/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995--2015  The R Core Team.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, a copy is available at
 *  https://www.R-project.org/Licenses/
 */

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

#define R_USE_SIGNALS 1
#include <Defn.h>
#include <Internal.h>
/* -> Errormsg.h */
#include <Startup.h> /* rather cleanup ..*/
#include <Rconnections.h>
#include <Rinterface.h>
#include <R_ext/GraphicsEngine.h> /* for GEonExit */
#include <Rmath.h> /* for imax2 */
#include <R_ext/Print.h>

#ifndef min
#define min(a, b) (a<b?a:b)
#endif

/* Total line length, in chars, before splitting in warnings/errors */
#define LONGWARN 75

/*
Different values of inError are used to indicate different places
in the error handling.
*/
static int inError = 0;
static int inWarning = 0;
static int inPrintWarnings = 0;
static int immediateWarning = 0;
static int noBreakWarning = 0;

static void try_jump_to_restart(void);
// The next is crucial to the use of NORET attributes.
static void NORET
jump_to_top_ex(Rboolean, Rboolean, Rboolean, Rboolean, Rboolean);
static void signalInterrupt(void);
static char * R_ConciseTraceback(SEXP call, int skip);

/* Interface / Calling Hierarchy :

  R__stop()   -> do_error ->   errorcall --> (eventually) jump_to_top_ex
			 /
		    error

  R__warning()-> do_warning   -> warningcall -> if(warn >= 2) errorcall
			     /
		    warning /

  ErrorMessage()-> errorcall   (but with message from ErrorDB[])

  WarningMessage()-> warningcall (but with message from WarningDB[]).
*/

void NORET R_SignalCStackOverflow(intptr_t usage)
{
    /* We do need some stack space to process error recovery, so
       temporarily raise the limit.  We have 5% head room because we
       reduced R_CStackLimit to 95% of the initial value in
       setup_Rmainloop.
    */
    if (R_OldCStackLimit == 0) {
	R_OldCStackLimit = R_CStackLimit;
	R_CStackLimit = (uintptr_t) (R_CStackLimit / 0.95);
    }

    errorcall(R_NilValue, "C stack usage  %ld is too close to the limit",
	      usage);
    /* Do not translate this, to save stack space */
}

void (R_CheckStack)(void)
{
    int dummy;
    intptr_t usage = R_CStackDir * (R_CStackStart - (uintptr_t)&dummy);

    /* printf("usage %ld\n", usage); */
    if(R_CStackLimit != -1 && usage > ((intptr_t) R_CStackLimit))
	R_SignalCStackOverflow(usage);
}

void R_CheckStack2(size_t extra)
{
    int dummy;
    intptr_t usage = R_CStackDir * (R_CStackStart - (uintptr_t)&dummy);

    /* do it this way, as some compilers do usage + extra
       in unsigned arithmetic */
    usage += extra;
    if(R_CStackLimit != -1 && usage > ((intptr_t) R_CStackLimit))
	R_SignalCStackOverflow(usage);

}

void R_CheckUserInterrupt(void)
{
    R_CheckStack();

    /* Don't do any processing of interrupts, timing limits, or other
       asynchronous events if interrupts are suspended. */
    if (R_interrupts_suspended) return;

    /* This is the point where GUI systems need to do enough event
       processing to determine whether there is a user interrupt event
       pending.  Need to be careful not to do too much event
       processing though: if event handlers written in R are allowed
       to run at this point then we end up with concurrent R
       evaluations and that can cause problems until we have proper
       concurrency support. LT */

    R_ProcessEvents(); /* Also processes timing limits */
#ifndef Win32
    if (R_interrupts_pending) onintr();
#endif
}

void onintr()
{
    if (R_interrupts_suspended) {
	R_interrupts_pending = 1;
	return;
    }
    else R_interrupts_pending = 0;
    signalInterrupt();

    REprintf("\n");
    /* Attempt to run user error option, save a traceback, show
       warnings, and reset console; also stop at restart (try/browser)
       frames.  Not clear this is what we really want, but this
       preserves current behavior */
    jump_to_top_ex(TRUE, TRUE, TRUE, TRUE, FALSE);
}

/* SIGUSR1: save and quit
   SIGUSR2: save and quit, don't run .Last or on.exit().

   These do far more processing than is allowed in a signal handler ....
*/

RETSIGTYPE attribute_hidden onsigusr1(int dummy)
{
    if (R_interrupts_suspended) {
	/**** ought to save signal and handle after suspend */
	REprintf(_("interrupts suspended; signal ignored"));
	signal(SIGUSR1, onsigusr1);
	return;
    }

    inError = 1;

    if(R_CollectWarnings) PrintWarnings();

    R_ResetConsole();
    R_FlushConsole();
    R_ClearerrConsole();
    R_ParseError = 0;
    R_ParseErrorFile = NULL;
    R_ParseErrorMsg[0] = '\0';

    /* Bail out if there is a browser/try on the stack--do we really
       want this?  No, as from R 2.4.0
    try_jump_to_restart(); */

    /* Run all onexit/cend code on the stack (without stopping at
       intervening CTXT_TOPLEVEL's.  Since intervening CTXT_TOPLEVEL's
       get used by what are conceptually concurrent computations, this
       is a bit like telling all active threads to terminate and clean
       up on the way out. */
    R_run_onexits(NULL);

    R_CleanUp(SA_SAVE, 2, 1); /* quit, save,  .Last, status=2 */
}


RETSIGTYPE attribute_hidden onsigusr2(int dummy)
{
    inError = 1;

    if (R_interrupts_suspended) {
	/**** ought to save signal and handle after suspend */
	REprintf(_("interrupts suspended; signal ignored"));
	signal(SIGUSR2, onsigusr2);
	return;
    }

    if(R_CollectWarnings) PrintWarnings();

    R_ResetConsole();
    R_FlushConsole();
    R_ClearerrConsole();
    R_ParseError = 0;
    R_ParseErrorFile = NULL;
    R_ParseErrorMsg[0] = '\0';
    R_CleanUp(SA_SAVE, 0, 0);
}


static void setupwarnings(void)
{
    R_Warnings = allocVector(VECSXP, R_nwarnings);
    setAttrib(R_Warnings, R_NamesSymbol, allocVector(STRSXP, R_nwarnings));
}

/* Rvsnprintf: like vsnprintf, but guaranteed to null-terminate. */
#ifdef Win32
int trio_vsnprintf(char *buffer, size_t bufferSize, const char *format,
		   va_list args);

static int Rvsnprintf(char *buf, size_t size, const char  *format, va_list ap)
{
    int val;
    val = trio_vsnprintf(buf, size, format, ap);
    buf[size-1] = '\0';
    return val;
}
#else
static int Rvsnprintf(char *buf, size_t size, const char  *format, va_list ap)
{
    int val;
    val = vsnprintf(buf, size, format, ap);
    buf[size-1] = '\0';
    return val;
}
#endif

#define BUFSIZE 8192
static R_INLINE void RprintTrunc(char *buf)
{
    if(R_WarnLength < BUFSIZE - 20 && strlen(buf) == R_WarnLength) {
	strcat(buf, " ");
	strcat(buf, _("[... truncated]"));
    }
}

void warning(const char *format, ...)
{
    char buf[BUFSIZE], *p;
    RCNTXT *c = R_GlobalContext;

    va_list(ap);
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength+1), format, ap);
    va_end(ap);
    p = buf + strlen(buf) - 1;
    if(strlen(buf) > 0 && *p == '\n') *p = '\0';
    RprintTrunc(buf);
    if (c && (c->callflag & CTXT_BUILTIN)) c = c->nextcontext;
    warningcall(c ? c->call : R_NilValue, "%s", buf);
}

