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Up to [gforth] / gforth / engine

there is now a debugging version of the engine that maintains ip and
rp in global variables (to allow backtrace on signals). The debugging
engine is called gforth and the original engine is called gforth-fast.

/* command line interpretation, image loading etc. for Gforth


  Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.

  This file is part of Gforth.

  Gforth 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "config.h"
#include <errno.h>
#include <ctype.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <stdlib.h>
#ifndef STANDALONE
#if HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif
#endif
#include "forth.h"
#include "io.h"
#include "getopt.h"
#ifdef STANDALONE
#include <systypes.h>
#endif

#define PRIM_VERSION 1
/* increment this whenever the primitives change in an incompatible way */

#ifndef DEFAULTPATH
#  define DEFAULTPATH "~+"
#endif

#ifdef MSDOS
jmp_buf throw_jmp_buf;
#endif

#if defined(DIRECT_THREADED) 
#  define CA(n)	(symbols[(n)])
#else
#  define CA(n)	((Cell)(symbols+(n)))
#endif

#define maxaligned(n)	(typeof(n))((((Cell)n)+sizeof(Float)-1)&-sizeof(Float))

static UCell dictsize=0;
static UCell dsize=0;
static UCell rsize=0;
static UCell fsize=0;
static UCell lsize=0;
int offset_image=0;
int die_on_signal=0;
#ifndef INCLUDE_IMAGE
static int clear_dictionary=0;
static size_t pagesize=0;
#endif
static int debug=0;
char *progname;

/* image file format:
 *  "#! binary-path -i\n" (e.g., "#! /usr/local/bin/gforth-0.4.0 -i\n")
 *   padding to a multiple of 8
 *   magic: "Gforth2x" means format 0.4,
 *              where x is a byte with
 *              bit 7:   reserved = 0
 *              bit 6:5: address unit size 2^n octets
 *              bit 4:3: character size 2^n octets
 *              bit 2:1: cell size 2^n octets
 *              bit 0:   endian, big=0, little=1.
 *  The magic are always 8 octets, no matter what the native AU/character size is
 *  padding to max alignment (no padding necessary on current machines)
 *  ImageHeader structure (see below)
 *  data (size in ImageHeader.image_size)
 *  tags ((if relocatable, 1 bit/data cell)
 *
 * tag==1 means that the corresponding word is an address;
 * If the word is >=0, the address is within the image;
 * addresses within the image are given relative to the start of the image.
 * If the word =-1 (CF_NIL), the address is NIL,
 * If the word is <CF_NIL and >CF(DODOES), it's a CFA (:, Create, ...)
 * If the word =CF(DODOES), it's a DOES> CFA
 * If the word =CF(DOESJUMP), it's a DOES JUMP (2 Cells after DOES>,
 *					possibly containing a jump to dodoes)
 * If the word is <CF(DOESJUMP), it's a primitive
 */

typedef struct {
  Address base;		/* base address of image (0 if relocatable) */
  UCell checksum;	/* checksum of ca's to protect against some
			   incompatible	binary/executable combinations
			   (0 if relocatable) */
  UCell image_size;	/* all sizes in bytes */
  UCell dict_size;
  UCell data_stack_size;
  UCell fp_stack_size;
  UCell return_stack_size;
  UCell locals_stack_size;
  Xt *boot_entry;	/* initial ip for booting (in BOOT) */
  Xt *throw_entry;	/* ip after signal (in THROW) */
  Cell unused1;		/* possibly tib stack size */
  Cell unused2;
  Address data_stack_base; /* this and the following fields are initialized by the loader */
  Address fp_stack_base;
  Address return_stack_base;
  Address locals_stack_base;
} ImageHeader;
/* the image-header is created in main.fs */

void relocate(Cell *image, const char *bitstring, int size, Label symbols[])
{
  int i=0, j, k, steps=(size/sizeof(Cell))/RELINFOBITS;
  Cell token;
  char bits;
/*   static char bits[8]={0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01};*/

