File: execute.c

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/********************************************
execute.c
copyright 1991-1996, Michael D. Brennan

This is a source file for mawk, an implementation of
the AWK programming language.

Mawk is distributed without warranty under the terms of
the GNU General Public License, version 2, 1991.
********************************************/

/* $Log: execute.c,v $
 * Revision 1.13  1996/02/01  04:39:40  mike
 * dynamic array scheme
 *
 * Revision 1.12  1995/06/06  00:18:24  mike
 * change mawk_exit(1) to mawk_exit(2)
 *
 * Revision 1.11  1995/03/08  00:06:24  mike
 * add a pointer cast
 *
 * Revision 1.10  1994/12/13  00:12:10  mike
 * delete A statement to delete all of A at once
 *
 * Revision 1.9  1994/10/25  23:36:11  mike
 * clear aloop stack on _NEXT
 *
 * Revision 1.8  1994/10/08  19:15:35  mike
 * remove SM_DOS
 *
 * Revision 1.7  1993/12/30  19:10:03  mike
 * minor cleanup to _CALL
 *
 * Revision 1.6  1993/12/01  14:25:13  mike
 * reentrant array loops
 *
 * Revision 1.5  1993/07/22  00:04:08  mike
 * new op code _LJZ _LJNZ
 *
 * Revision 1.4  1993/07/14  12:18:21  mike
 * run thru indent
 *
 * Revision 1.3	 1993/07/14  11:50:17  mike
 * rm SIZE_T and void casts
 *
 * Revision 1.2	 1993/07/04  12:51:49  mike
 * start on autoconfig changes
 *
 * Revision 5.10  1993/02/13  21:57:22	mike
 * merge patch3
 *
 * Revision 5.9	 1993/01/07  02:50:33  mike
 * relative vs absolute code
 *
 * Revision 5.8	 1993/01/01  21:30:48  mike
 * split new_STRING() into new_STRING and new_STRING0
 *
 * Revision 5.7.1.1  1993/01/15	 03:33:39  mike
 * patch3: safer double to int conversion
 *
 * Revision 5.7	 1992/12/17  02:48:01  mike
 * 1.1.2d changes for DOS
 *
 * Revision 5.6	 1992/11/29  18:57:50  mike
 * field expressions convert to long so 16 bit and 32 bit
 * systems behave the same
 *
 * Revision 5.5	 1992/08/11  15:24:55  brennan
 * patch2: F_PUSHA and FE_PUSHA
 * If this is preparation for g?sub(r,s,$expr) or (++|--) on $expr,
 * then if expr > NF, make sure $expr is set to ""
 *
 * Revision 5.4	 1992/08/11  14:51:54  brennan
 * patch2:  $expr++ is numeric even if $expr is string.
 * I forgot to do this earlier when handling x++ case.
 *
 * Revision 5.3	 1992/07/08  17:03:30  brennan
 * patch 2
 * revert to version 1.0 comparisons, i.e.
 * page 44-45 of AWK book
 *
 * Revision 5.2	 1992/04/20  21:40:40  brennan
 * patch 2
 * x++ is numeric, even if x is string
 *
 * Revision 5.1	 1991/12/05  07:55:50  brennan
 * 1.1 pre-release
 *
*/


#include "mawk.h"
#include "code.h"
#include "memory.h"
#include "symtype.h"
#include "field.h"
#include "bi_funct.h"
#include "bi_vars.h"
#include "regexp.h"
#include "repl.h"
#include "fin.h"
#include <math.h>

static int PROTO(compare, (CELL *)) ;
static int PROTO(d_to_index, (double)) ;

#ifdef	 NOINFO_SIGFPE
static char dz_msg[] = "division by zero" ;
#define	 CHECK_DIVZERO(x) if( (x) == 0.0 )rt_error(dz_msg);else
#endif

#ifdef	 DEBUG
static void PROTO(eval_overflow, (void)) ;

#define	 inc_sp()   if( ++sp == eval_stack+EVAL_STACK_SIZE )\
			 eval_overflow()
#else

/* If things are working, the eval stack should not overflow */

#define inc_sp()    sp++
#endif

#define	 SAFETY	   16
#define	 DANGER	   (EVAL_STACK_SIZE-SAFETY)

