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errors.c

/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1997--2005  The R Development 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, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/* <UTF8> char here is either ASCII or handled as a whole */

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

#ifdef HAVE_AQUA
extern void R_ProcessEvents(void);
#endif

#include <Defn.h>
/* -> Errormsg.h */
#include <Startup.h> /* rather cleanup ..*/
#include <Rconnections.h>
#include <R_ext/GraphicsDevice.h>
#include <R_ext/GraphicsEngine.h> /* for GEonExit */
#include <Rmath.h> /* for imax2 */

#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#endif
#if !HAVE_DECL_ALLOCA
extern char *alloca(size_t);
#endif

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

/* limit on call length at which errorcall/warningcall is split over
   two lines */
#define LONGCALL 30

/*
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 void try_jump_to_restart(void);
static void jump_to_top_ex(Rboolean, Rboolean, Rboolean, Rboolean, Rboolean);
static void signalInterrupt(void);

/* Interface / Calling Hierarchy :

  R__stop()   -> do_error ->   errorcall --> 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 R_CheckUserInterrupt(void)
{
    /* 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 */
#if  ( defined(HAVE_AQUA) || defined(Win32) )
    R_ProcessEvents();
#else
    if (R_interrupts_pending)
      onintr();
#endif /* Win32 */
}

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().
*/

void onsigusr1()
{
    if (R_interrupts_suspended) {
      /**** ought to save signal and handle after suspend */
      REprintf(_("interrupts suspended; signal ignored"));
      return;
    }

    inError = 1;

    if( R_CollectWarnings )
      PrintWarnings();

    R_ResetConsole();
    R_FlushConsole();
    R_ClearerrConsole();
    R_ParseError = 0;

    /* Bail out if there is a browser/try on the stack--do we really
       want this? */
    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 */
}


void onsigusr2()
{
    inError = 1;

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

    if( R_CollectWarnings )
      PrintWarnings();

    R_ResetConsole();
    R_FlushConsole();
    R_ClearerrConsole();
    R_ParseError = 0;
    R_CleanUp(SA_SAVE, 0, 0);
}


static void setupwarnings(void)
{
    R_Warnings = allocVector(VECSXP, 50);
    setAttrib(R_Warnings, R_NamesSymbol, allocVector(STRSXP, 50));
}

/* Rvsnprintf: like vsnprintf, but guaranteed to null-terminate. */
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;
}

#define BUFSIZE 8192
void warning(const char *format, ...)
{
    char buf[BUFSIZE], *p;

    va_list(ap);
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
    va_end(ap);
    p = buf + strlen(buf) - 1;
    if(strlen(buf) > 0 && *p == '\n') *p = '\0';
    warningcall(R_NilValue, buf);
}

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

#ifdef NEW_CONDITION_HANDLING
/* 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 invokeRestart(SEXP, SEXP);
#endif

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

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

    if (inWarning)
      return;

    s = GetOption(install("warning.expression"), R_NilValue);
    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(GetOption(install("warn"), R_NilValue));

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

    if(w < 0 || inWarning || inError)  {/* ignore if w<0 or already in here*/
      return;
    }
    if( w == 0 && immediateWarning ) w = 1;

    /* set up a context which will restore inWarning if there is an exit */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_NilValue, R_NilValue,
             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);
      inWarning = 0; /* PR#1570 */
      errorcall(call, _("(converted from warning) %s"), buf);
    }
    else if(w == 1) {   /* print as they happen */
      if( call != R_NilValue ) {
          dcall = CHAR(STRING_ELT(deparse1(call, 0, SIMPLEDEPARSE), 0));
          REprintf(_("Warning in %s : "), dcall);
          if (strlen(dcall) > LONGCALL) REprintf("\n   ");
      }
      else
          REprintf(_("Warning: "));
      Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
      REprintf("%s\n", buf);
    }
    else if(w == 0) {   /* collect them */
      if(!R_CollectWarnings)
          setupwarnings();
      if( R_CollectWarnings > 49 )
          return;
      SET_VECTOR_ELT(R_Warnings, R_CollectWarnings, call);
      Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
      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);
#ifdef NEW_CONDITION_HANDLING
    va_start(ap, format);
    vsignalWarning(call, format, ap);
    va_end(ap);
#else
    if (R_WarningHook != NULL) {
      char buf[BUFSIZE];
      va_start(ap, format);
      Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
      va_end(ap);
      R_WarningHook(call, buf);
      return;
    }