/*  printf("relocating %x[%x]\n", image, size); */
   
  for(k=0; k<=steps; k++)
    for(j=0, bits=bitstring[k]; j<RELINFOBITS; j++, i++, bits<<=1) {
      /*      fprintf(stderr,"relocate: image[%d]\n", i);*/
      if(bits & (1U << (RELINFOBITS-1))) {
	/* fprintf(stderr,"relocate: image[%d]=%d\n", i, image[i]);*/
	if((token=image[i])<0)
	  switch(token)
	    {
	    case CF_NIL      : image[i]=0; break;
#if !defined(DOUBLY_INDIRECT)
	    case CF(DOCOL)   :
	    case CF(DOVAR)   :
	    case CF(DOCON)   :
	    case CF(DOUSER)  : 
	    case CF(DODEFER) : 
	    case CF(DOFIELD) : MAKE_CF(image+i,symbols[CF(token)]); break;
	    case CF(DOESJUMP): MAKE_DOES_HANDLER(image+i); break;
#endif /* !defined(DOUBLY_INDIRECT) */
	    case CF(DODOES)  :
	      MAKE_DOES_CF(image+i,image[i+1]+((Cell)image));
	      break;
	    default          :
/*	      printf("Code field generation image[%x]:=CA(%x)\n",
		     i, CF(image[i])); */
	      image[i]=(Cell)CA(CF(token));
	    }
	else
	  image[i]+=(Cell)image;
      }
    }
}

UCell checksum(Label symbols[])
{
  UCell r=PRIM_VERSION;
  Cell i;

  for (i=DOCOL; i<=DOESJUMP; i++) {
    r ^= (UCell)(symbols[i]);
    r = (r << 5) | (r >> (8*sizeof(Cell)-5));
  }
#ifdef DIRECT_THREADED
  /* we have to consider all the primitives */
  for (; symbols[i]!=(Label)0; i++) {
    r ^= (UCell)(symbols[i]);
    r = (r << 5) | (r >> (8*sizeof(Cell)-5));
  }
#else
  /* in indirect threaded code all primitives are accessed through the
     symbols table, so we just have to put the base address of symbols
     in the checksum */
  r ^= (UCell)symbols;
#endif
  return r;
}

Address verbose_malloc(Cell size)
{
  Address r;
  /* leave a little room (64B) for stack underflows */
  if ((r = malloc(size+64))==NULL) {
    perror(progname);
    exit(1);
  }
  r = (Address)((((Cell)r)+(sizeof(Float)-1))&(-sizeof(Float)));
  if (debug)
    fprintf(stderr, "malloc succeeds, address=$%lx\n", (long)r);
  return r;
}

Address my_alloc(Cell size)
{
#if HAVE_MMAP
  static Address next_address=0;
  Address r;

#if defined(MAP_ANON)
  if (debug)
    fprintf(stderr,"try mmap($%lx, $%lx, ..., MAP_ANON, ...); ", (long)next_address, (long)size);
  r=mmap(next_address, size, PROT_EXEC|PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
#else /* !defined(MAP_ANON) */
  /* Ultrix (at least) does not define MAP_FILE and MAP_PRIVATE (both are
     apparently defaults) */
#ifndef MAP_FILE
# define MAP_FILE 0
#endif
#ifndef MAP_PRIVATE
# define MAP_PRIVATE 0
#endif
  static int dev_zero=-1;

  if (dev_zero == -1)
    dev_zero = open("/dev/zero", O_RDONLY);
  if (dev_zero == -1) {
    r = (Address)-1;
    if (debug)
      fprintf(stderr, "open(\"/dev/zero\"...) failed (%s), no mmap; ", 
	      strerror(errno));
  } else {
    if (debug)
      fprintf(stderr,"try mmap($%lx, $%lx, ..., MAP_FILE, dev_zero, ...); ", (long)next_address, (long)size);
    r=mmap(next_address, size, PROT_EXEC|PROT_READ|PROT_WRITE, MAP_FILE|MAP_PRIVATE, dev_zero, 0);
  }
#endif /* !defined(MAP_ANON) */

  if (r != (Address)-1) {
    if (debug)
      fprintf(stderr, "success, address=$%lx\n", (long) r);
    if (pagesize != 0)
      next_address = (Address)(((((Cell)r)+size-1)&-pagesize)+2*pagesize); /* leave one page unmapped */
    return r;
  }
  if (debug)
    fprintf(stderr, "failed: %s\n", strerror(errno));
#endif /* HAVE_MMAP */
  /* use malloc as fallback */
  return verbose_malloc(size);
}