/*  The stack machine that executes the code */

CELL eval_stack[EVAL_STACK_SIZE] ;
/* these can move for deep recursion */
static CELL *stack_base = eval_stack ;
static CELL *stack_danger = eval_stack + DANGER ;

#ifdef	DEBUG
static void
eval_overflow()
{
   overflow("eval stack", EVAL_STACK_SIZE) ;
}
#endif

/* holds info for array loops (on a stack) */
typedef struct aloop_state {
   struct aloop_state *link ;
   CELL *var ;  /* for(var in A) */
   STRING **base ;
   STRING **ptr ;
   STRING **limit ;
} ALOOP_STATE ;

/* clean up aloop stack on next, return, exit */
#define CLEAR_ALOOP_STACK() if(aloop_state){\
	    clear_aloop_stack(aloop_state);\
	    aloop_state=(ALOOP_STATE*)0;}else

static void clear_aloop_stack(top)
   ALOOP_STATE *top ;
{
   ALOOP_STATE *q ;

   do {
      while(top->ptr<top->limit) {
	 free_STRING(*top->ptr) ;
	 top->ptr++ ;
      }
      if (top->base < top->limit)
	 zfree(top->base, (top->limit-top->base)*sizeof(STRING*)) ;
      q = top ; top = q->link ;
      ZFREE(q) ;
   } while (top) ;
}
   

static INST *restart_label ;	 /* control flow labels */
INST *next_label ;
static CELL tc ;		 /*useful temp */

void
execute(cdp, sp, fp)
   register INST *cdp ;		 /* code ptr, start execution here */
   register CELL *sp ;		 /* eval_stack pointer */
   CELL *fp ;			 /* frame ptr into eval_stack for
			   user defined functions */
{
   /* some useful temporaries */
   CELL *cp ;
   int t ;

   /* save state for array loops via a stack */
   ALOOP_STATE *aloop_state = (ALOOP_STATE*) 0 ;

   /* for moving the eval stack on deep recursion */
   CELL *old_stack_base ;
   CELL *old_sp ;

#ifdef	DEBUG
   CELL *entry_sp = sp ;
#endif


   if (fp)
   {
      /* we are a function call, check for deep recursion */
      if (sp > stack_danger)
      {				/* change stacks */
	 old_stack_base = stack_base ;
	 old_sp = sp ;
	 stack_base = (CELL *) zmalloc(sizeof(CELL) * EVAL_STACK_SIZE) ;
	 stack_danger = stack_base + DANGER ;
	 sp = stack_base ;
	 /* waste 1 slot for ANSI, actually large model msdos breaks in
	     RET if we don't */
#ifdef	DEBUG
	 entry_sp = sp ;
#endif
      }
      else  old_stack_base = (CELL *) 0 ;
   }

   while (1)
      switch (cdp++->op)
      {

/* HALT only used by the disassemble now ; this remains
   so compilers don't offset the jump table */
	 case _HALT:

	 case _STOP:		/* only for range patterns */
#ifdef	DEBUG
	    if (sp != entry_sp + 1)  bozo("stop0") ;
#endif
	    return ;

	 case _PUSHC:
	    inc_sp() ;
	    cellcpy(sp, cdp++->ptr) ;
	    break ;

	 case _PUSHD:
	    inc_sp() ;
	    sp->type = C_DOUBLE ;
	    sp->dval = *(double *) cdp++->ptr ;
	    break ;

	 case _PUSHS:
	    inc_sp() ;
	    sp->type = C_STRING ;
	    sp->ptr = cdp++->ptr ;
	    string(sp)->ref_cnt++ ;
	    break ;

	 case F_PUSHA:
	    cp = (CELL *) cdp->ptr ;
	    if (cp != field)
	    {
	       if (nf < 0)  split_field0() ;

	       if (!(
#ifdef MSDOS
		       SAMESEG(cp, field) &&
#endif
		       cp >= NF && cp <= LAST_PFIELD))
	       {
		  /* its a real field $1, $2 ...
		     If its greater than $NF, we have to
		     make sure its set to ""  so that
		     (++|--) and g?sub() work right
		  */
		  t = field_addr_to_index(cp) ;
		  if (t > nf)
		  {
		     cell_destroy(cp) ;
		     cp->type = C_STRING ;
		     cp->ptr = (PTR) & null_str ;
		     null_str.ref_cnt++ ;
		  }
	       }
	    }
	    /* fall thru */