/* declarations for internal condition handling */

static void vsignalError(SEXP call, const char *format, va_list ap);
static void vsignalWarning(SEXP call, const char *format, va_list ap);
static void NORET invokeRestart(SEXP, SEXP);

static void reset_inWarning(void *data)
{
    inWarning = 0;
}

#include <rlocale.h>

static int wd(const char * buf)
{
    int nc = (int) mbstowcs(NULL, buf, 0), nw;
    if(nc > 0 && nc < 2000) {
	wchar_t wc[2000];
	mbstowcs(wc, buf, nc + 1);
	nw = Ri18n_wcswidth(wc, 2147483647);
	return (nw < 1) ? nc : nw;
    }
    return nc;
}

static void vwarningcall_dflt(SEXP call, const char *format, va_list ap)
{
    int w;
    SEXP names, s;
    const char *dcall;
    char buf[BUFSIZE];
    RCNTXT *cptr;
    RCNTXT cntxt;

    if (inWarning)
	return;

    s = GetOption1(install("warning.expression"));
    if( s != R_NilValue ) {
	if( !isLanguage(s) &&  ! isExpression(s) )
	    error(_("invalid option \"warning.expression\""));
	cptr = R_GlobalContext;
	while ( !(cptr->callflag & CTXT_FUNCTION) && cptr->callflag )
	    cptr = cptr->nextcontext;
	eval(s, cptr->cloenv);
	return;
    }

    w = asInteger(GetOption1(install("warn")));

    if( w == NA_INTEGER ) /* set to a sensible value */
	w = 0;

    if( w <= 0 && immediateWarning ) w = 1;

    if( w < 0 || inWarning || inError) /* ignore if w<0 or already in here*/
	return;

    /* set up a context which will restore inWarning if there is an exit */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_BaseEnv, R_BaseEnv,
		 R_NilValue, R_NilValue);
    cntxt.cend = &reset_inWarning;

    inWarning = 1;

    if(w >= 2) { /* make it an error */
	Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
	RprintTrunc(buf);
	inWarning = 0; /* PR#1570 */
	errorcall(call, _("(converted from warning) %s"), buf);
    }
    else if(w == 1) {	/* print as they happen */
	char *tr;
	if( call != R_NilValue ) {
	    dcall = CHAR(STRING_ELT(deparse1s(call), 0));
	} else dcall = "";
	Rvsnprintf(buf, min(BUFSIZE, R_WarnLength+1), format, ap);
	RprintTrunc(buf);

	if(dcall[0] == '\0') REprintf(_("Warning:"));
	else {
	    REprintf(_("Warning in %s :"), dcall);
	    if(!(noBreakWarning ||
		 ( mbcslocale && 18 + wd(dcall) + wd(buf) <= LONGWARN) ||
		 (!mbcslocale && 18 + strlen(dcall) + strlen(buf) <= LONGWARN)))
		REprintf("\n ");
	}
	REprintf(" %s\n", buf);
	if(R_ShowWarnCalls && call != R_NilValue) {
	    tr = R_ConciseTraceback(call, 0);
	    if (strlen(tr)) {REprintf(_("Calls:")); REprintf(" %s\n", tr);}
	}
    }
    else if(w == 0) {	/* collect them */
	if(!R_CollectWarnings) setupwarnings();
	if(R_CollectWarnings < R_nwarnings) {
	    SET_VECTOR_ELT(R_Warnings, R_CollectWarnings, call);
	    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength+1), format, ap);
	    RprintTrunc(buf);
	    if(R_ShowWarnCalls && call != R_NilValue) {
		char *tr =  R_ConciseTraceback(call, 0);
		size_t nc = strlen(tr);
		if (nc && nc + (int)strlen(buf) + 8 < BUFSIZE) {
		    strcat(buf, "\n");
		    strcat(buf, _("Calls:"));
		    strcat(buf, " ");
		    strcat(buf, tr);
		}
	    }
	    names = CAR(ATTRIB(R_Warnings));
	    SET_STRING_ELT(names, R_CollectWarnings++, mkChar(buf));
	}
    }
    /* else:  w <= -1 */
    endcontext(&cntxt);
    inWarning = 0;
}

static void warningcall_dflt(SEXP call, const char *format,...)
{
    va_list(ap);

    va_start(ap, format);
    vwarningcall_dflt(call, format, ap);
    va_end(ap);
}

void warningcall(SEXP call, const char *format, ...)
{
    va_list(ap);
    va_start(ap, format);
    vsignalWarning(call, format, ap);
    va_end(ap);
}

void warningcall_immediate(SEXP call, const char *format, ...)
{
    va_list(ap);

    immediateWarning = 1;
    va_start(ap, format);
    vsignalWarning(call, format, ap);
    va_end(ap);
    immediateWarning = 0;
}

static void cleanup_PrintWarnings(void *data)
{
    if (R_CollectWarnings) {
	R_CollectWarnings = 0;
	R_Warnings = R_NilValue;
	REprintf(_("Lost warning messages\n"));
    }
    inPrintWarnings = 0;
}

attribute_hidden
void PrintWarnings(void)
{
    int i;
    char *header;
    SEXP names, s, t;
    RCNTXT cntxt;

    if (R_CollectWarnings == 0)
	return;
    else if (inPrintWarnings) {
	if (R_CollectWarnings) {
	    R_CollectWarnings = 0;
	    R_Warnings = R_NilValue;
	    REprintf(_("Lost warning messages\n"));
	}
	return;
    }

    /* set up a context which will restore inPrintWarnings if there is
       an exit */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_BaseEnv, R_BaseEnv,
		 R_NilValue, R_NilValue);
    cntxt.cend = &cleanup_PrintWarnings;

    inPrintWarnings = 1;
    header = ngettext("Warning message:", "Warning messages:",
		      R_CollectWarnings);
    if( R_CollectWarnings == 1 ) {
	REprintf("%s\n", header);
	names = CAR(ATTRIB(R_Warnings));
	if( VECTOR_ELT(R_Warnings, 0) == R_NilValue )
	    REprintf("%s \n", CHAR(STRING_ELT(names, 0)));
	else {
	    const char *dcall, *msg = CHAR(STRING_ELT(names, 0));
	    dcall = CHAR(STRING_ELT(deparse1s(VECTOR_ELT(R_Warnings, 0)), 0));
	    REprintf(_("In %s :"), dcall);
	    if (mbcslocale) {
		int msgline1;
		char *p = strchr(msg, '\n');
		if (p) {
		    *p = '\0';
		    msgline1 = wd(msg);
		    *p = '\n';
		} else msgline1 = wd(msg);
		if (6 + wd(dcall) + msgline1 > LONGWARN) REprintf("\n ");
	    } else {
		size_t msgline1 = strlen(msg);
		char *p = strchr(msg, '\n');
		if (p) msgline1 = (int)(p - msg);
		if (6 + strlen(dcall) + msgline1 > LONGWARN) REprintf("\n ");
	    }
	    REprintf(" %s\n", msg);
	}
    } else if( R_CollectWarnings <= 10 ) {
	REprintf("%s\n", header);
	names = CAR(ATTRIB(R_Warnings));
	for(i = 0; i < R_CollectWarnings; i++) {
	    if( VECTOR_ELT(R_Warnings, i) == R_NilValue ) {
		REprintf("%d: %s \n", i+1, CHAR(STRING_ELT(names, i)));
	    } else {
		const char *dcall, *msg = CHAR(STRING_ELT(names, i));
		dcall = CHAR(STRING_ELT(deparse1s(VECTOR_ELT(R_Warnings, i)), 0));
		REprintf("%d: ", i + 1);
		REprintf(_("In %s :"), dcall);
		if (mbcslocale) {
		    int msgline1;
		    char *p = strchr(msg, '\n');
		    if (p) {
			*p = '\0';
			msgline1 = wd(msg);
			*p = '\n';
		    } else msgline1 = wd(msg);
		    if (10 + wd(dcall) + msgline1 > LONGWARN) {
			REprintf("\n ");
		    }
		} else {
		    size_t msgline1 = strlen(msg);
		    char *p = strchr(msg, '\n');
		    if (p) msgline1 = (int)(p - msg);
		    if (10 + strlen(dcall) + msgline1 > LONGWARN) {
			REprintf("\n ");
		    }
		}
		REprintf(" %s\n", msg);
	    }
	}
    } else {
	if (R_CollectWarnings < R_nwarnings)
	    REprintf(ngettext("There was %d warning (use warnings() to see it)",
			      "There were %d warnings (use warnings() to see them)",
			      R_CollectWarnings),
		     R_CollectWarnings);
	else
	    REprintf(_("There were %d or more warnings (use warnings() to see the first %d)"),
		     R_nwarnings, R_nwarnings);
	REprintf("\n");
    }
    /* now truncate and install last.warning */
    PROTECT(s = allocVector(VECSXP, R_CollectWarnings));
    PROTECT(t = allocVector(STRSXP, R_CollectWarnings));
    names = CAR(ATTRIB(R_Warnings));
    for(i = 0; i < R_CollectWarnings; i++) {
	SET_VECTOR_ELT(s, i, VECTOR_ELT(R_Warnings, i));
	SET_STRING_ELT(t, i, STRING_ELT(names, i));
    }
    setAttrib(s, R_NamesSymbol, t);
    SET_SYMVALUE(install("last.warning"), s);
    UNPROTECT(2);

    endcontext(&cntxt);

    inPrintWarnings = 0;
    R_CollectWarnings = 0;
    R_Warnings = R_NilValue;
    return;
}