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

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

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_NilValue, R_NilValue,
             R_NilValue, R_NilValue);
    cntxt.cend = &cleanup_PrintWarnings;

    inPrintWarnings = 1;
    header = ngettext("Warning message:\n", "Warning messages:\n", 
                  R_CollectWarnings);
    if( R_CollectWarnings == 1 ) {
      REprintf(header);
      names = CAR(ATTRIB(R_Warnings));
      if( VECTOR_ELT(R_Warnings, 0) == R_NilValue )
         REprintf("%s \n", CHAR(STRING_ELT(names, 0)));
      else
         REprintf("%s in: %s \n", CHAR(STRING_ELT(names, 0)),
            CHAR(STRING_ELT(deparse1(VECTOR_ELT(R_Warnings, 0), 0, SIMPLEDEPARSE), 0)));
    }
    else if( R_CollectWarnings <= 10 ) {
      REprintf(header);
      names = CAR(ATTRIB(R_Warnings));
      for(i=0; i<R_CollectWarnings; i++) {
          if( STRING_ELT(R_Warnings, i) == R_NilValue )
             REprintf("%d: %s \n",i+1, CHAR(STRING_ELT(names, i)));
          else
             REprintf("%d: %s in: %s \n", i+1, CHAR(STRING_ELT(names, i)),
               CHAR(STRING_ELT(deparse1(VECTOR_ELT(R_Warnings,i), 0, SIMPLEDEPARSE), 0)));
      }
    }
    else {
      if (R_CollectWarnings < 50)
          REprintf(_("There were %d warnings (use warnings() to see them)\n"),
                 R_CollectWarnings);
      else
          REprintf(_("There were 50 or more warnings (use warnings() to see the first 50)\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_VECTOR_ELT(t, i, VECTOR_ELT(names, i));
    }
    setAttrib(s, R_NamesSymbol, t);
    defineVar(install("last.warning"), s, R_GlobalEnv);
    UNPROTECT(2);

    endcontext(&cntxt);

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

static char errbuf[BUFSIZE];

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

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

static void verrorcall_dflt(SEXP call, const char *format, va_list ap)
{
    RCNTXT cntxt;
    char *p, *dcall;
    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"));
      }
      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_NilValue, R_NilValue,
             R_NilValue, R_NilValue);
    cntxt.cend = &restore_inError;
    cntxt.cenddata = &oldInError;
    oldInError = inError;
    inError = 1;

    if(call != R_NilValue) {
      char *head = _("Error in ");
      char *mid = " : ";
      char *tail = "\n\t";/* <- TAB */
      int len = strlen(head) + strlen(mid) + strlen(tail);

      dcall = CHAR(STRING_ELT(deparse1(call, 0, SIMPLEDEPARSE), 0));
      if (strlen(dcall) + len < BUFSIZE) {
          sprintf(errbuf, "%s%s%s", head, dcall, mid);
          if (strlen(dcall) > LONGCALL) strcat(errbuf, tail);
      }
      else
          sprintf(errbuf, _("Error: "));
    }
    else
      sprintf(errbuf, _("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_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 errorcall_dflt(SEXP call, const char *format,...)
{
    va_list(ap);

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

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

#ifdef NEW_CONDITION_HANDLING
    va_start(ap, format);
    vsignalError(call, format, ap);
    va_end(ap);
#endif

    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 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];

    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... */
    errorcall(R_GlobalContext ?
            R_GlobalContext->call : R_NilValue, "%s", buf);
}

static void try_jump_to_restart(void)
{
#ifdef NEW_CONDITION_HANDLING
    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) {
            char *cname = CHAR(STRING_ELT(name, 0));
            if (! strcmp(cname, "browser") ||
                ! strcmp(cname, "tryRestart") ||
                ! strcmp(cname, "abort")) /**** move abort eventually? */
                invokeRestart(restart, R_NilValue);
          }
      }
    }
#else
    RCNTXT *c;

    for (c = R_GlobalContext; c; c = c->nextcontext) {
      if (IS_RESTART_BIT_SET(c->callflag)) {
          inError=0;
          findcontext(CTXT_RESTART, c->cloenv, R_RestartToken);
      }
      if (c->callflag == CTXT_TOPLEVEL)
          break;
    }
#endif
}