	 case _PUSHA:
	 case A_PUSHA:
	    inc_sp() ;
	    sp->ptr = cdp++->ptr ;
	    break ;

	 case _PUSHI:
	    /* put contents of next address on stack*/
	    inc_sp() ;
	    cellcpy(sp, cdp++->ptr) ;
	    break ;

	 case L_PUSHI:
	    /* put the contents of a local var on stack,
	       cdp->op holds the offset from the frame pointer */
	    inc_sp() ;
	    cellcpy(sp, fp + cdp++->op) ;
	    break ;

	 case L_PUSHA:
	    /* put a local address on eval stack */
	    inc_sp() ;
	    sp->ptr = (PTR) (fp + cdp++->op) ;
	    break ;


	 case F_PUSHI:

	    /* push contents of $i
	       cdp[0] holds & $i , cdp[1] holds i */

	    inc_sp() ;
	    if (nf < 0)	 split_field0() ;
	    cp = (CELL *) cdp->ptr ;
	    t = (cdp + 1)->op ;
	    cdp += 2 ;

	    if (t <= nf)  cellcpy(sp, cp) ;
	    else  /* an unset field */
	    {
	       sp->type = C_STRING ;
	       sp->ptr = (PTR) & null_str ;
	       null_str.ref_cnt++ ;
	    }
	    break ;

	 case NF_PUSHI:

	    inc_sp() ;
	    if (nf < 0)	 split_field0() ;
	    cellcpy(sp, NF) ;
	    break ;

	 case FE_PUSHA:

	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;

	    t = d_to_index(sp->dval) ;
	    if (t && nf < 0)  split_field0() ;
	    sp->ptr = (PTR) field_ptr(t) ;
	    if (t > nf)
	    {
	       /* make sure its set to "" */
	       cp = (CELL *) sp->ptr ;
	       cell_destroy(cp) ;
	       cp->type = C_STRING ;
	       cp->ptr = (PTR) & null_str ;
	       null_str.ref_cnt++ ;
	    }
	    break ;

	 case FE_PUSHI:

	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;

	    t = d_to_index(sp->dval) ;

	    if (nf < 0)	 split_field0() ;
	    if (t <= nf)  cellcpy(sp, field_ptr(t)) ;
	    else
	    {
	       sp->type = C_STRING ;
	       sp->ptr = (PTR) & null_str ;
	       null_str.ref_cnt++ ;
	    }
	    break ;


	 case AE_PUSHA:
	    /* top of stack has an expr, cdp->ptr points at an
	   array, replace the expr with the cell address inside
	   the array */

	    cp = array_find((ARRAY) cdp++->ptr, sp, CREATE) ;
	    cell_destroy(sp) ;
	    sp->ptr = (PTR) cp ;
	    break ;

	 case AE_PUSHI:
	    /* top of stack has an expr, cdp->ptr points at an
	   array, replace the expr with the contents of the
	   cell inside the array */

	    cp = array_find((ARRAY) cdp++->ptr, sp, CREATE) ;
	    cell_destroy(sp) ;
	    cellcpy(sp, cp) ;
	    break ;

	 case LAE_PUSHI:
	    /*	sp[0] is an expression
	    cdp->op is offset from frame pointer of a CELL which
	       has an ARRAY in the ptr field, replace expr
	    with  array[expr]
	*/
	    cp = array_find((ARRAY) fp[cdp++->op].ptr, sp, CREATE) ;
	    cell_destroy(sp) ;
	    cellcpy(sp, cp) ;
	    break ;

	 case LAE_PUSHA:
	    /*	sp[0] is an expression
	    cdp->op is offset from frame pointer of a CELL which
	       has an ARRAY in the ptr field, replace expr
	    with  & array[expr]
	*/
	    cp = array_find((ARRAY) fp[cdp++->op].ptr, sp, CREATE) ;
	    cell_destroy(sp) ;
	    sp->ptr = (PTR) cp ;
	    break ;

	 case LA_PUSHA:
	    /*	cdp->op is offset from frame pointer of a CELL which
	       has an ARRAY in the ptr field. Push this ARRAY
	       on the eval stack
	*/
	    inc_sp() ;
	    sp->ptr = fp[cdp++->op].ptr ;
	    break ;

	 case SET_ALOOP:
	    {
	       ALOOP_STATE *ap = ZMALLOC(ALOOP_STATE) ;
	       unsigned vector_size ;

	       ap->var = (CELL *) sp[-1].ptr ;
	       ap->base = ap->ptr = array_loop_vector(
			    (ARRAY)sp->ptr, &vector_size) ;
	       ap->limit = ap->base + vector_size ;
	       sp -= 2 ;