/* Return a constructed source location (e.g. filename#123) from a srcref.  If the srcref
   is not valid "" will be returned.
*/

static SEXP GetSrcLoc(SEXP srcref)
{
    SEXP sep, line, result, srcfile;
    if (TYPEOF(srcref) != INTSXP || length(srcref) < 4)
	return ScalarString(mkChar(""));

    PROTECT(srcref);
    PROTECT(srcfile = R_GetSrcFilename(srcref));
    SEXP e2 = PROTECT(lang2( install("basename"), srcfile));
    PROTECT(srcfile = eval(e2, R_BaseEnv ) );
    PROTECT(sep = ScalarString(mkChar("#")));
    PROTECT(line = ScalarInteger(INTEGER(srcref)[0]));
    SEXP e = PROTECT(lang4( install("paste0"), srcfile, sep, line ));
    result = eval(e, R_BaseEnv );
    UNPROTECT(7);
    return result;
}

static char errbuf[BUFSIZE];

const char *R_curErrorBuf() {
    return (const char *)errbuf;
}

/* temporary hook to allow experimenting with alternate error mechanisms */
static void (*R_ErrorHook)(SEXP, char *) = NULL;

static void restore_inError(void *data)
{
    int *poldval = (int *) data;
    inError = *poldval;
    R_Expressions = R_Expressions_keep;
}

static void NORET
verrorcall_dflt(SEXP call, const char *format, va_list ap)
{
    RCNTXT cntxt;
    char *p, *tr;
    int oldInError;

    if (inError) {
	/* fail-safe handler for recursive errors */
	if(inError == 3) {
	     /* Can REprintf generate an error? If so we should guard for it */
	    REprintf(_("Error during wrapup: "));
	    /* this does NOT try to print the call since that could
	       cause a cascade of error calls */
	    Rvsnprintf(errbuf, sizeof(errbuf), format, ap);
	    REprintf("%s\n", errbuf);
	}
	if (R_Warnings != R_NilValue) {
	    R_CollectWarnings = 0;
	    R_Warnings = R_NilValue;
	    REprintf(_("Lost warning messages\n"));
	}
	R_Expressions = R_Expressions_keep;
	jump_to_top_ex(FALSE, FALSE, FALSE, FALSE, FALSE);
    }

    /* set up a context to restore inError value on exit */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_BaseEnv, R_BaseEnv,
		 R_NilValue, R_NilValue);
    cntxt.cend = &restore_inError;
    cntxt.cenddata = &oldInError;
    oldInError = inError;
    inError = 1;

    if(call != R_NilValue) {
	char tmp[BUFSIZE], tmp2[BUFSIZE];
	char *head = _("Error in "), *tail = "\n  ";
	SEXP srcloc = R_NilValue; // -Wall
	size_t len = 0;	// indicates if srcloc has been set
	int protected = 0, skip = NA_INTEGER;
	SEXP opt = GetOption1(install("show.error.locations"));
	if (!isNull(opt)) {
	    if (TYPEOF(opt) == STRSXP && length(opt) == 1) {
		if (pmatch(ScalarString(mkChar("top")), opt, 0)) skip = 0;
		else if (pmatch(ScalarString(mkChar("bottom")), opt, 0)) skip = -1;
	    } else if (TYPEOF(opt) == LGLSXP)
		skip = asLogical(opt) == 1 ? 0 : NA_INTEGER;
	    else
		skip = asInteger(opt);
	}

	const char *dcall = CHAR(STRING_ELT(deparse1s(call), 0));
	snprintf(tmp2, BUFSIZE,  "%s", head);
	if (skip != NA_INTEGER) {
	    PROTECT(srcloc = GetSrcLoc(R_GetCurrentSrcref(skip)));
	    protected++;
	    len = strlen(CHAR(STRING_ELT(srcloc, 0)));
	    if (len)
		snprintf(tmp2, BUFSIZE,  _("Error in %s (from %s) : "),
			 dcall, CHAR(STRING_ELT(srcloc, 0)));
	}

	Rvsnprintf(tmp, min(BUFSIZE, R_WarnLength) - strlen(head), format, ap);
	if (strlen(tmp2) + strlen(tail) + strlen(tmp) < BUFSIZE) {
	    if(len) snprintf(errbuf, BUFSIZE,
			     _("Error in %s (from %s) : "),
			     dcall, CHAR(STRING_ELT(srcloc, 0)));
	    else snprintf(errbuf, BUFSIZE,  _("Error in %s : "), dcall);
	    if (mbcslocale) {
		int msgline1;
		char *p = strchr(tmp, '\n');
		if (p) {
		    *p = '\0';
		    msgline1 = wd(tmp);
		    *p = '\n';
		} else msgline1 = wd(tmp);
		if (14 + wd(dcall) + msgline1 > LONGWARN)
		    strcat(errbuf, tail);
	    } else {
		size_t msgline1 = strlen(tmp);
		char *p = strchr(tmp, '\n');
		if (p) msgline1 = (int)(p - tmp);
		if (14 + strlen(dcall) + msgline1 > LONGWARN)
		    strcat(errbuf, tail);
	    }
	    strcat(errbuf, tmp);
	} else {
	    snprintf(errbuf, BUFSIZE, _("Error: "));
	    strcat(errbuf, tmp); // FIXME
	}
	UNPROTECT(protected);
    }
    else {
	snprintf(errbuf, BUFSIZE, _("Error: "));
	p = errbuf + strlen(errbuf);
	Rvsnprintf(p, min(BUFSIZE, R_WarnLength) - strlen(errbuf), format, ap);
    }

    p = errbuf + strlen(errbuf) - 1;
    if(*p != '\n') strcat(errbuf, "\n");

    if(R_ShowErrorCalls && call != R_NilValue) {  /* assume we want to avoid deparse */
	tr = R_ConciseTraceback(call, 0);
	size_t nc = strlen(tr);
	if (nc && nc + strlen(errbuf) + 8 < BUFSIZE) {
	    strcat(errbuf, _("Calls:"));
	    strcat(errbuf, " ");
	    strcat(errbuf, tr);
	    strcat(errbuf, "\n");
	}
    }
    if (R_ShowErrorMessages) REprintf("%s", errbuf);

    if( R_ShowErrorMessages && R_CollectWarnings ) {
	REprintf(_("In addition: "));
	PrintWarnings();
    }

    jump_to_top_ex(TRUE, TRUE, TRUE, TRUE, FALSE);

