems it is declared with const and on some
   systems it is declared without const.  If we were using autoconf,
   we could work out the right declaration.  Until, then we just
   ignore any declaration in the system header files, and always
   declare it ourselves.  With luck, this will always work.  */
#define sys_siglist no_such_symbol
#define sys_nsig sys_nsig__no_such_symbol

#include <stdio.h>
#include <signal.h>

/*  Routines imported from standard C runtime libraries. */

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#else
extern PTR malloc ();
#endif

#ifdef HAVE_STRING_H
#include <string.h>
#else
extern PTR memset ();
#endif

/* Undefine the macro we used to hide the definition of sys_siglist
   found in the system header files.  */
#undef sys_siglist
#undef sys_nsig

#ifndef NULL
#  ifdef __STDC__
#    define NULL (void *) 0
#  else
#    define NULL 0
#  endif
#endif

#ifndef MAX
#  define MAX(a,b) ((a) > (b) ? (a) : (b))
#endif

static void init_signal_tables(void);

/* Translation table for signal values.

   Note that this table is generally only accessed when it is used at runtime
   to initialize signal name and message tables that are indexed by signal
   value.

   Not all of these signals will exist on all systems.  This table is the only
   thing that should have to be updated as new signal numbers are introduced.
   It's sort of ugly, but at least its portable. */

struct signal_info
{
  const int value;		/* The numeric value from <signal.h> */
  const char *const name;	/* The equivalent symbolic value */
#ifndef HAVE_SYS_SIGLIST
  const char *const msg;	/* Short message about this value */
#endif
};

#ifndef HAVE_SYS_SIGLIST
#   define ENTRY(value, name, msg)	{value, name, msg}
#else
#   define ENTRY(value, name, msg)	{value, name}
#endif