#if (defined(mips) && !defined(INDIRECT_THREADED))
/* the 256MB jump restriction on the MIPS architecture makes the
   combination of direct threading and mmap unsafe. */
#define dict_alloc(size) verbose_malloc(size)
#else
#define dict_alloc(size) my_alloc(size)
#endif

void set_stack_sizes(ImageHeader * header)
{
  if (dictsize==0)
    dictsize = header->dict_size;
  if (dsize==0)
    dsize = header->data_stack_size;
  if (rsize==0)
    rsize = header->return_stack_size;
  if (fsize==0)
    fsize = header->fp_stack_size;
  if (lsize==0)
    lsize = header->locals_stack_size;
  dictsize=maxaligned(dictsize);
  dsize=maxaligned(dsize);
  rsize=maxaligned(rsize);
  lsize=maxaligned(lsize);
  fsize=maxaligned(fsize);
}

void alloc_stacks(ImageHeader * header)
{
  header->dict_size=dictsize;
  header->data_stack_size=dsize;
  header->fp_stack_size=fsize;
  header->return_stack_size=rsize;
  header->locals_stack_size=lsize;

  header->data_stack_base=my_alloc(dsize);
  header->fp_stack_base=my_alloc(fsize);
  header->return_stack_base=my_alloc(rsize);
  header->locals_stack_base=my_alloc(lsize);
}

int go_forth(Address image, int stack, Cell *entries)
{
  ImageHeader *image_header = (ImageHeader *)image;
  Cell *sp0=(Cell*)(image_header->data_stack_base + dsize);
  Float *fp0=(Float *)(image_header->fp_stack_base + fsize);
  Cell *rp0=(Cell *)(image_header->return_stack_base + rsize);
  Address lp0=image_header->locals_stack_base + lsize;
  Xt *ip0=(Xt *)(image_header->boot_entry);
#ifdef SYSSIGNALS
  int throw_code;
#endif

  /* ensure that the cached elements (if any) are accessible */
  IF_TOS(sp0--);
  IF_FTOS(fp0--);
  
  for(;stack>0;stack--)
    *--sp0=entries[stack-1];

#if !defined(MSDOS) && !defined(SHARC) && !defined(_WIN32) && !defined(__EMX__)
  get_winsize();
#endif
   
#ifdef SYSSIGNALS
  install_signal_handlers(); /* right place? */
  
  if ((throw_code=setjmp(throw_jmp_buf))) {
    static Cell signal_data_stack[8];
    static Cell signal_return_stack[8];
    static Float signal_fp_stack[1];

    signal_data_stack[7]=throw_code;

#ifdef GFORTH_DEBUGGING
    if (rp <= rp0 && rp > (Cell *)(image_header->return_stack_base+5)) {
      /* no rstack overflow or underflow */
      rp0 = rp;
      *--rp0 = ip;
    }
    else /* I love non-syntactic ifdefs :-) */
#endif
    rp0 = signal_return_stack+8;
    
    return((int)engine(image_header->throw_entry, signal_data_stack+7,
		       rp0, signal_fp_stack, 0));
  }
#endif

  return((int)engine(ip0,sp0,rp0,fp0,lp0));
}

#ifndef INCLUDE_IMAGE
Address loader(FILE *imagefile, char* filename)
/* returns the address of the image proper (after the preamble) */
{
  ImageHeader header;
  Address image;
  Address imp; /* image+preamble */
  Char magic[8];
  char magic7; /* size byte of magic number */
  Cell preamblesize=0;
  Label *symbols = engine(0,0,0,0,0);
  Cell data_offset = offset_image ? 56*sizeof(Cell) : 0;
  UCell check_sum;
  static char* endianstring[]= { "big","little" };
  Cell ausize = ((RELINFOBITS ==  8) ? 0 :
		 (RELINFOBITS == 16) ? 1 :
		 (RELINFOBITS == 32) ? 2 : 3);
  Cell charsize = ((sizeof(Char) == 1) ? 0 :
		   (sizeof(Char) == 2) ? 1 :
		   (sizeof(Char) == 4) ? 2 : 3) + ausize;
  Cell cellsize = ((sizeof(Cell) == 1) ? 0 :
		   (sizeof(Cell) == 2) ? 1 :
		   (sizeof(Cell) == 4) ? 2 : 3) + ausize;
  