    /* not reached */
    endcontext(&cntxt);
    inError = oldInError;
}

static void NORET errorcall_dflt(SEXP call, const char *format,...)
{
    va_list(ap);

    va_start(ap, format);
    verrorcall_dflt(call, format, ap);
    va_end(ap);
}

void NORET errorcall(SEXP call, const char *format,...)
{
    va_list(ap);

    va_start(ap, format);
    vsignalError(call, format, ap);
    va_end(ap);

    if (R_ErrorHook != NULL) {
	char buf[BUFSIZE];
	void (*hook)(SEXP, char *) = R_ErrorHook;
	R_ErrorHook = NULL; /* to avoid recursion */
	va_start(ap, format);
	Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
	va_end(ap);
	hook(call, buf);
    }

    va_start(ap, format);
    verrorcall_dflt(call, format, ap);
    va_end(ap);
}

SEXP attribute_hidden do_geterrmessage(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP res;

    checkArity(op, args);
    PROTECT(res = allocVector(STRSXP, 1));
    SET_STRING_ELT(res, 0, mkChar(errbuf));
    UNPROTECT(1);
    return res;
}

void error(const char *format, ...)
{
    char buf[BUFSIZE];
    RCNTXT *c = R_GlobalContext;

    va_list(ap);
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
    va_end(ap);
    /* This can be called before R_GlobalContext is defined, so... */
    /* If profiling is on, this can be a CTXT_BUILTIN */
    if (c && (c->callflag & CTXT_BUILTIN)) c = c->nextcontext;
    errorcall(c ? c->call : R_NilValue, "%s", buf);
}

static void try_jump_to_restart(void)
{
    SEXP list;

    for (list = R_RestartStack; list != R_NilValue; list = CDR(list)) {
	SEXP restart = CAR(list);
	if (TYPEOF(restart) == VECSXP && LENGTH(restart) > 1) {
	    SEXP name = VECTOR_ELT(restart, 0);
	    if (TYPEOF(name) == STRSXP && LENGTH(name) == 1) {
		const char *cname = CHAR(STRING_ELT(name, 0));
		if (! strcmp(cname, "browser") ||
		    ! strcmp(cname, "tryRestart") ||
		    ! strcmp(cname, "abort")) /**** move abort eventually? */
		    invokeRestart(restart, R_NilValue);
	    }
	}
    }
}

/* Unwind the call stack in an orderly fashion */
/* calling the code installed by on.exit along the way */
/* and finally longjmping to the innermost TOPLEVEL context */

static void jump_to_top_ex(Rboolean traceback,
			   Rboolean tryUserHandler,
			   Rboolean processWarnings,
			   Rboolean resetConsole,
			   Rboolean ignoreRestartContexts)
{
    RCNTXT cntxt;
    SEXP s;
    int haveHandler, oldInError;

    /* set up a context to restore inError value on exit */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_BaseEnv, R_BaseEnv,
		 R_NilValue, R_NilValue);
    cntxt.cend = &restore_inError;
    cntxt.cenddata = &oldInError;

    oldInError = inError;

    haveHandler = FALSE;

    /* don't use options("error") when handling a C stack overflow */
    if (R_OldCStackLimit == 0 && tryUserHandler && inError < 3) {
	if (! inError)
	    inError = 1;

	/* now see if options("error") is set */
	s = GetOption1(install("error"));
	haveHandler = ( s != R_NilValue );
	if (haveHandler) {
	    if( !isLanguage(s) &&  ! isExpression(s) )  /* shouldn't happen */
		REprintf(_("invalid option \"error\"\n"));
	    else {
		inError = 3;
		if (isLanguage(s))
		    eval(s, R_GlobalEnv);
		else /* expression */
		    {
			int i, n = LENGTH(s);
			for (i = 0 ; i < n ; i++)
			    eval(VECTOR_ELT(s, i), R_GlobalEnv);
		    }
		inError = oldInError;
	    }
	}
	inError = oldInError;
    }

    /* print warnings if there are any left to be printed */
    if( processWarnings && R_CollectWarnings )
	PrintWarnings();

    /* reset some stuff--not sure (all) this belongs here */
    if (resetConsole) {
	R_ResetConsole();
	R_FlushConsole();
	R_ClearerrConsole();
	R_ParseError = 0;
	R_ParseErrorFile = NULL;
	R_ParseErrorMsg[0] = '\0';
    }

    /*
     * Reset graphics state
     */
    GEonExit();

    /* WARNING: If oldInError > 0 ABSOLUTELY NO ALLOCATION can be
       triggered after this point except whatever happens in writing
       the traceback.  The error could be an out of memory error and
       any allocation could result in an infinite-loop condition. All
       you can do is reset things and exit.  */

    /* jump to a browser/try if one is on the stack */
    if (! ignoreRestartContexts)
	try_jump_to_restart();
    /* at this point, i.e. if we have not exited in
       try_jump_to_restart, we are heading for R_ToplevelContext */

    /* only run traceback if we are not going to bail out of a
       non-interactive session */
    if (R_Interactive || haveHandler) {
	/* write traceback if requested, unless we're already doing it
	   or there is an inconsistency between inError and oldInError
	   (which should not happen) */
	if (traceback && inError < 2 && inError == oldInError) {
	    inError = 2;
	    PROTECT(s = R_GetTraceback(0));
	    SET_SYMVALUE(install(".Traceback"), s);
	    /* should have been defineVar
	       setVar(install(".Traceback"), s, R_GlobalEnv); */
	    UNPROTECT(1);
	    inError = oldInError;
	}
    }

    R_jumpctxt(R_ToplevelContext, 0, NULL);
}

void NORET jump_to_toplevel()
{
    /* no traceback, no user error option; for now, warnings are
       printed here and console is reset -- eventually these should be
       done after arriving at the jump target.  Now ignores
       try/browser frames--it really is a jump to toplevel */
    jump_to_top_ex(FALSE, FALSE, TRUE, TRUE, TRUE);
}

/* #define DEBUG_GETTEXT 1 */

/* gettext(domain, string) */
SEXP attribute_hidden do_gettext(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
#ifdef ENABLE_NLS
    const char *domain = "", *cfn;
    char *buf;
    SEXP ans, string = CADR(args);
    int i, n = LENGTH(string);

    checkArity(op, args);
    if(isNull(string) || !n) return string;

    if(!isString(string)) errorcall(call, _("invalid '%s' value"), "string");

    if(isNull(CAR(args))) {
	RCNTXT *cptr;
	SEXP rho = R_BaseEnv;
	for (cptr = R_GlobalContext->nextcontext;
	     cptr != NULL && cptr->callflag != CTXT_TOPLEVEL;
	     cptr = cptr->nextcontext)
	    if (cptr->callflag & CTXT_FUNCTION) {
		/* stop() etc have internal call to .makeMessage */
		cfn = CHAR(STRING_ELT(deparse1s(CAR(cptr->call)), 0));
		if(streql(cfn, "stop") || streql(cfn, "warning")
		   || streql(cfn, "message")) continue;
		rho = cptr->cloenv;
	    }
	while(rho != R_EmptyEnv) {
	    if (rho == R_GlobalEnv) break;
	    else if (R_IsNamespaceEnv(rho)) {
		domain = translateChar(STRING_ELT(R_NamespaceEnvSpec(rho), 0));
		break;
	    }
	    rho = CDR(rho);
	}
	if(strlen(domain)) {
	    size_t len = strlen(domain)+3;
	    R_CheckStack2(len);
	    buf = (char *) alloca(len);
	    snprintf(buf, len, "R-%s", domain);
	    domain = buf;
	}
    } else if(isString(CAR(args)))
	domain = translateChar(STRING_ELT(CAR(args),0));
    else if(isLogical(CAR(args)) && LENGTH(CAR(args)) == 1 && LOGICAL(CAR(args))[0] == NA_LOGICAL) ;
    else errorcall(call, _("invalid '%s' value"), "domain");