	       /* push onto aloop stack */
	       ap->link = aloop_state ;
	       aloop_state = ap ;
	       cdp += cdp->op ;
	    }
	    break ;

	 case  ALOOP :
	    {
	       ALOOP_STATE *ap = aloop_state ;
	       if (ap->ptr < ap->limit) 
	       {
		  cell_destroy(ap->var) ;
		  ap->var->type = C_STRING ;
		  ap->var->ptr = (PTR) *ap->ptr++ ;
		  cdp += cdp->op ;
	       }
	       else cdp++ ;
	    }
	    break ;
		  
	 case  POP_AL :
	    { 
	       /* finish up an array loop */
	       ALOOP_STATE *ap = aloop_state ;
               aloop_state = ap->link ;
	       while(ap->ptr < ap->limit) {
		  free_STRING(*ap->ptr) ;
		  ap->ptr++ ;
	       }
	       if (ap->base < ap->limit)
		  zfree(ap->base,(ap->limit-ap->base)*sizeof(STRING*)) ;
               ZFREE(ap) ;
            }
	    break ;

	 case _POP:
	    cell_destroy(sp) ;
	    sp-- ;
	    break ;

	 case _ASSIGN:
	    /* top of stack has an expr, next down is an
	       address, put the expression in *address and
	       replace the address with the expression */

	    /* don't propagate type C_MBSTRN */
	    if (sp->type == C_MBSTRN)  check_strnum(sp) ;
	    sp-- ;
	    cell_destroy(((CELL *) sp->ptr)) ;
	    cellcpy(sp, cellcpy(sp->ptr, sp + 1)) ;
	    cell_destroy(sp + 1) ;
	    break ;

	 case F_ASSIGN:
	    /* assign to a field  */
	    if (sp->type == C_MBSTRN)  check_strnum(sp) ;
	    sp-- ;
	    field_assign((CELL *) sp->ptr, sp + 1) ;
	    cell_destroy(sp + 1) ;
	    cellcpy(sp, (CELL *) sp->ptr) ;
	    break ;

	 case _ADD_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;

#if SW_FP_CHECK			/* specific to V7 and XNX23A */
	    clrerr() ;
#endif
	    cp->dval += sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	 case _SUB_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    cp->dval -= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	 case _MUL_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    cp->dval *= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	 case _DIV_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp->dval) ;
#endif

#if SW_FP_CHECK
	    clrerr() ;
#endif
	    cp->dval /= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	 case _MOD_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp->dval) ;
#endif

	    cp->dval = fmod(cp->dval, sp--->dval) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	 case _POW_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
	    cp->dval = pow(cp->dval, sp--->dval) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    break ;

	    /* will anyone ever use these ? */

	 case F_ADD_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    tc.dval += sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_SUB_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    tc.dval -= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_MUL_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    tc.dval *= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_DIV_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp->dval) ;
#endif

#if SW_FP_CHECK
	    clrerr() ;
#endif
	    tc.dval /= sp--->dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_MOD_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp->dval) ;
#endif

	    tc.dval = fmod(tc.dval, sp--->dval) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_POW_ASG:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    cp = (CELL *) (sp - 1)->ptr ;
	    cast1_to_d(cellcpy(&tc, cp)) ;
	    tc.dval = pow(tc.dval, sp--->dval) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    field_assign(cp, &tc) ;
	    break ;

	 case _ADD:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    sp[0].dval += sp[1].dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    break ;

	 case _SUB:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    sp[0].dval -= sp[1].dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    break ;

	 case _MUL:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;
#if SW_FP_CHECK
	    clrerr() ;
#endif
	    sp[0].dval *= sp[1].dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    break ;

	 case _DIV:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp[1].dval) ;
#endif

#if SW_FP_CHECK
	    clrerr() ;
#endif
	    sp[0].dval /= sp[1].dval ;
#if SW_FP_CHECK
	    fpcheck() ;
#endif
	    break ;

	 case _MOD:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;

