/*
 * tclUnixInit.c --
 *
 *	Contains the Unix-specific interpreter initialization functions.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 * Copyright (c) 1999 by Scriptics Corporation.
 * All rights reserved.
 *
 * RCS: @(#) $Id: tclUnixInit.c,v 1.74 2007/11/10 03:41:23 das Exp $
 */

#include "tclInt.h"
#include <stddef.h>
#include <locale.h>
#ifdef HAVE_LANGINFO
#   include <langinfo.h>

 * Results:
 *	1 if there is enough stack space to continue; 0 if not.
 *
 * Side effects:
 *	None.
 *
 * Remark: Unused in the core, to be removed.
 *
 *----------------------------------------------------------------------
 */

int
TclpCheckStackSpace(void)
{
#ifdef TCL_NO_STACK_CHECK

    /*
     * This function was normally unimplemented on Unix platforms and this
     * implements old behavior, i.e. no stack checking performed.
     */

    return 1;

#else

    int localInt, *stackBound;

    TclpGetCStackParams(&stackBound);

    if (stackGrowsDown) {
	return (&localInt < stackBound) ;
    } else {
	return (&localInt > stackBound) ;
    }
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetStackParams --
 *
 *	Determine the stack params for the current thread: in which
 *	direction does the stack grow, and what is the stack lower (resp.
 *	upper) bound for safe invocation of a new command? This is used to
 *	cache the values needed for an efficient computation of
 *	TclpCheckStackSpace() when the interp is known.
 *
 * Results:
 *	Returns 1 if the stack grows down, in which case a stack lower bound
 *	is stored at stackBoundPtr. If the stack grows up, 0 is returned and
 *	an upper bound is stored at stackBoundPtr. If a bound cannot be
 *	determined NULL is stored at stackBoundPtr.
 *
 *----------------------------------------------------------------------
 */

int
TclpGetCStackParams(
    int **stackBoundPtr)
{
#ifdef TCL_NO_STACK_CHECK

	/*
	 * Not initialised!
	 */

	stackGrowsDown = StackGrowsDown(&localVar);
    }

    /*
     * The first time through, we record the "outermost" stack frame.
     */

    if (tsdPtr->outerVarPtr == NULL) {
	tsdPtr->outerVarPtr = &localVar;
    }

		STACK_DEBUG(("skipping stack checks with success\n"));
	}
	*stackBoundPtr = NULL;
	return 1; /* so that check always succeeds */
    }

    if (stackGrowsDown) {
	*stackBoundPtr = (int *) ((char *)tsdPtr->outerVarPtr -
		tsdPtr->stackSize);
    } else {
	*stackBoundPtr = (int *) ((char *)tsdPtr->outerVarPtr +
		tsdPtr->stackSize);
    }
    return stackGrowsDown;
#endif
}

int
StackGrowsDown(
    int *parent)
{
    int here;
    return (&here < parent);
}


/*
 *----------------------------------------------------------------------
 *
 * GetStackSize --
 *
 *	Discover what the stack size for the current thread/process actually