    if(strlen(domain)) {
	PROTECT(ans = allocVector(STRSXP, n));
	for(i = 0; i < n; i++) {
	    int ihead = 0, itail = 0;
	    const char * This = translateChar(STRING_ELT(string, i));
	    char *tmp, *head = NULL, *tail = NULL, *p, *tr;
	    R_CheckStack2(strlen(This) + 1);
	    tmp = (char *) alloca(strlen(This) + 1);
	    strcpy(tmp, This);
	    /* strip leading and trailing white spaces and
	       add back after translation */
	    for(p = tmp;
		*p && (*p == ' ' || *p == '\t' || *p == '\n');
		p++, ihead++) ;
	    if(ihead > 0) {
		R_CheckStack2(ihead + 1);
		head = (char *) alloca(ihead + 1);
		strncpy(head, tmp, ihead);
		head[ihead] = '\0';
		tmp += ihead;
		}
	    if(strlen(tmp))
		for(p = tmp+strlen(tmp)-1;
		    p >= tmp && (*p == ' ' || *p == '\t' || *p == '\n');
		    p--, itail++) ;
	    if(itail > 0) {
		R_CheckStack2(itail + 1);
		tail = (char *) alloca(itail + 1);
		strcpy(tail, tmp+strlen(tmp)-itail);
		tmp[strlen(tmp)-itail] = '\0';
	    }
	    if(strlen(tmp)) {
#ifdef DEBUG_GETTEXT
		REprintf("translating '%s' in domain '%s'\n", tmp, domain);
#endif
		tr = dgettext(domain, tmp);
		R_CheckStack2(strlen(tr) + ihead + itail + 1);
		tmp = (char *) alloca(strlen(tr) + ihead + itail + 1);
		tmp[0] ='\0';
		if(ihead > 0) strcat(tmp, head);
		strcat(tmp, tr);
		if(itail > 0) strcat(tmp, tail);
		SET_STRING_ELT(ans, i, mkChar(tmp));
	    } else
		SET_STRING_ELT(ans, i, mkChar(This));
	}
	UNPROTECT(1);
	return ans;
    } else return CADR(args);
#else
    return CADR(args);
#endif
}

/* ngettext(n, msg1, msg2, domain) */
SEXP attribute_hidden do_ngettext(SEXP call, SEXP op, SEXP args, SEXP rho)
{
#ifdef ENABLE_NLS
    const char *domain = "", *cfn;;
    char *buf;
    SEXP ans, sdom = CADDDR(args);
#endif
    SEXP msg1 = CADR(args), msg2 = CADDR(args);
    int n = asInteger(CAR(args));

    checkArity(op, args);
    if(n == NA_INTEGER || n < 0) error(_("invalid '%s' argument"), "n");
    if(!isString(msg1) || LENGTH(msg1) != 1)
	error(_("'%s' must be a character string"), "msg1");
    if(!isString(msg2) || LENGTH(msg2) != 1)
	error(_("'%s' must be a character string"), "msg2");

#ifdef ENABLE_NLS
    if(isNull(sdom)) {
	RCNTXT *cptr;
	SEXP rho = R_BaseEnv;
	for (cptr = R_GlobalContext->nextcontext;
	     cptr != NULL && cptr->callflag != CTXT_TOPLEVEL;
	     cptr = cptr->nextcontext)
	    if (cptr->callflag & CTXT_FUNCTION) {
		/* stop() etc have internal call to .makeMessage */
		cfn = CHAR(STRING_ELT(deparse1s(CAR(cptr->call)), 0));
		if(streql(cfn, "stop") || streql(cfn, "warning")
		   || streql(cfn, "message")) continue;
		rho = cptr->cloenv;
	    }
	while(rho != R_EmptyEnv) {
	    if (rho == R_GlobalEnv) break;
	    else if (R_IsNamespaceEnv(rho)) {
		domain = translateChar(STRING_ELT(R_NamespaceEnvSpec(rho), 0));
		break;
	    }
	    rho = CDR(rho);
	}
	if(strlen(domain)) {
	    size_t len = strlen(domain)+3;
	    R_CheckStack2(len);
	    buf = (char *) alloca(len);
	    snprintf(buf, len, "R-%s", domain);
	    domain = buf;
	}
    } else if(isString(sdom))
	domain = CHAR(STRING_ELT(sdom,0));
    else if(isLogical(sdom) && LENGTH(sdom) == 1 && LOGICAL(sdom)[0] == NA_LOGICAL) ;
    else errorcall(call, _("invalid '%s' value"), "domain");

    /* libintl seems to malfunction if given a message of "" */
    if(strlen(domain) && length(STRING_ELT(msg1, 0))) {
	char *fmt = dngettext(domain,
			      translateChar(STRING_ELT(msg1, 0)),
			      translateChar(STRING_ELT(msg2, 0)),
			      n);
	PROTECT(ans = mkString(fmt));
	UNPROTECT(1);
	return ans;
    } else
#endif
	return n == 1 ? msg1 : msg2;
}


/* bindtextdomain(domain, dirname) */
SEXP attribute_hidden do_bindtextdomain(SEXP call, SEXP op, SEXP args, SEXP rho)
{
#ifdef ENABLE_NLS
    char *res;

    checkArity(op, args);
    if(!isString(CAR(args)) || LENGTH(CAR(args)) != 1)
	errorcall(call, _("invalid '%s' value"), "domain");
    if(isNull(CADR(args))) {
	res = bindtextdomain(translateChar(STRING_ELT(CAR(args),0)), NULL);
    } else {
	if(!isString(CADR(args)) || LENGTH(CADR(args)) != 1)
	    errorcall(call, _("invalid '%s' value"), "dirname");
	res = bindtextdomain(translateChar(STRING_ELT(CAR(args),0)),
			     translateChar(STRING_ELT(CADR(args),0)));
    }
    if(res) return mkString(res);
    /* else this failed */
#endif
    return R_NilValue;
}

static SEXP findCall(void)
{
    RCNTXT *cptr;
    for (cptr = R_GlobalContext->nextcontext;
	 cptr != NULL && cptr->callflag != CTXT_TOPLEVEL;
	 cptr = cptr->nextcontext)
	if (cptr->callflag & CTXT_FUNCTION)
	    return cptr->call;
    return R_NilValue;
}

SEXP attribute_hidden NORET do_stop(SEXP call, SEXP op, SEXP args, SEXP rho)
{
/* error(.) : really doesn't return anything; but all do_foo() must be SEXP */
    SEXP c_call;
    checkArity(op, args);

    if(asLogical(CAR(args))) /* find context -> "Error in ..:" */
	c_call = findCall();
    else
	c_call = R_NilValue;

    args = CDR(args);

    if (CAR(args) != R_NilValue) { /* message */
      SETCAR(args, coerceVector(CAR(args), STRSXP));
      if(!isValidString(CAR(args)))
	  errorcall(c_call, _(" [invalid string in stop(.)]"));
      errorcall(c_call, "%s", translateChar(STRING_ELT(CAR(args), 0)));
    }
    else
      errorcall(c_call, "");
    /* never called: */
}

SEXP attribute_hidden do_warning(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP c_call;
    checkArity(op, args);

    if(asLogical(CAR(args))) /* find context -> "... in: ..:" */
	c_call = findCall();
    else
	c_call = R_NilValue;

    args = CDR(args);
    if(asLogical(CAR(args))) { /* immediate = TRUE */
	immediateWarning = 1;
    } else
	immediateWarning = 0;
    args = CDR(args);
    if(asLogical(CAR(args))) { /* noBreak = TRUE */
	noBreakWarning = 1;
    } else
	noBreakWarning = 0;
    args = CDR(args);
    if (CAR(args) != R_NilValue) {
	SETCAR(args, coerceVector(CAR(args), STRSXP));
	if(!isValidString(CAR(args)))
	    warningcall(c_call, _(" [invalid string in warning(.)]"));
	else
	    warningcall(c_call, "%s", translateChar(STRING_ELT(CAR(args), 0)));
    }
    else
	warningcall(c_call, "");
    immediateWarning = 0; /* reset to internal calls */
    noBreakWarning = 0;

    return CAR(args);
}

/* Error recovery for incorrect argument count error. */
attribute_hidden
void NORET WrongArgCount(const char *s)
{
    error(_("incorrect number of arguments to \"%s\""), s);
}


void NORET UNIMPLEMENTED(const char *s)
{
    error(_("unimplemented feature in %s"), s);
}

/* ERROR_.. codes in Errormsg.h */
static struct {
    const R_ERROR code;
    const char* const format;
}
const ErrorDB[] = {
    { ERROR_NUMARGS,		N_("invalid number of arguments")	},
    { ERROR_ARGTYPE,		N_("invalid argument type")		},

    { ERROR_TSVEC_MISMATCH,	N_("time-series/vector length mismatch")},
    { ERROR_INCOMPAT_ARGS,	N_("incompatible arguments")		},