#if  NOINFO_SIGFPE
	    CHECK_DIVZERO(sp[1].dval) ;
#endif

	    sp[0].dval = fmod(sp[0].dval, sp[1].dval) ;
	    break ;

	 case _POW:
	    sp-- ;
	    if (TEST2(sp) != TWO_DOUBLES)  cast2_to_d(sp) ;
	    sp[0].dval = pow(sp[0].dval, sp[1].dval) ;
	    break ;

	 case _NOT:
	    /* evaluates to 0.0 or 1.0 */
	  reswitch_1:
	    switch (sp->type)
	    {
	       case C_NOINIT:
		  sp->dval = 1.0 ; break ;
	       case C_DOUBLE:
		  sp->dval = sp->dval != 0.0 ? 0.0 : 1.0 ;
		  break ;
	       case C_STRING:
		  sp->dval = string(sp)->len ? 0.0 : 1.0 ;
		  free_STRING(string(sp)) ;
		  break ;
	       case C_STRNUM:	/* test as a number */
		  sp->dval = sp->dval != 0.0 ? 0.0 : 1.0 ;
		  free_STRING(string(sp)) ;
		  break ;
	       case C_MBSTRN:
		  check_strnum(sp) ;
		  goto reswitch_1 ;
	       default:
		  bozo("bad type on eval stack") ;
	    }
	    sp->type = C_DOUBLE ;
	    break ;

	 case _TEST:
	    /* evaluates to 0.0 or 1.0 */
	  reswitch_2:
	    switch (sp->type)
	    {
	       case C_NOINIT:
		  sp->dval = 0.0 ; break ;
	       case C_DOUBLE:
		  sp->dval = sp->dval != 0.0 ? 1.0 : 0.0 ;
		  break ;
	       case C_STRING:
		  sp->dval = string(sp)->len ? 1.0 : 0.0 ;
		  free_STRING(string(sp)) ;
		  break ;
	       case C_STRNUM:	/* test as a number */
		  sp->dval = sp->dval != 0.0 ? 1.0 : 0.0 ;
		  free_STRING(string(sp)) ;
		  break ;
	       case C_MBSTRN:
		  check_strnum(sp) ;
		  goto reswitch_2 ;
	       default:
		  bozo("bad type on eval stack") ;
	    }
	    sp->type = C_DOUBLE ;
	    break ;

	 case _UMINUS:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    sp->dval = -sp->dval ;
	    break ;

	 case _UPLUS:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    break ;

	 case _CAT:
	    {
	       unsigned len1, len2 ;
	       char *str1, *str2 ;
	       STRING *b ;

	       sp-- ;
	       if (TEST2(sp) != TWO_STRINGS)  cast2_to_s(sp) ;
	       str1 = string(sp)->str ;
	       len1 = string(sp)->len ;
	       str2 = string(sp + 1)->str ;
	       len2 = string(sp + 1)->len ;

	       b = new_STRING0(len1 + len2) ;
	       memcpy(b->str, str1, len1) ;
	       memcpy(b->str + len1, str2, len2) ;
	       free_STRING(string(sp)) ;
	       free_STRING(string(sp + 1)) ;

	       sp->ptr = (PTR) b ;
	       break ;
	    }

	 case _PUSHINT:
	    inc_sp() ;
	    sp->type = cdp++->op ;
	    break ;

	 case _BUILTIN:
	 case _PRINT:
	    sp = (*(PF_CP) cdp++->ptr) (sp) ;
	    break ;

	 case _POST_INC:
	    cp = (CELL *) sp->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    cp->dval += 1.0 ;
	    break ;

	 case _POST_DEC:
	    cp = (CELL *) sp->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = cp->dval ;
	    cp->dval -= 1.0 ;
	    break ;

	 case _PRE_INC:
	    cp = (CELL *) sp->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
	    sp->dval = cp->dval += 1.0 ;
	    sp->type = C_DOUBLE ;
	    break ;

	 case _PRE_DEC:
	    cp = (CELL *) sp->ptr ;
	    if (cp->type != C_DOUBLE)  cast1_to_d(cp) ;
	    sp->dval = cp->dval -= 1.0 ;
	    sp->type = C_DOUBLE ;
	    break ;


	 case F_POST_INC:
	    cp = (CELL *) sp->ptr ;
	    cellcpy(&tc, cp) ;
	    cast1_to_d(&tc) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    tc.dval += 1.0 ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_POST_DEC:
	    cp = (CELL *) sp->ptr ;
	    cellcpy(&tc, cp) ;
	    cast1_to_d(&tc) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = tc.dval ;
	    tc.dval -= 1.0 ;
	    field_assign(cp, &tc) ;
	    break ;