static const struct signal_info signal_table[] =
{
#if defined (SIGHUP)
  ENTRY(SIGHUP, "SIGHUP", "Hangup"),
#endif
#if defined (SIGINT)
  ENTRY(SIGINT, "SIGINT", "Interrupt"),
#endif
#if defined (SIGQUIT)
  ENTRY(SIGQUIT, "SIGQUIT", "Quit"),
#endif
#if defined (SIGILL)
  ENTRY(SIGILL, "SIGILL", "Illegal instruction"),
#endif
#if defined (SIGTRAP)
  ENTRY(SIGTRAP, "SIGTRAP", "Trace/breakpoint trap"),
#endif
/* Put SIGIOT before SIGABRT, so that if SIGIOT==SIGABRT then SIGABRT
   overrides SIGIOT.  SIGABRT is in ANSI and POSIX.1, and SIGIOT isn't. */
#if defined (SIGIOT)
  ENTRY(SIGIOT, "SIGIOT", "IOT trap"),
#endif
#if defined (SIGABRT)
  ENTRY(SIGABRT, "SIGABRT", "Aborted"),
#endif
#if defined (SIGEMT)
  ENTRY(SIGEMT, "SIGEMT", "Emulation trap"),
#endif
#if defined (SIGFPE)
  ENTRY(SIGFPE, "SIGFPE", "Arithmetic exception"),
#endif
#if defined (SIGKILL)
  ENTRY(SIGKILL, "SIGKILL", "Killed"),
#endif
#if defined (SIGBUS)
  ENTRY(SIGBUS, "SIGBUS", "Bus error"),
#endif
#if defined (SIGSEGV)
  ENTRY(SIGSEGV, "SIGSEGV", "Segmentation fault"),
#endif
#if defined (SIGSYS)
  ENTRY(SIGSYS, "SIGSYS", "Bad system call"),
#endif
#if defined (SIGPIPE)
  ENTRY(SIGPIPE, "SIGPIPE", "Broken pipe"),
#endif
#if defined (SIGALRM)
  ENTRY(SIGALRM, "SIGALRM", "Alarm clock"),
#endif
#if defined (SIGTERM)
  ENTRY(SIGTERM, "SIGTERM", "Terminated"),
#endif
#if defined (SIGUSR1)
  ENTRY(SIGUSR1, "SIGUSR1", "User defined signal 1"),
#endif
#if defined (SIGUSR2)
  ENTRY(SIGUSR2, "SIGUSR2", "User defined signal 2"),
#endif
/* Put SIGCLD before SIGCHLD, so that if SIGCLD==SIGCHLD then SIGCHLD
   overrides SIGCLD.  SIGCHLD is in POXIX.1 */
#if defined (SIGCLD)
  ENTRY(SIGCLD, "SIGCLD", "Child status changed"),
#endif
#if defined (SIGCHLD)
  ENTRY(SIGCHLD, "SIGCHLD", "Child status changed"),
#endif
#if defined (SIGPWR)
  ENTRY(SIGPWR, "SIGPWR", "Power fail/restart"),
#endif
#if defined (SIGWINCH)
  ENTRY(SIGWINCH, "SIGWINCH", "Window size changed"),
#endif
#if defined (SIGURG)
  ENTRY(SIGURG, "SIGURG", "Urgent I/O condition"),
#endif
#if defined (SIGIO)
  /* "I/O pending" has also been suggested, but is misleading since the
     signal only happens when the process has asked for it, not everytime
     I/O is pending. */
  ENTRY(SIGIO, "SIGIO", "I/O possible"),
#endif
#if defined (SIGPOLL)
  ENTRY(SIGPOLL, "SIGPOLL", "Pollable event occurred"),
#endif
#if defined (SIGSTOP)
  ENTRY(SIGSTOP, "SIGSTOP", "Stopped (signal)"),
#endif
#if defined (SIGTSTP)
  ENTRY(SIGTSTP, "SIGTSTP", "Stopped (user)"),
#endif
#if defined (SIGCONT)
  ENTRY(SIGCONT, "SIGCONT", "Continued"),
#endif
#if defined (SIGTTIN)
  ENTRY(SIGTTIN, "SIGTTIN", "Stopped (tty input)"),
#endif
#if defined (SIGTTOU)
  ENTRY(SIGTTOU, "SIGTTOU", "Stopped (tty output)"),
#endif
#if defined (SIGVTALRM)
  ENTRY(SIGVTALRM, "SIGVTALRM", "Virtual timer expired"),
#endif
#if defined (SIGPROF)
  ENTRY(SIGPROF, "SIGPROF", "Profiling timer expired"),
#endif
#if defined (SIGXCPU)
  ENTRY(SIGXCPU, "SIGXCPU", "CPU time limit exceeded"),
#endif
#if defined (SIGXFSZ)
  ENTRY(SIGXFSZ, "SIGXFSZ", "File size limit exceeded"),
#endif
#if defined (SIGWIND)
  ENTRY(SIGWIND, "SIGWIND", "SIGWIND"),
#endif
#if defined (SIGPHONE)
  ENTRY(SIGPHONE, "SIGPHONE", "SIGPHONE"),
#endif
#if defined (SIGLOST)
  ENTRY(SIGLOST, "SIGLOST", "Resource lost"),
#endif
#if defined (SIGWAITING)
  ENTRY(SIGWAITING, "SIGWAITING", "Process's LWPs are blocked"),
#endif
#if defined (SIGLWP)
  ENTRY(SIGLWP, "SIGLWP", "Signal LWP"),
#endif
#if defined (SIGDANGER)
  ENTRY(SIGDANGER, "SIGDANGER", "Swap space dangerously low"),
#endif
#if defined (SIGGRANT)
  ENTRY(SIGGRANT, "SIGGRANT", "Monitor mode granted"),
#endif
#if defined (SIGRETRACT)
  ENTRY(SIGRETRACT, "SIGRETRACT", "Need to relinguish monitor mode"),
#endif
#if defined (SIGMSG)
  ENTRY(SIGMSG, "SIGMSG", "Monitor mode data available"),
#endif
#if defined (SIGSOUND)
  ENTRY(SIGSOUND, "SIGSOUND", "Sound completed"),
#endif
#if defined (SIGSAK)
  ENTRY(SIGSAK, "SIGSAK", "Secure attention"),
#endif
  ENTRY(0, NULL, NULL)
};

/* Translation table allocated and initialized at runtime.  Indexed by the
   signal value to find the equivalent symbolic value. */

static const char **signal_names;
static int num_signal_names = 0;

/* Translation table allocated and initialized at runtime, if it does not
   already exist in the host environment.  Indexed by the signal value to find
   the descriptive string.