/* 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_NilValue, R_NilValue,
             R_NilValue, R_NilValue);
    cntxt.cend = &restore_inError;
    cntxt.cenddata = &oldInError;

    oldInError = inError;

    haveHandler = FALSE;

    if (tryUserHandler && inError < 3) {
      if (! inError)
          inError = 1;

      /*now see if options("error") is set */
      s = GetOption(install("error"), R_NilValue);
      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;
    }

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

    /* WARNING: If oldInError > 0 ABSOLUTELY NO ALLOCATION can be
       triggered after this point except whatever happens in writing
       the traceback and R_run_onexits.  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 inconsistenty between inError and oldInError
         (which should not happen) */
      if (traceback && inError < 2 && inError == oldInError) {
          inError = 2;
          PROTECT(s = R_GetTraceback(0));
          setVar(install(".Traceback"), s, R_GlobalEnv);
          UNPROTECT(1);
          inError = oldInError;
      }
    }

    /* Run onexit/cend code for all contexts down to but not including
       the jump target.  This may cause recursive calls to
       jump_to_top_ex, but the possible number of such recursive
       calls is limited since each exit function is removed before it
       is executed.  In addition, all but the first should have
       inError > 0.  This is not a great design because we could run
       out of other resources that are on the stack (like C stack for
       example).  The right thing to do is arrange to execute exit
       code *after* the LONGJMP, but that requires a more extensive
       redesign of the non-local transfer of control mechanism.
       LT. */
    R_run_onexits(R_ToplevelContext);

    if ( !R_Interactive && !haveHandler ) {
      REprintf(_("Execution halted\n"));
      R_CleanUp(SA_NOSAVE, 1, 0); /* quit, no save, no .Last, status=1 */
    }

    R_GlobalContext = R_ToplevelContext;
    R_restore_globals(R_GlobalContext);
    LONGJMP(R_ToplevelContext->cjmpbuf, 0);
    /* not reached */
    endcontext(&cntxt);
    inError = oldInError;
}

void 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 do_gettext(SEXP call, SEXP op, SEXP args, SEXP rho)
{
#ifdef ENABLE_NLS
    char *domain = "", *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 'string' value"));

    if(isNull(CAR(args))) {
      RCNTXT *cptr;
      SEXP rho = R_NilValue;
      for (cptr = R_GlobalContext->nextcontext;
           cptr != NULL && cptr->callflag != CTXT_TOPLEVEL;
           cptr = cptr->nextcontext)
          if (cptr->callflag & CTXT_FUNCTION) {
            rho = cptr->cloenv;
            break;
          }
      while(rho != R_NilValue) {
          if (rho == R_GlobalEnv) break;
          else if (R_IsNamespaceEnv(rho)) {
            domain = CHAR(STRING_ELT(R_NamespaceEnvSpec(rho), 0));
            break;
          }
          rho = CDR(rho);
      }
      if(strlen(domain)) {
          buf = alloca(strlen(domain)+3);
          sprintf(buf, "R-%s", domain);
          domain = buf;
      }
    } else if(isString(CAR(args)))
      domain = CHAR(STRING_ELT(CAR(args),0));
    else errorcall(call, _("invalid 'domain' value"));

    if(strlen(domain)) {
      PROTECT(ans = allocVector(STRSXP, n));
      for(i = 0; i < n; i++) {
          int ihead = 0, itail = 0;
          char *this = CHAR(STRING_ELT(string, i)), 
            *tmp, *head = NULL, *tail = NULL, *p, *tr;
          tmp = 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) {
            head = 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) {
            tail = 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);
            tmp = alloca(strlen(tr) + ihead + itail + 1);
            tmp[0] ='\0';
            if(ihead > 0) strcat(tmp, head);
            strcat(tmp, tr);
            if(itail > 0) strcat(tmp, tail);
          } else tmp = this;
          SET_STRING_ELT(ans, i, mkChar(tmp));
      }
      UNPROTECT(1);
      return ans;
    } else return CADR(args);
#else
    return CADR(args);
#endif
}