    { ERROR_UNIMPLEMENTED,	N_("unimplemented feature in %s")	},
    { ERROR_UNKNOWN,		N_("unknown error (report this!)")	}
};

static struct {
    R_WARNING code;
    char* format;
}
WarningDB[] = {
    { WARNING_coerce_NA,	N_("NAs introduced by coercion")	},
    { WARNING_coerce_INACC,	N_("inaccurate integer conversion in coercion")},
    { WARNING_coerce_IMAG,	N_("imaginary parts discarded in coercion") },

    { WARNING_UNKNOWN,		N_("unknown warning (report this!)")	},
};


attribute_hidden
void NORET ErrorMessage(SEXP call, int which_error, ...)
{
    int i;
    char buf[BUFSIZE];
    va_list(ap);

    i = 0;
    while(ErrorDB[i].code != ERROR_UNKNOWN) {
	if (ErrorDB[i].code == which_error)
	    break;
	i++;
    }

    va_start(ap, which_error);
    Rvsnprintf(buf, BUFSIZE, _(ErrorDB[i].format), ap);
    va_end(ap);
    errorcall(call, "%s", buf);
}

attribute_hidden
void WarningMessage(SEXP call, R_WARNING which_warn, ...)
{
    int i;
    char buf[BUFSIZE];
    va_list(ap);

    i = 0;
    while(WarningDB[i].code != WARNING_UNKNOWN) {
	if (WarningDB[i].code == which_warn)
	    break;
	i++;
    }

    va_start(ap, which_warn);
    Rvsnprintf(buf, BUFSIZE, _(WarningDB[i].format), ap);
    va_end(ap);
    warningcall(call, "%s", buf);
}

#ifdef UNUSED
/* temporary hook to allow experimenting with alternate warning mechanisms */
static void (*R_WarningHook)(SEXP, char *) = NULL;

void R_SetWarningHook(void (*hook)(SEXP, char *))
{
    R_WarningHook = hook;
}

void R_SetErrorHook(void (*hook)(SEXP, char *))
{
    R_ErrorHook = hook;
}

void R_ReturnOrRestart(SEXP val, SEXP env, Rboolean restart)
{
    int mask;
    RCNTXT *c;

    mask = CTXT_BROWSER | CTXT_FUNCTION;

    for (c = R_GlobalContext; c; c = c->nextcontext) {
	if (c->callflag & mask && c->cloenv == env)
	    findcontext(mask, env, val);
	else if (restart && IS_RESTART_BIT_SET(c->callflag))
	    findcontext(CTXT_RESTART, c->cloenv, R_RestartToken);
	else if (c->callflag == CTXT_TOPLEVEL)
	    error(_("No function to return from, jumping to top level"));
    }
}

void NORET R_JumpToToplevel(Rboolean restart)
{
    RCNTXT *c;

    /* Find the target for the jump */
    for (c = R_GlobalContext; c != NULL; c = c->nextcontext) {
	if (restart && IS_RESTART_BIT_SET(c->callflag))
	    findcontext(CTXT_RESTART, c->cloenv, R_RestartToken);
	else if (c->callflag == CTXT_TOPLEVEL)
	    break;
    }
    if (c != R_ToplevelContext)
	warning(_("top level inconsistency?"));

    R_jumpctxt(R_ToplevelContext, CTXT_TOPLEVEL, NULL);
}
#endif

static void R_SetErrmessage(const char *s)
{
    strncpy(errbuf, s, sizeof(errbuf));
    errbuf[sizeof(errbuf) - 1] = 0;
}

static void R_PrintDeferredWarnings(void)
{
    if( R_ShowErrorMessages && R_CollectWarnings ) {
	REprintf(_("In addition: "));
	PrintWarnings();
    }
}

attribute_hidden
SEXP R_GetTraceback(int skip)
{
    int nback = 0, ns;
    RCNTXT *c;
    SEXP s, t;

    for (c = R_GlobalContext, ns = skip;
	 c != NULL && c->callflag != CTXT_TOPLEVEL;
	 c = c->nextcontext)
	if (c->callflag & (CTXT_FUNCTION | CTXT_BUILTIN) ) {
	    if (ns > 0)
		ns--;
	    else
		nback++;
	}

    PROTECT(s = allocList(nback));
    t = s;
    for (c = R_GlobalContext ;
	 c != NULL && c->callflag != CTXT_TOPLEVEL;
	 c = c->nextcontext)
	if (c->callflag & (CTXT_FUNCTION | CTXT_BUILTIN) ) {
	    if (skip > 0)
		skip--;
	    else {
		SETCAR(t, deparse1(c->call, 0, DEFAULTDEPARSE));
		if (c->srcref && !isNull(c->srcref))
		    setAttrib(CAR(t), R_SrcrefSymbol, duplicate(c->srcref));
		t = CDR(t);
	    }
	}
    UNPROTECT(1);
    return s;
}

SEXP attribute_hidden do_traceback(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    int skip;

    checkArity(op, args);
    skip = asInteger(CAR(args));

    if (skip == NA_INTEGER || skip < 0 )
	error(_("invalid '%s' value"), "skip");

    return R_GetTraceback(skip);
}

static char * R_ConciseTraceback(SEXP call, int skip)
{
    static char buf[560];
    RCNTXT *c;
    size_t nl;
    int ncalls = 0;
    Rboolean too_many = FALSE;
    const char *top = "" /* -Wall */;

    buf[0] = '\0';
    for (c = R_GlobalContext;
	 c != NULL && c->callflag != CTXT_TOPLEVEL;
	 c = c->nextcontext)
	if (c->callflag & (CTXT_FUNCTION | CTXT_BUILTIN) ) {
	    if (skip > 0)
		skip--;
	    else {
		SEXP fun = CAR(c->call);
		const char *this = (TYPEOF(fun) == SYMSXP) ?
		    CHAR(PRINTNAME(fun)) : "<Anonymous>";
		if(streql(this, "stop") ||
		   streql(this, "warning") ||
		   streql(this, "suppressWarnings") ||
		   streql(this, ".signalSimpleWarning")) {
		    buf[0] =  '\0'; ncalls = 0; too_many = FALSE;
		} else {
		    ncalls++;
		    if(too_many) {
			top = this;
		    } else if(strlen(buf) > R_NShowCalls) {
			memmove(buf+4, buf, strlen(buf)+1);
			memcpy(buf, "... ", 4);
			too_many = TRUE;
			top = this;
		    } else if(strlen(buf)) {
			nl = strlen(this);
			memmove(buf+nl+4, buf, strlen(buf)+1);
			memcpy(buf, this, strlen(this));
			memcpy(buf+nl, " -> ", 4);
		    } else
			memcpy(buf, this, strlen(this)+1);
		}
	    }
	}
    if(too_many && (nl = strlen(top)) < 50) {
	memmove(buf+nl+1, buf, strlen(buf)+1);
	memcpy(buf, top, strlen(top));
	memcpy(buf+nl, " ", 1);
    }
    /* don't add Calls if it adds no extra information */
    /* However: do we want to include the call in the list if it is a
       primitive? */
    if (ncalls == 1 && TYPEOF(call) == LANGSXP) {
	SEXP fun = CAR(call);
	const char *this = (TYPEOF(fun) == SYMSXP) ?
	    CHAR(PRINTNAME(fun)) : "<Anonymous>";
	if(streql(buf, this)) return "";
    }
    return buf;
}



static SEXP mkHandlerEntry(SEXP klass, SEXP parentenv, SEXP handler, SEXP rho,
			   SEXP result, int calling)
{
    SEXP entry = allocVector(VECSXP, 5);
    SET_VECTOR_ELT(entry, 0, klass);
    SET_VECTOR_ELT(entry, 1, parentenv);
    SET_VECTOR_ELT(entry, 2, handler);
    SET_VECTOR_ELT(entry, 3, rho);
    SET_VECTOR_ELT(entry, 4, result);
    SETLEVELS(entry, calling);
    return entry;
}

/**** rename these??*/
#define IS_CALLING_ENTRY(e) LEVELS(e)
#define ENTRY_CLASS(e) VECTOR_ELT(e, 0)
#define ENTRY_CALLING_ENVIR(e) VECTOR_ELT(e, 1)
#define ENTRY_HANDLER(e) VECTOR_ELT(e, 2)
#define ENTRY_TARGET_ENVIR(e) VECTOR_ELT(e, 3)
#define ENTRY_RETURN_RESULT(e) VECTOR_ELT(e, 4)