   We don't export it for use in other modules because even though it has the
   same name, it differs from other implementations in that it is dynamically
   initialized rather than statically initialized. */

#ifndef HAVE_SYS_SIGLIST

static int sys_nsig;
static const char **sys_siglist;

#else

#ifdef NSIG
static int sys_nsig = NSIG;
#else
#ifdef _NSIG
static int sys_nsig = _NSIG;
#endif
#endif
extern const char * const sys_siglist[];

#endif


/*

NAME

	init_signal_tables -- initialize the name and message tables

SYNOPSIS

	static void init_signal_tables ();

DESCRIPTION

	Using the signal_table, which is initialized at compile time, generate
	the signal_names and the sys_siglist (if needed) tables, which are
	indexed at runtime by a specific signal value.

BUGS

	The initialization of the tables may fail under low memory conditions,
	in which case we don't do anything particularly useful, but we don't
	bomb either.  Who knows, it might succeed at a later point if we free
	some memory in the meantime.  In any case, the other routines know
	how to deal with lack of a table after trying to initialize it.  This
	may or may not be considered to be a bug, that we don't specifically
	warn about this particular failure mode.

*/

static void
init_signal_tables ()
{
  const struct signal_info *eip;
  int nbytes;

  /* If we haven't already scanned the signal_table once to find the maximum
     signal value, then go find it now. */

  if (num_signal_names == 0)
    {
      for (eip = signal_table; eip -> name != NULL; eip++)
	{
	  if (eip -> value >= num_signal_names)
	    {
	      num_signal_names = eip -> value + 1;
	    }
	}
    }

  /* Now attempt to allocate the signal_names table, zero it out, and then
     initialize it from the statically initialized signal_table. */

  if (signal_names == NULL)
    {
      nbytes = num_signal_names * sizeof (char *);
      if ((signal_names = (const char **) malloc (nbytes)) != NULL)
	{
	  memset (signal_names, 0, nbytes);
	  for (eip = signal_table; eip -> name != NULL; eip++)
	    {
	      signal_names[eip -> value] = eip -> name;
	    }
	}
    }

#ifndef HAVE_SYS_SIGLIST

  /* Now attempt to allocate the sys_siglist table, zero it out, and then
     initialize it from the statically initialized signal_table. */

  if (sys_siglist == NULL)
    {
      nbytes = num_signal_names * sizeof (char *);
      if ((sys_siglist = (const char **) malloc (nbytes)) != NULL)
	{
	  memset (sys_siglist, 0, nbytes);
	  sys_nsig = num_signal_names;
	  for (eip = signal_table; eip -> name != NULL; eip++)
	    {
	      sys_siglist[eip -> value] = eip -> msg;
	    }
	}
    }

#endif

}


/*

@deftypefn Extension int signo_max (void)

Returns the maximum signal value for which a corresponding symbolic
name or message is available.  Note that in the case where we use the
@code{sys_siglist} supplied by the system, it is possible for there to
be more symbolic names than messages, or vice versa.  In fact, the
manual page for @code{psignal(3b)} explicitly warns that one should
check the size of the table (@code{NSIG}) before indexing it, since
new signal codes may be added to the system before they are added to
the table.  Thus @code{NSIG} might be smaller than value implied by
the largest signo value defined in @code{<signal.h>}.

We return the maximum value that can be used to obtain a meaningful
symbolic name or message.

@end deftypefn

*/

int
signo_max ()
{
  int maxsize;

  if (signal_names == NULL)
    {
      init_signal_tables ();
    }
  maxsize = MAX (sys_nsig, num_signal_names);
  return (maxsize - 1);
}


/*

@deftypefn Supplemental {const char *} strsignal (int @var{signo})

Maps an signal number to an signal message string, the contents of
which are implementation defined.  On systems which have the external
variable @code{sys_siglist}, these strings will be the same as the
ones used by @code{psignal()}.

If the supplied signal number is within the valid range of indices for
the @code{sys_siglist}, but no message is available for the particular
signal number, then returns the string @samp{Signal @var{num}}, where
@var{num} is the signal number.

If the supplied signal number is not a valid index into
@code{sys_siglist}, returns @code{NULL}.

The returned string is only guaranteed to be valid only until the next
call to @code{strsignal}.