#ifndef DOUBLY_INDIRECT
  check_sum = checksum(symbols);
#else /* defined(DOUBLY_INDIRECT) */
  check_sum = (UCell)symbols;
#endif /* defined(DOUBLY_INDIRECT) */
  
  do {
    if(fread(magic,sizeof(Char),8,imagefile) < 8) {
      fprintf(stderr,"%s: image %s doesn't seem to be a Gforth (>=0.4) image.\n",
	      progname, filename);
      exit(1);
    }
    preamblesize+=8;
  } while(memcmp(magic,"Gforth2",7));
  magic7 = magic[7];
  if (debug) {
    magic[7]='\0';
    fprintf(stderr,"Magic found: %s $%x\n", magic, magic7);
  }

  if(magic7 != (ausize << 5) + (charsize << 3) + (cellsize << 1) +
#ifdef WORDS_BIGENDIAN
       0
#else
       1
#endif
       )
    { fprintf(stderr,"This image is %d bit cell, %d bit char, %d bit address unit %s-endian,\n"
	      "whereas the machine is %d bit cell, %d bit char, %d bit address unit, %s-endian.\n", 
	      (1<<((magic7>>1)&3))*8,
	      (1<<((magic7>>3)&3))*8,
	      (1<<((magic7>>5)&3))*8,
	      endianstring[magic7&1],
	      (1<<cellsize)*8,
	      (1<<charsize)*8,
	      (1<<ausize)*8,
	      endianstring[
#ifdef WORDS_BIGENDIAN
		      0
#else
		      1
#endif
		      ]);
      exit(-2);
    };

  fread((void *)&header,sizeof(ImageHeader),1,imagefile);

  set_stack_sizes(&header);
  
#if HAVE_GETPAGESIZE
  pagesize=getpagesize(); /* Linux/GNU libc offers this */
#elif HAVE_SYSCONF && defined(_SC_PAGESIZE)
  pagesize=sysconf(_SC_PAGESIZE); /* POSIX.4 */
#elif PAGESIZE
  pagesize=PAGESIZE; /* in limits.h according to Gallmeister's POSIX.4 book */
#endif
  if (debug)
    fprintf(stderr,"pagesize=%ld\n",(unsigned long) pagesize);

  image = dict_alloc(preamblesize+dictsize+data_offset)+data_offset;
  rewind(imagefile);  /* fseek(imagefile,0L,SEEK_SET); */
  if (clear_dictionary)
    memset(image, 0, dictsize);
  fread(image, 1, preamblesize+header.image_size, imagefile);
  imp=image+preamblesize;
  if(header.base==0) {
    Cell reloc_size=((header.image_size-1)/sizeof(Cell))/8+1;
    char reloc_bits[reloc_size];
    fread(reloc_bits, 1, reloc_size, imagefile);
    relocate((Cell *)imp, reloc_bits, header.image_size, symbols);
#if 0
    { /* let's see what the relocator did */
      FILE *snapshot=fopen("snapshot.fi","wb");
      fwrite(image,1,imagesize,snapshot);
      fclose(snapshot);
    }
#endif
  }
  else if(header.base!=imp) {
    fprintf(stderr,"%s: Cannot load nonrelocatable image (compiled for address $%lx) at address $%lx\n",
	    progname, (unsigned long)header.base, (unsigned long)imp);
    exit(1);
  }
  if (header.checksum==0)
    ((ImageHeader *)imp)->checksum=check_sum;
  else if (header.checksum != check_sum) {
    fprintf(stderr,"%s: Checksum of image ($%lx) does not match the executable ($%lx)\n",
	    progname, (unsigned long)(header.checksum),(unsigned long)check_sum);
    exit(1);
  }
  fclose(imagefile);

  alloc_stacks((ImageHeader *)imp);

  CACHE_FLUSH(imp, header.image_size);

  return imp;
}

int onlypath(char *file)
{
  int i;
  i=strlen(file);
  while (i) {
    if (file[i]=='\\' || file[i]=='/') break;
    i--;
  }
  return i;
}

