The R Project SVN R

/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1997--2002  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
 */

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

#include <Defn.h>
/* -> Errormsg.h */
#include <Startup.h> /* rather cleanup ..*/
#include <Rconnections.h>

#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 void try_jump_to_restart(void);
static void jump_to_top_ex(Rboolean, Rboolean, Rboolean, Rboolean, Rboolean);

/* 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 */
#ifdef Win32
    R_ProcessEvents();
#else
    if (R_interrupts_pending) {
    R_interrupts_pending = 0;
    onintr();
    }
#endif /* Win32 */
}

void onintr()
{
    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;

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

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

    if (inWarning)
    return;
    
    if (R_WarningHook != NULL) {
    va_list(ap);
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
    va_end(ap);
    R_WarningHook(call, buf);
    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;
    }

    /* 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 */
    va_list(ap);
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
    va_end(ap);
    inWarning = 0; /* PR#1570 */
    errorcall(call, "(converted from warning) %s", buf);
    }
    else if(w == 1) {   /* print as they happen */
    va_list(ap);
    if( call != R_NilValue ) {
        dcall = CHAR(STRING_ELT(deparse1(call, 0), 0));
        REprintf("Warning in %s : ", dcall);
        if (strlen(dcall) > LONGCALL) REprintf("\n   ");
    }
    else
        REprintf("Warning: ");
    va_start(ap, format);
    Rvsnprintf(buf, min(BUFSIZE, R_WarnLength), format, ap);
    va_end(ap);
    REprintf("%s\n", buf);
    }
    else if(w == 0) {   /* collect them */
    va_list(ap);
    va_start(ap, format);
    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);
    va_end(ap);
    names = CAR(ATTRIB(R_Warnings));
    SET_STRING_ELT(names, R_CollectWarnings++, mkChar(buf));
    }
    /* else:  w <= -1 */
    endcontext(&cntxt);
    inWarning = 0;
}

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;
    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;
    if( R_CollectWarnings == 1 ) {
    REprintf("Warning message: \n");
    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), 0)));
    }
    else if( R_CollectWarnings <= 10 ) {
    REprintf("Warning messages: \n");
    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), 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;
}

void errorcall(SEXP call, const char *format,...)
{
    RCNTXT cntxt;
    char *p, *dcall;
    int oldInError;

    va_list(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);
    }

    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 */
        va_start(ap, format);
        Rvsnprintf(errbuf, sizeof(errbuf), format, ap);
        va_end(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), 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);
    va_start(ap, format);
    Rvsnprintf(p, min(BUFSIZE, R_WarnLength) - strlen(errbuf), format, ap);
    va_end(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;
}

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)
{
    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;
    }
}

/* 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;
    }

    /* WARNING: If oldInError > 0 ABSOLUTELY NO ALLOCATION can be
       triggered after this point except whatever happens in
       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 */

    /* 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 */
    }

    if (traceback) {
    PROTECT(s = R_GetTraceback(0));
    setVar(install(".Traceback"), s, R_GlobalEnv);
    UNPROTECT(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);
}

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

    if(asLogical(CAR(args))) {/* find context -> "Error in ..:" */
    cptr = R_GlobalContext->nextcontext;
    while ( !(cptr->callflag & CTXT_FUNCTION) && cptr->nextcontext != NULL)
        cptr = cptr->nextcontext;
    c_call = cptr->call;
    }
    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)
{
    RCNTXT *cptr;
    SEXP c_call;

    if(asLogical(CAR(args))) {/* find context -> "... in: ..:" */
    cptr = R_GlobalContext->nextcontext;
    while ( !(cptr->callflag & CTXT_FUNCTION) && 
        cptr->nextcontext != NULL)
        cptr = cptr->nextcontext;
    c_call = cptr->call;
    } else
    c_call = R_NilValue;

    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, "");
    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,        "invalid number of arguments"       },
    { ERROR_ARGTYPE,        "invalid argument type"         },

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

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

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

    { WARNING_UNKNOWN,      "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();
    }
}    

/* doesn't stop at TOPLEVEL--should once browser is changed to use RESTART */
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));
        t = CDR(t);
        }
    }
    UNPROTECT(1);
    return s;
}