@end deftypefn

*/

#ifndef HAVE_STRSIGNAL

const char *
strsignal (signo)
  int signo;
{
  const char *msg;
  static char buf[32];

#ifndef HAVE_SYS_SIGLIST

  if (signal_names == NULL)
    {
      init_signal_tables ();
    }

#endif

  if ((signo < 0) || (signo >= sys_nsig))
    {
      /* Out of range, just return NULL */
      msg = NULL;
    }
  else if ((sys_siglist == NULL) || (sys_siglist[signo] == NULL))
    {
      /* In range, but no sys_siglist or no entry at this index. */
      sprintf (buf, "Signal %d", signo);
      msg = (const char *) buf;
    }
  else
    {
      /* In range, and a valid message.  Just return the message. */
      msg = (const char *) sys_siglist[signo];
    }
  
  return (msg);
}

#endif /* ! HAVE_STRSIGNAL */

/*

@deftypefn Extension {const char*} strsigno (int @var{signo})

Given an signal number, returns a pointer to a string containing the
symbolic name of that signal number, as found in @code{<signal.h>}.

If the supplied signal number is within the valid range of indices for
symbolic names, but no name is available for the particular signal
number, then returns the string @samp{Signal @var{num}}, where
@var{num} is the signal number.

If the supplied signal number is not within the range of valid
indices, then returns @code{NULL}.

The contents of the location pointed to are only guaranteed to be
valid until the next call to @code{strsigno}.

@end deftypefn

*/

const char *
strsigno (signo)
  int signo;
{
  const char *name;
  static char buf[32];

  if (signal_names == NULL)
    {
      init_signal_tables ();
    }

  if ((signo < 0) || (signo >= num_signal_names))
    {
      /* Out of range, just return NULL */
      name = NULL;
    }
  else if ((signal_names == NULL) || (signal_names[signo] == NULL))
    {
      /* In range, but no signal_names or no entry at this index. */
      sprintf (buf, "Signal %d", signo);
      name = (const char *) buf;
    }
  else
    {
      /* In range, and a valid name.  Just return the name. */
      name = signal_names[signo];
    }

  return (name);
}


/*

@deftypefn Extension int strtosigno (const char *@var{name})

Given the symbolic name of a signal, map it to a signal number.  If no
translation is found, returns 0.

@end deftypefn

*/

int
strtosigno (name)
     const char *name;
{
  int signo = 0;

  if (name != NULL)
    {
      if (signal_names == NULL)
	{
	  init_signal_tables ();
	}
      for (signo = 0; signo < num_signal_names; signo++)
	{
	  if ((signal_names[signo] != NULL) &&
	      (strcmp (name, signal_names[signo]) == 0))
	    {
	      break;
	    }
	}
      if (signo == num_signal_names)
	{
	  signo = 0;
	}
    }
  return (signo);
}


/*

@deftypefn Supplemental void psignal (unsigned @var{signo}, char *@var{message})

Print @var{message} to the standard error, followed by a colon,
followed by the description of the signal specified by @var{signo},
followed by a newline.

@end deftypefn

*/

#ifndef HAVE_PSIGNAL

void
psignal (signo, message)
  unsigned signo;
  char *message;
{
  if (signal_names == NULL)
    {
      init_signal_tables ();
    }
  if ((signo <= 0) || (signo >= sys_nsig))
    {
      fprintf (stderr, "%s: unknown signal\n", message);
    }
  else
    {
      fprintf (stderr, "%s: %s\n", message, sys_siglist[signo]);
    }
}

#endif	/* ! HAVE_PSIGNAL */


/* A simple little main that does nothing but print all the signal translations
   if MAIN is defined and this file is compiled and linked. */

#ifdef MAIN

#include <stdio.h>

int
main ()
{
  int signo;
  int maxsigno;
  const char *name;
  const char *msg;

  maxsigno = signo_max ();
  printf ("%d entries in names table.\n", num_signal_names);
  printf ("%d entries in messages table.\n", sys_nsig);
  printf ("%d is max useful index.\n", maxsigno);

  /* Keep printing values until we get to the end of *both* tables, not
     *either* table.  Note that knowing the maximum useful index does *not*
     relieve us of the responsibility of testing the return pointer for
     NULL. */

  for (signo = 0; signo <= maxsigno; signo++)
    {
      name = strsigno (signo);
      name = (name == NULL) ? "<NULL>" : name;
      msg = strsignal (signo);
      msg = (msg == NULL) ? "<NULL>" : msg;
      printf ("%-4d%-18s%s\n", signo, name, msg);
    }

  return 0;
}

#endif