	 case F_PRE_INC:
	    cp = (CELL *) sp->ptr ;
	    cast1_to_d(cellcpy(sp, cp)) ;
	    sp->dval += 1.0 ;
	    field_assign(cp, sp) ;
	    break ;

	 case F_PRE_DEC:
	    cp = (CELL *) sp->ptr ;
	    cast1_to_d(cellcpy(sp, cp)) ;
	    sp->dval -= 1.0 ;
	    field_assign(cp, sp) ;
	    break ;

	 case _JMP:
	    cdp += cdp->op ;
	    break ;

	 case _JNZ:
	    /* jmp if top of stack is non-zero and pop stack */
	    if (test(sp))  cdp += cdp->op ;
	    else  cdp++ ;
	    cell_destroy(sp) ;
	    sp-- ;
	    break ;

	 case _JZ:
	    /* jmp if top of stack is zero and pop stack */
	    if (!test(sp))  cdp += cdp->op ;
	    else  cdp++ ;
	    cell_destroy(sp) ;
	    sp-- ;
	    break ;

	 case _LJZ:
	    /* special jump for logical and */
	    /* this is always preceded by _TEST */
	    if ( sp->dval == 0.0 )
	    {
	       /* take jump, but don't pop stack */
	       cdp += cdp->op ;
	    }
	    else
	    {
	       /* pop and don't jump */
	       sp-- ;
	       cdp++ ;
	    }
	    break ;
	       
	 case _LJNZ:
	    /* special jump for logical or */
	    /* this is always preceded by _TEST */
	    if ( sp->dval != 0.0 )
	    {
	       /* take jump, but don't pop stack */
	       cdp += cdp->op ;
	    }
	    else
	    {
	       /* pop and don't jump */
	       sp-- ;
	       cdp++ ;
	    }
	    break ;

	    /*	the relation operations */
	    /*	compare() makes sure string ref counts are OK */
	 case _EQ:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t == 0 ? 1.0 : 0.0 ;
	    break ;

	 case _NEQ:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t ? 1.0 : 0.0 ;
	    break ;

	 case _LT:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t < 0 ? 1.0 : 0.0 ;
	    break ;

	 case _LTE:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t <= 0 ? 1.0 : 0.0 ;
	    break ;

	 case _GT:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t > 0 ? 1.0 : 0.0 ;
	    break ;

	 case _GTE:
	    t = compare(--sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t >= 0 ? 1.0 : 0.0 ;
	    break ;

	 case _MATCH0:
	    /* does $0 match, the RE at cdp? */

	    inc_sp() ;
	    if (field->type >= C_STRING)
	    {
	       sp->type = C_DOUBLE ;
	       sp->dval = REtest(string(field)->str, cdp++->ptr)
		  ? 1.0 : 0.0 ;

	       break /* the case */ ;
	    }
	    else
	    {
	       cellcpy(sp, field) ;
	       /* and FALL THRU */
	    }

	 case _MATCH1:
	    /* does expr at sp[0] match RE at cdp */
	    if (sp->type < C_STRING)  cast1_to_s(sp) ;
	    t = REtest(string(sp)->str, cdp++->ptr) ;
	    free_STRING(string(sp)) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t ? 1.0 : 0.0 ;
	    break ;


	 case _MATCH2:
	    /* does sp[-1] match sp[0] as re */
	    cast_to_RE(sp) ;

	    if ((--sp)->type < C_STRING)  cast1_to_s(sp) ;
	    t = REtest(string(sp)->str, (sp + 1)->ptr) ;

	    free_STRING(string(sp)) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = t ? 1.0 : 0.0 ;
	    break ;

	 case A_TEST:
	    /* entry :	sp[0].ptr-> an array
		    sp[-1]  is an expression

	   we compute	(expression in array)  */
	    sp-- ;
	    cp = array_find((sp + 1)->ptr, sp, NO_CREATE) ;
	    cell_destroy(sp) ;
	    sp->type = C_DOUBLE ;
	    sp->dval = (cp != (CELL *) 0) ? 1.0 : 0.0 ;
	    break ;

	 case A_DEL:
	    /* sp[0].ptr ->  array
	   sp[-1] is an expr
	   delete  array[expr]	*/

	    array_delete(sp->ptr, sp - 1) ;
	    cell_destroy(sp - 1) ;
	    sp -= 2 ;
	    break ;

	 case DEL_A:
	    /* free all the array at once */
	    array_clear(sp->ptr) ;
	    sp-- ;
	    break ;