#define RESULT_SIZE 3

SEXP attribute_hidden do_addCondHands(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP classes, handlers, parentenv, target, oldstack, newstack, result;
    int calling, i, n;
    PROTECT_INDEX osi;

    checkArity(op, args);

    classes = CAR(args); args = CDR(args);
    handlers = CAR(args); args = CDR(args);
    parentenv = CAR(args); args = CDR(args);
    target = CAR(args); args = CDR(args);
    calling = asLogical(CAR(args));

    if (classes == R_NilValue || handlers == R_NilValue)
	return R_HandlerStack;

    if (TYPEOF(classes) != STRSXP || TYPEOF(handlers) != VECSXP ||
	LENGTH(classes) != LENGTH(handlers))
	error(_("bad handler data"));

    n = LENGTH(handlers);
    oldstack = R_HandlerStack;

    PROTECT(result = allocVector(VECSXP, RESULT_SIZE));
    PROTECT_WITH_INDEX(newstack = oldstack, &osi);

    for (i = n - 1; i >= 0; i--) {
	SEXP klass = STRING_ELT(classes, i);
	SEXP handler = VECTOR_ELT(handlers, i);
	SEXP entry = mkHandlerEntry(klass, parentenv, handler, target, result,
				    calling);
	REPROTECT(newstack = CONS(entry, newstack), osi);
    }

    R_HandlerStack = newstack;
    UNPROTECT(2);

    return oldstack;
}

SEXP attribute_hidden do_resetCondHands(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    R_HandlerStack = CAR(args);
    return R_NilValue;
}

static SEXP findSimpleErrorHandler(void)
{
    SEXP list;
    for (list = R_HandlerStack; list != R_NilValue; list = CDR(list)) {
	SEXP entry = CAR(list);
	if (! strcmp(CHAR(ENTRY_CLASS(entry)), "simpleError") ||
	    ! strcmp(CHAR(ENTRY_CLASS(entry)), "error") ||
	    ! strcmp(CHAR(ENTRY_CLASS(entry)), "condition"))
	    return list;
    }
    return R_NilValue;
}

static void vsignalWarning(SEXP call, const char *format, va_list ap)
{
    char buf[BUFSIZE];
    SEXP hooksym, hcall, qcall;

    hooksym = install(".signalSimpleWarning");
    if (SYMVALUE(hooksym) != R_UnboundValue &&
	SYMVALUE(R_QuoteSymbol) != R_UnboundValue) {
	PROTECT(qcall = LCONS(R_QuoteSymbol, LCONS(call, R_NilValue)));
	PROTECT(hcall = LCONS(qcall, R_NilValue));
	Rvsnprintf(buf, BUFSIZE - 1, format, ap);
	hcall = LCONS(mkString(buf), hcall);
	PROTECT(hcall = LCONS(hooksym, hcall));
	eval(hcall, R_GlobalEnv);
	UNPROTECT(3);
    }
    else vwarningcall_dflt(call, format, ap);
}

static void NORET gotoExitingHandler(SEXP cond, SEXP call, SEXP entry)
{
    SEXP rho = ENTRY_TARGET_ENVIR(entry);
    SEXP result = ENTRY_RETURN_RESULT(entry);
    SET_VECTOR_ELT(result, 0, cond);
    SET_VECTOR_ELT(result, 1, call);
    SET_VECTOR_ELT(result, 2, ENTRY_HANDLER(entry));
    findcontext(CTXT_FUNCTION, rho, result);
}

static void vsignalError(SEXP call, const char *format, va_list ap)
{
    char localbuf[BUFSIZE];
    SEXP list, oldstack;

    oldstack = R_HandlerStack;
    Rvsnprintf(localbuf, BUFSIZE - 1, format, ap);
    while ((list = findSimpleErrorHandler()) != R_NilValue) {
	char *buf = errbuf;
	SEXP entry = CAR(list);
	R_HandlerStack = CDR(list);
	strncpy(buf, localbuf, BUFSIZE - 1);
	/*	Rvsnprintf(buf, BUFSIZE - 1, format, ap);*/
	buf[BUFSIZE - 1] = 0;
	if (IS_CALLING_ENTRY(entry)) {
	    if (ENTRY_HANDLER(entry) == R_RestartToken)
		return; /* go to default error handling; do not reset stack */
	    else {
		/* if we are in the process of handling a C stack
		   overflow, treat all calling handlers ar failed */
		if (R_OldCStackLimit)
		    break;
		SEXP hooksym, hcall, qcall;
		/* protect oldstack here, not outside loop, so handler
		   stack gets unwound in case error is protect stack
		   overflow */
		PROTECT(oldstack);
		hooksym = install(".handleSimpleError");
		PROTECT(qcall = LCONS(R_QuoteSymbol,
				      LCONS(call, R_NilValue)));
		PROTECT(hcall = LCONS(qcall, R_NilValue));
		hcall = LCONS(mkString(buf), hcall);
		hcall = LCONS(ENTRY_HANDLER(entry), hcall);
		PROTECT(hcall = LCONS(hooksym, hcall));
		eval(hcall, R_GlobalEnv);
		UNPROTECT(4);
	    }
	}
	else gotoExitingHandler(R_NilValue, call, entry);
    }
    R_HandlerStack = oldstack;
}

static SEXP findConditionHandler(SEXP cond)
{
    int i;
    SEXP list;
    SEXP classes = getAttrib(cond, R_ClassSymbol);

    if (TYPEOF(classes) != STRSXP)
	return R_NilValue;

    /**** need some changes here to allow conditions to be S4 classes */
    for (list = R_HandlerStack; list != R_NilValue; list = CDR(list)) {
	SEXP entry = CAR(list);
	for (i = 0; i < LENGTH(classes); i++)
	    if (! strcmp(CHAR(ENTRY_CLASS(entry)),
			 CHAR(STRING_ELT(classes, i))))
		return list;
    }
    return R_NilValue;
}

SEXP attribute_hidden do_signalCondition(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP list, cond, msg, ecall, oldstack;

    checkArity(op, args);

    cond = CAR(args);
    msg = CADR(args);
    ecall = CADDR(args);

    PROTECT(oldstack = R_HandlerStack);
    while ((list = findConditionHandler(cond)) != R_NilValue) {
	SEXP entry = CAR(list);
	R_HandlerStack = CDR(list);
	if (IS_CALLING_ENTRY(entry)) {
	    SEXP h = ENTRY_HANDLER(entry);
	    if (h == R_RestartToken) {
		const char *msgstr = NULL;
		if (TYPEOF(msg) == STRSXP && LENGTH(msg) > 0)
		    msgstr = translateChar(STRING_ELT(msg, 0));
		else error(_("error message not a string"));
		errorcall_dflt(ecall, "%s", msgstr);
	    }
	    else {
		SEXP hcall = LCONS(h, LCONS(cond, R_NilValue));
		PROTECT(hcall);
		eval(hcall, R_GlobalEnv);
		UNPROTECT(1);
	    }
	}
	else gotoExitingHandler(cond, ecall, entry);
    }
    R_HandlerStack = oldstack;
    UNPROTECT(1);
    return R_NilValue;
}

static SEXP findInterruptHandler(void)
{
    SEXP list;
    for (list = R_HandlerStack; list != R_NilValue; list = CDR(list)) {
	SEXP entry = CAR(list);
	if (! strcmp(CHAR(ENTRY_CLASS(entry)), "interrupt") ||
	    ! strcmp(CHAR(ENTRY_CLASS(entry)), "condition"))
	    return list;
    }
    return R_NilValue;
}

static SEXP getInterruptCondition(void)
{
    /**** FIXME: should probably pre-allocate this */
    SEXP cond, klass;
    PROTECT(cond = allocVector(VECSXP, 0));
    PROTECT(klass = allocVector(STRSXP, 2));
    SET_STRING_ELT(klass, 0, mkChar("interrupt"));
    SET_STRING_ELT(klass, 1, mkChar("condition"));
    classgets(cond, klass);
    UNPROTECT(2);
    return cond;
}

static void signalInterrupt(void)
{
    SEXP list, cond, oldstack;