/* ngettext(n, msg1, msg2, domain) */
SEXP do_ngettext(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    char *domain = "", *buf;
    SEXP ans, sdom = CADDDR(args), msg1 = CADR(args), msg2 = CADDR(args);
    int n = asInteger(CAR(args));
    
    checkArity(op, args);
    if(n == NA_INTEGER || n < 0) error(_("invalid 'n'"));
    if(!isString(msg1) || LENGTH(msg1) != 1)
      error(_("'msg1' must be a character string"));
    if(!isString(msg2) || LENGTH(msg2) != 1)
      error(_("'msg2' must be a character string"));

#ifdef ENABLE_NLS
    if(isNull(sdom)) {
      RCNTXT *cptr;
      SEXP rho = R_NilValue;
      for (cptr = R_GlobalContext->nextcontext;
           cptr != NULL && cptr->callflag != CTXT_TOPLEVEL;
           cptr = cptr->nextcontext)
          if (cptr->callflag & CTXT_FUNCTION) {
            rho = cptr->cloenv;
            break;
          }
      while(rho != R_NilValue) {
          if (rho == R_GlobalEnv) break;
          else if (R_IsNamespaceEnv(rho)) {
            domain = CHAR(STRING_ELT(R_NamespaceEnvSpec(rho), 0));
            break;
          }
          rho = CDR(rho);
      }
      if(strlen(domain)) {
          buf = alloca(strlen(domain)+3);
          sprintf(buf, "R-%s", domain);
          domain = buf;
      }
    } else if(isString(sdom))
      domain = CHAR(STRING_ELT(sdom,0));
    else errorcall(call, _("invalid 'domain' value"));

    if(strlen(domain)) {
      char *fmt = dngettext(domain,
                        CHAR(STRING_ELT(msg1, 0)),
                        CHAR(STRING_ELT(msg2, 0)),
                        n);
      PROTECT(ans = allocVector(STRSXP, 1));
      SET_STRING_ELT(ans, 0, mkChar(fmt));
      UNPROTECT(1);
      return ans;
    } else
#endif
      return n == 1 ? msg1 : msg2;
}


/* bindtextdomain(domain, dirname) */
SEXP 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 'domain' value"));
    if(isNull(CADR(args))) {
      res = bindtextdomain(CHAR(STRING_ELT(CAR(args),0)), NULL);
    } else {
      if(!isString(CADR(args)) || LENGTH(CADR(args)) != 1) 
          errorcall(call, _("invalid 'dirname' value"));
      res = bindtextdomain(CHAR(STRING_ELT(CAR(args),0)),
                       CHAR(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 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;

    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", CHAR(STRING_ELT(CAR(args), 0)));
    }
    else
      errorcall(c_call, "");
    /* never called: */return c_call;
}

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

    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 (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", CHAR(STRING_ELT(CAR(args), 0)));
    }
    else
      warningcall(c_call, "");
    immediateWarning = 0; /* reset to internal calls */

    /* need to set R_Visible since it may have been changed by a callback */
    R_Visible = 0;
    return CAR(args);
}

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


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

/* ERROR_.. codes in Errormsg.h */
static struct {
    const R_WARNING 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!)")      },
};


void 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);
}

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);
}


/* Temporary hooks to allow experimenting with alternate error and
   warning mechanisms.  They are not in the header files for now, but
   the following snippet can serve as a header file: */

void R_ReturnOrRestart(SEXP val, SEXP env, Rboolean restart);
void R_PrintDeferredWarnings(void);
void R_SetErrmessage(char *s);
void R_SetErrorHook(void (*hook)(SEXP, char *));
void R_SetWarningHook(void (*hook)(SEXP, char *));
void R_JumpToToplevel(Rboolean restart);


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 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?"));

    /* Run onexit/cend code for everything above the target. */
    R_run_onexits(c);

    R_ToplevelContext = R_GlobalContext = c;
    R_restore_globals(R_GlobalContext);
    LONGJMP(c->cjmpbuf, CTXT_TOPLEVEL);
}