FILE *openimage(char *fullfilename)
{
  FILE *image_file;

  image_file=fopen(fullfilename,"rb");
  if (image_file!=NULL && debug)
    fprintf(stderr, "Opened image file: %s\n", fullfilename);
  return image_file;
}

FILE *checkimage(char *path, int len, char *imagename)
{
  int dirlen=len;
  char fullfilename[dirlen+strlen(imagename)+2];

  memcpy(fullfilename, path, dirlen);
  if (fullfilename[dirlen-1]!='/')
    fullfilename[dirlen++]='/';
  strcpy(fullfilename+dirlen,imagename);
  return openimage(fullfilename);
}

FILE * open_image_file(char * imagename, char * path)
{
  FILE * image_file=NULL;
  
  if(strchr(imagename, '/')==NULL) {
    /* first check the directory where the exe file is in !! 01may97jaw */
    if (onlypath(progname))
      image_file=checkimage(progname, onlypath(progname), imagename);
    if (!image_file)
      do {
	char *pend=strchr(path, PATHSEP);
	if (pend==NULL)
	  pend=path+strlen(path);
	if (strlen(path)==0) break;
	image_file=checkimage(path, pend-path, imagename);
	path=pend+(*pend==PATHSEP);
      } while (image_file==NULL);
  } else {
    image_file=openimage(imagename);
  }

  if (!image_file) {
    fprintf(stderr,"%s: cannot open image file %s in path %s for reading\n",
	    progname, imagename, path);
    exit(1);
  }

  return image_file;
}
#endif

#ifdef HAS_OS
UCell convsize(char *s, UCell elemsize)
/* converts s of the format [0-9]+[bekMGT]? (e.g. 25k) into the number
   of bytes.  the letter at the end indicates the unit, where e stands
   for the element size. default is e */
{
  char *endp;
  UCell n,m;

  m = elemsize;
  n = strtoul(s,&endp,0);
  if (endp!=NULL) {
    if (strcmp(endp,"b")==0)
      m=1;
    else if (strcmp(endp,"k")==0)
      m=1024;
    else if (strcmp(endp,"M")==0)
      m=1024*1024;
    else if (strcmp(endp,"G")==0)
      m=1024*1024*1024;
    else if (strcmp(endp,"T")==0) {
#if (SIZEOF_CHAR_P > 4)
      m=1024*1024*1024*1024;
#else
      fprintf(stderr,"%s: size specification \"%s\" too large for this machine\n", progname, endp);
      exit(1);
#endif
    } else if (strcmp(endp,"e")!=0 && strcmp(endp,"")!=0) {
      fprintf(stderr,"%s: cannot grok size specification %s: invalid unit \"%s\"\n", progname, s, endp);
      exit(1);
    }
  }
  return n*m;
}

void gforth_args(int argc, char ** argv, char ** path, char ** imagename)
{
  int c;

  opterr=0;
  while (1) {
    int option_index=0;
    static struct option opts[] = {
      {"image-file", required_argument, NULL, 'i'},
      {"dictionary-size", required_argument, NULL, 'm'},
      {"data-stack-size", required_argument, NULL, 'd'},
      {"return-stack-size", required_argument, NULL, 'r'},
      {"fp-stack-size", required_argument, NULL, 'f'},
      {"locals-stack-size", required_argument, NULL, 'l'},
      {"path", required_argument, NULL, 'p'},
      {"version", no_argument, NULL, 'v'},
      {"help", no_argument, NULL, 'h'},
      /* put something != 0 into offset_image */
      {"offset-image", no_argument, &offset_image, 1},
      {"no-offset-im", no_argument, &offset_image, 0},
      {"clear-dictionary", no_argument, &clear_dictionary, 1},
      {"die-on-signal", no_argument, &die_on_signal, 1},
      {"debug", no_argument, &debug, 1},
      {0,0,0,0}
      /* no-init-file, no-rc? */
    };
    
    c = getopt_long(argc, argv, "+i:m:d:r:f:l:p:vh", opts, &option_index);
    