    PROTECT(oldstack = R_HandlerStack);
    while ((list = findInterruptHandler()) != R_NilValue) {
	SEXP entry = CAR(list);
	R_HandlerStack = CDR(list);
	PROTECT(cond = getInterruptCondition());
	if (IS_CALLING_ENTRY(entry)) {
	    SEXP h = ENTRY_HANDLER(entry);
	    SEXP hcall = LCONS(h, LCONS(cond, R_NilValue));
	    PROTECT(hcall);
	    eval(hcall, R_GlobalEnv);
	    UNPROTECT(1);
	}
	else gotoExitingHandler(cond, R_NilValue, entry);
	UNPROTECT(1);
    }
    R_HandlerStack = oldstack;
    UNPROTECT(1);
}

void attribute_hidden
R_InsertRestartHandlers(RCNTXT *cptr, Rboolean browser)
{
    SEXP klass, rho, entry, name;

    if ((cptr->handlerstack != R_HandlerStack ||
	 cptr->restartstack != R_RestartStack)) {
	if (IS_RESTART_BIT_SET(cptr->callflag))
	    return;
	else
	    error(_("handler or restart stack mismatch in old restart"));
    }

    /**** need more here to keep recursive errors in browser? */
    rho = cptr->cloenv;
    PROTECT(klass = mkChar("error"));
    entry = mkHandlerEntry(klass, rho, R_RestartToken, rho, R_NilValue, TRUE);
    R_HandlerStack = CONS(entry, R_HandlerStack);
    UNPROTECT(1);
    PROTECT(name = mkString(browser ? "browser" : "tryRestart"));
    PROTECT(entry = allocVector(VECSXP, 2));
    SET_VECTOR_ELT(entry, 0, name);
    SET_VECTOR_ELT(entry, 1, R_MakeExternalPtr(cptr, R_NilValue, R_NilValue));
    setAttrib(entry, R_ClassSymbol, mkString("restart"));
    R_RestartStack = CONS(entry, R_RestartStack);
    UNPROTECT(2);
}

SEXP attribute_hidden do_dfltWarn(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    const char *msg;
    SEXP ecall;

    checkArity(op, args);

    if (TYPEOF(CAR(args)) != STRSXP || LENGTH(CAR(args)) != 1)
	error(_("bad error message"));
    msg = translateChar(STRING_ELT(CAR(args), 0));
    ecall = CADR(args);

    warningcall_dflt(ecall, "%s", msg);
    return R_NilValue;
}

SEXP attribute_hidden NORET do_dfltStop(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    const char *msg;
    SEXP ecall;

    checkArity(op, args);

    if (TYPEOF(CAR(args)) != STRSXP || LENGTH(CAR(args)) != 1)
	error(_("bad error message"));
    msg = translateChar(STRING_ELT(CAR(args), 0));
    ecall = CADR(args);

    errorcall_dflt(ecall, "%s", msg);
}


/*
 * Restart Handling
 */

SEXP attribute_hidden do_getRestart(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    int i;
    SEXP list;
    checkArity(op, args);
    i = asInteger(CAR(args));
    for (list = R_RestartStack;
	 list != R_NilValue && i > 1;
	 list = CDR(list), i--);
    if (list != R_NilValue)
	return CAR(list);
    else if (i == 1) {
	/**** need to pre-allocate */
	SEXP name, entry;
	PROTECT(name = mkString("abort"));
	PROTECT(entry = allocVector(VECSXP, 2));
	SET_VECTOR_ELT(entry, 0, name);
	SET_VECTOR_ELT(entry, 1, R_NilValue);
	setAttrib(entry, R_ClassSymbol, mkString("restart"));
	UNPROTECT(2);
	return entry;
    }
    else return R_NilValue;
}

/* very minimal error checking --just enough to avoid a segfault */
#define CHECK_RESTART(r) do { \
    SEXP __r__ = (r); \
    if (TYPEOF(__r__) != VECSXP || LENGTH(__r__) < 2) \
	error(_("bad restart")); \
} while (0)

SEXP attribute_hidden do_addRestart(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    CHECK_RESTART(CAR(args));
    R_RestartStack = CONS(CAR(args), R_RestartStack);
    return R_NilValue;
}

#define RESTART_EXIT(r) VECTOR_ELT(r, 1)

static void NORET invokeRestart(SEXP r, SEXP arglist)
{
    SEXP exit = RESTART_EXIT(r);

    if (exit == R_NilValue) {
	R_RestartStack = R_NilValue;
	jump_to_toplevel();
    }
    else {
	for (; R_RestartStack != R_NilValue;
	     R_RestartStack = CDR(R_RestartStack))
	    if (exit == RESTART_EXIT(CAR(R_RestartStack))) {
		R_RestartStack = CDR(R_RestartStack);
		if (TYPEOF(exit) == EXTPTRSXP) {
		    RCNTXT *c = (RCNTXT *) R_ExternalPtrAddr(exit);
		    R_JumpToContext(c, CTXT_RESTART, R_RestartToken);
		}
		else findcontext(CTXT_FUNCTION, exit, arglist);
	    }
	error(_("restart not on stack"));
    }
}

SEXP attribute_hidden NORET do_invokeRestart(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    CHECK_RESTART(CAR(args));
    invokeRestart(CAR(args), CADR(args));
}

SEXP attribute_hidden do_addTryHandlers(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    if (R_GlobalContext == R_ToplevelContext ||
	! (R_GlobalContext->callflag & CTXT_FUNCTION))
	errorcall(call, _("not in a try context"));
    SET_RESTART_BIT_ON(R_GlobalContext->callflag);
    R_InsertRestartHandlers(R_GlobalContext, FALSE);
    return R_NilValue;
}

SEXP attribute_hidden do_seterrmessage(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP msg;

    checkArity(op, args);
    msg = CAR(args);
    if(!isString(msg) || LENGTH(msg) != 1)
	error(_("error message must be a character string"));
    R_SetErrmessage(CHAR(STRING_ELT(msg, 0)));
    return R_NilValue;
}

SEXP attribute_hidden
do_printDeferredWarnings(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    R_PrintDeferredWarnings();
    return R_NilValue;
}

SEXP attribute_hidden
do_interruptsSuspended(SEXP call, SEXP op, SEXP args, SEXP env)
{
    int orig_value = R_interrupts_suspended;
    if (args != R_NilValue)
	R_interrupts_suspended = asLogical(CAR(args));
    return ScalarLogical(orig_value);
}

/* These functions are to be used in error messages, and available for others to use in the API
   GetCurrentSrcref returns the first non-NULL srcref after skipping skip of them.  If it
   doesn't find one it returns NULL. */

SEXP
R_GetCurrentSrcref(int skip)
{
    RCNTXT *c = R_GlobalContext;
    SEXP srcref = R_Srcref;
    if (skip < 0) { /* to count up from the bottom, we need to count them all first */
	while (c) {
	    if (srcref && srcref != R_NilValue)
		skip++;
	    srcref = c->srcref;
	    c = c->nextcontext;
	};
	if (skip < 0) return R_NilValue; /* not enough there */
	c = R_GlobalContext;
	srcref = R_Srcref;
    }
    while (c && (skip || !srcref || srcref == R_NilValue)) {
	if (srcref && srcref != R_NilValue)
	    skip--;
	srcref = c->srcref;
	c = c->nextcontext;
    }
    if (skip || !srcref)
	srcref = R_NilValue;
    return srcref;
}

/* Return the filename corresponding to a srcref, or "" if none is found */

SEXP
R_GetSrcFilename(SEXP srcref)
{
    SEXP srcfile = getAttrib(srcref, R_SrcfileSymbol);
    if (TYPEOF(srcfile) != ENVSXP)
	return ScalarString(mkChar(""));
    srcfile = findVar(install("filename"), srcfile);
    if (TYPEOF(srcfile) != STRSXP)
	return ScalarString(mkChar(""));
    return srcfile;
}