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

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

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 ) {
          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 ) {
          if (skip > 0)
            skip--;
          else {
            SETCAR(t, deparse1(c->call, 0, SIMPLEDEPARSE));
            t = CDR(t);
          }
      }
    UNPROTECT(1);
    return s;
}

#ifdef NEW_CONDITION_HANDLING
static SEXP mkHandlerEntry(SEXP class, SEXP parentenv, SEXP handler, SEXP rho,
                     SEXP result, int calling)
{
    SEXP entry = allocVector(VECSXP, 5);
    SET_VECTOR_ELT(entry, 0, class);
    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 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 class = STRING_ELT(classes, i);
      SEXP handler = VECTOR_ELT(handlers, i);
      SEXP entry = mkHandlerEntry(class, parentenv, handler, target, result,
                            calling);
      REPROTECT(newstack = CONS(entry, newstack), osi);
    }

    R_HandlerStack = newstack;
    UNPROTECT(2);

    return oldstack;
}

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

static SEXP findSimpleErrorHandler()
{
    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, quotesym, hcall, qcall;

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

static void 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)
{
    SEXP list, oldstack;

    oldstack = R_HandlerStack;
    while ((list = findSimpleErrorHandler()) != R_NilValue) {
      char *buf = errbuf;
      SEXP entry = CAR(list);
      R_HandlerStack = CDR(list);
      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 {
            SEXP hooksym, quotesym, 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");
            quotesym = install("quote");
            PROTECT(qcall = LCONS(quotesym, LCONS(call, R_NilValue)));
            PROTECT(hcall = LCONS(qcall, R_NilValue));
            hcall = LCONS(ScalarString(mkChar(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 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) {
            char *msgstr = NULL;
            if (TYPEOF(msg) == STRSXP && LENGTH(msg) > 0)
                msgstr = CHAR(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()
{
    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()
{
    /**** FIXME: should probably pre-allocate this */
    SEXP cond, class;
    PROTECT(cond = allocVector(VECSXP, 0));
    PROTECT(class = allocVector(STRSXP, 2));
    SET_STRING_ELT(class, 0, mkChar("interrupt"));
    SET_STRING_ELT(class, 1, mkChar("condition"));
    R_set_class(cond, class, R_NilValue);
    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 R_InsertRestartHandlers(RCNTXT *cptr, Rboolean browser)
{
    SEXP class, rho, entry, name;

    if ((cptr->handlerstack != R_HandlerStack ||
       cptr->handlerstack != R_HandlerStack)) {
      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(class = mkChar("error"));
    entry = mkHandlerEntry(class, rho, R_RestartToken, rho, R_NilValue, TRUE);
    R_HandlerStack = CONS(entry, R_HandlerStack);
    UNPROTECT(1);
    PROTECT(name = ScalarString(mkChar(browser ? "browser" : "tryRestart")));
    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, ScalarString(mkChar("restart")));
    R_RestartStack = CONS(entry, R_RestartStack);
    UNPROTECT(1);
}

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

    checkArity(op, args);

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

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

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

    checkArity(op, args);

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

    errorcall_dflt(ecall, "%s", msg);
    return R_NilValue; /* not reached */
}


/*
 * Restart Handling
 */

SEXP 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 = ScalarString(mkChar("abort")));
      entry = allocVector(VECSXP, 2);
      SET_VECTOR_ELT(entry, 0, name);
      SET_VECTOR_ELT(entry, 1, R_NilValue);
      setAttrib(entry, R_ClassSymbol, ScalarString(mkChar("restart")));
      UNPROTECT(1);
      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 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 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 = R_ExternalPtrAddr(exit);
                R_JumpToContext(c, CTXT_RESTART, R_RestartToken);
            }
            else findcontext(CTXT_FUNCTION, exit, arglist);
          }
      error(_("restart not on stack"));
    }
}

SEXP do_invokeRestart(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    CHECK_RESTART(CAR(args));
    invokeRestart(CAR(args), CADR(args));
    return R_NilValue; /* not reached */
}
#endif

SEXP 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);
#ifdef NEW_CONDITION_HANDLING
    R_InsertRestartHandlers(R_GlobalContext, FALSE);
#endif
    return R_NilValue;
}

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