    if (c==EOF)
      break;
    if (c=='?') {
      optind--;
      break;
    }
    switch (c) {
    case 'i': *imagename = optarg; break;
    case 'm': dictsize = convsize(optarg,sizeof(Cell)); break;
    case 'd': dsize = convsize(optarg,sizeof(Cell)); break;
    case 'r': rsize = convsize(optarg,sizeof(Cell)); break;
    case 'f': fsize = convsize(optarg,sizeof(Float)); break;
    case 'l': lsize = convsize(optarg,sizeof(Cell)); break;
    case 'p': *path = optarg; break;
    case 'v': fprintf(stderr, "gforth %s\n", VERSION); exit(0);
    case 'h': 
      fprintf(stderr, "Usage: %s [engine options] [image arguments]\n\
Engine Options:\n\
  --clear-dictionary		    Initialize the dictionary with 0 bytes\n\
  -d SIZE, --data-stack-size=SIZE   Specify data stack size\n\
  --debug			    Print debugging information during startup\n\
  --die-on-signal		    exit instead of CATCHing some signals\n\
  -f SIZE, --fp-stack-size=SIZE	    Specify floating point stack size\n\
  -h, --help			    Print this message and exit\n\
  -i FILE, --image-file=FILE	    Use image FILE instead of `gforth.fi'\n\
  -l SIZE, --locals-stack-size=SIZE Specify locals stack size\n\
  -m SIZE, --dictionary-size=SIZE   Specify Forth dictionary size\n\
  --no-offset-im		    Load image at normal position\n\
  --offset-image		    Load image at a different position\n\
  -p PATH, --path=PATH		    Search path for finding image and sources\n\
  -r SIZE, --return-stack-size=SIZE Specify return stack size\n\
  -v, --version			    Print version and exit\n\
SIZE arguments consist of an integer followed by a unit. The unit can be\n\
  `b' (byte), `e' (element; default), `k' (KB), `M' (MB), `G' (GB) or `T' (TB).\n",
	      argv[0]);
      optind--;
      return;
      exit(0);
    }
  }
}
#endif

#ifdef INCLUDE_IMAGE
extern Cell image[];
extern const char reloc_bits[];
#endif

int main(int argc, char **argv, char **env)
{
  char *path = getenv("GFORTHPATH") ? : DEFAULTPATH;
#ifndef INCLUDE_IMAGE
  char *imagename="gforth.fi";
  FILE *image_file;
  Address image;
#endif
  int retvalue;
	  
#if defined(i386) && defined(ALIGNMENT_CHECK) && !defined(DIRECT_THREADED)
  /* turn on alignment checks on the 486.
   * on the 386 this should have no effect. */
  __asm__("pushfl; popl %eax; orl $0x40000, %eax; pushl %eax; popfl;");
  /* this is unusable with Linux' libc.4.6.27, because this library is
     not alignment-clean; we would have to replace some library
     functions (e.g., memcpy) to make it work. Also GCC doesn't try to keep
     the stack FP-aligned. */
#endif

  /* buffering of the user output device */
#ifdef _IONBF
  if (isatty(fileno(stdout))) {
    fflush(stdout);
    setvbuf(stdout,NULL,_IONBF,0);
  }
#endif

  progname = argv[0];

#ifdef HAS_OS
  gforth_args(argc, argv, &path, &imagename);
#endif

#ifdef INCLUDE_IMAGE
  set_stack_sizes((ImageHeader *)image);
  relocate(image, reloc_bits, ((ImageHeader*)&image)->image_size, (Label*)engine(0, 0, 0, 0, 0));
  alloc_stacks((ImageHeader *)image);
#else
  image_file = open_image_file(imagename, path);
  image = loader(image_file, imagename);
#endif

  {
    char path2[strlen(path)+1];
    char *p1, *p2;
    Cell environ[]= {
      (Cell)argc-(optind-1),
      (Cell)(argv+(optind-1)),
      (Cell)strlen(path),
      (Cell)path2};
    argv[optind-1] = progname;
    /*
       for (i=0; i<environ[0]; i++)
       printf("%s\n", ((char **)(environ[1]))[i]);
       */
    /* make path OS-independent by replacing path separators with NUL */
    for (p1=path, p2=path2; *p1!='\0'; p1++, p2++)
      if (*p1==PATHSEP)
	*p2 = '\0';
      else
	*p2 = *p1;
    *p2='\0';
    retvalue = go_forth(image, 4, environ);
    deprep_terminal();
  }
  return retvalue;
}