	    /* form a multiple array index */
	 case A_CAT:
	    sp = array_cat(sp, cdp++->op) ;
	    break ;

	 case _EXIT:
	    if (sp->type != C_DOUBLE)  cast1_to_d(sp) ;
	    exit_code = d_to_i(sp->dval) ;
	    sp-- ;
	    /* fall thru */

	 case _EXIT0:

	    if (!end_start)  mawk_exit(exit_code) ;

	    cdp = end_start ;
	    end_start = (INST *) 0 ;	 /* makes sure next exit exits */

	    if (begin_start)  zfree(begin_start, begin_size) ;
	    if (main_start)  zfree(main_start, main_size) ;
	    sp = eval_stack - 1 ;/* might be in user function */
	    CLEAR_ALOOP_STACK() ; /* ditto */
	    break ;

	 case _JMAIN:		/* go from BEGIN code to MAIN code */
	    zfree(begin_start, begin_size) ;
	    begin_start = (INST *) 0 ;
	    cdp = main_start ;
	    break ;

	 case _OMAIN:
	    if (!main_fin)  open_main() ;
	    restart_label = cdp ;
	    cdp = next_label ;
	    break ;

	 case _NEXT:
	    /* next might be inside an aloop -- clear stack */
	    CLEAR_ALOOP_STACK() ;
	    cdp = next_label ;
	    break ;

	 case OL_GL:
	    {
	       char *p ;
	       unsigned len ;

	       if (!(p = FINgets(main_fin, &len)))
	       {
		  if (!end_start)  mawk_exit(0) ;

		  cdp = end_start ;
		  zfree(main_start, main_size) ;
		  main_start = end_start = (INST *) 0 ;
	       }
	       else
	       {
		  set_field0(p, len) ;
		  cdp = restart_label ;
		  rt_nr++ ; rt_fnr++ ;
	       }
	    }
	    break ;

	 /* two kinds of OL_GL is a historical stupidity from working on
	    a machine with very slow floating point emulation */
	 case OL_GL_NR:
	    {
	       char *p ;
	       unsigned len ;

	       if (!(p = FINgets(main_fin, &len)))
	       {
		  if (!end_start)  mawk_exit(0) ;

		  cdp = end_start ;
		  zfree(main_start, main_size) ;
		  main_start = end_start = (INST *) 0 ;
	       }
	       else
	       {
		  set_field0(p, len) ;
		  cdp = restart_label ;

		  if (TEST2(NR) != TWO_DOUBLES)	 cast2_to_d(NR) ;

		  NR->dval += 1.0 ; rt_nr++ ;
		  FNR->dval += 1.0 ; rt_fnr++ ;
	       }
	    }
	    break ;


	 case _RANGE:
/* test a range pattern:  pat1, pat2 { action }
   entry :
       cdp[0].op -- a flag, test pat1 if on else pat2
       cdp[1].op -- offset of pat2 code from cdp
       cdp[2].op -- offset of action code from cdp
       cdp[3].op -- offset of code after the action from cdp
       cdp[4] -- start of pat1 code
*/

#define FLAG	cdp[0].op
#define PAT2	cdp[1].op
#define ACTION	  cdp[2].op
#define FOLLOW	  cdp[3].op
#define PAT1	  4

	    if (FLAG)		/* test again pat1 */
	    {
	       execute(cdp + PAT1, sp, fp) ;
	       t = test(sp + 1) ;
	       cell_destroy(sp + 1) ;
	       if (t)  FLAG = 0 ;
	       else
	       {
		  cdp += FOLLOW ;
		  break ;	 /* break the switch */
	       }
	    }

	    /* test against pat2 and then perform the action */
	    execute(cdp + PAT2, sp, fp) ;
	    FLAG = test(sp + 1) ;
	    cell_destroy(sp + 1) ;
	    cdp += ACTION ;
	    break ;

/* function calls  */

	 case _RET0:
	    inc_sp() ;
	    sp->type = C_NOINIT ;
	    /* fall thru */

	 case _RET:

#ifdef	DEBUG
	    if (sp != entry_sp + 1)  bozo("ret") ;
#endif
	    if (old_stack_base) /* reset stack */
	    {
	       /* move the return value */
	       cellcpy(old_sp + 1, sp) ;
	       cell_destroy(sp) ;
	       zfree(stack_base, sizeof(CELL) * EVAL_STACK_SIZE) ;
	       stack_base = old_stack_base ;
	       stack_danger = old_stack_base + DANGER ;
	    }

	    /* return might be inside an aloop -- clear stack */
	    CLEAR_ALOOP_STACK() ;

	    return ;

	 case _CALL:
	    
	    /*  cdp[0] holds ptr to "function block"
		cdp[1] holds number of input arguments
	    */

	    {
	       FBLOCK *fbp = (FBLOCK *) cdp++->ptr ;
	       int a_args = cdp++->op ;	 /* actual number of args */
	       CELL *nfp = sp - a_args + 1 ;	 /* new fp for callee */
	       CELL *local_p = sp + 1 ;	 /* first local argument on stack */
	       char *type_p ;	 /* pts to type of an argument */

	       if (fbp->nargs)	type_p = fbp->typev + a_args - 1 ;

	       /* create space for locals */
	       t = fbp->nargs - a_args ; /* t is number of locals */
	       while (t>0)
	       {
		  t-- ; sp++ ; type_p++ ;
		  sp->type = C_NOINIT ;
		  if (*type_p == ST_LOCAL_ARRAY)
		     sp->ptr = (PTR) new_ARRAY() ;
	       }

	       execute(fbp->code, sp, nfp) ;

	       /* cleanup the callee's arguments */
	       /* putting return value at top of eval stack */
	       if (sp >= nfp)
	       {
		  cp = sp + 1 ;	 /* cp -> the function return */

		  do
		  {
		     if (*type_p == ST_LOCAL_ARRAY)
		     {
			if (sp >= local_p)  
			{
			   array_clear(sp->ptr) ;
			   ZFREE((ARRAY)sp->ptr) ;
			}
		     }
		     else  cell_destroy(sp) ;

		     type_p-- ; sp-- ;

		  }
		  while (sp >= nfp);

		  cellcpy(++sp, cp) ;
		  cell_destroy(cp) ;
	       }
	       else  sp++ ;	    /* no arguments passed */
	    }
	    break ;

	 default:
	    bozo("bad opcode") ;
      }
}


/*
  return 0 if a numeric is zero else return non-zero
  return 0 if a string is "" else return non-zero
*/
int
test(cp)
   register CELL *cp ;
{
 reswitch:

   switch (cp->type)
   {
      case C_NOINIT:
	 return 0 ;
      case C_STRNUM:		/* test as a number */
      case C_DOUBLE:
	 return cp->dval != 0.0 ;
      case C_STRING:
	 return string(cp)->len ;
	 case C_MBSTRN :  check_strnum(cp) ; goto reswitch ;
      default:
	 bozo("bad cell type in call to test") ;
   }
   return 0 ;			 /*can't get here: shutup */
}

/* compare cells at cp and cp+1 and
   frees STRINGs at those cells
*/
static int
compare(cp)
   register CELL *cp ;
{
   int k ;

 reswitch:

   switch (TEST2(cp))
   {
      case TWO_NOINITS:
	 return 0 ;

      case TWO_DOUBLES:
       two_d:
	 return cp->dval > (cp + 1)->dval ? 1 :
	    cp->dval < (cp + 1)->dval ? -1 : 0 ;

      case TWO_STRINGS:
      case STRING_AND_STRNUM:
       two_s:
	 k = strcmp(string(cp)->str, string(cp + 1)->str) ;
	 free_STRING(string(cp)) ;
	 free_STRING(string(cp + 1)) ;
	 return k ;

      case NOINIT_AND_DOUBLE:
      case NOINIT_AND_STRNUM:
      case DOUBLE_AND_STRNUM:
      case TWO_STRNUMS:
	 cast2_to_d(cp) ; goto two_d ;
      case NOINIT_AND_STRING:
      case DOUBLE_AND_STRING:
	 cast2_to_s(cp) ; goto two_s ;
      case TWO_MBSTRNS:
	 check_strnum(cp) ; check_strnum(cp+1) ;
	 goto reswitch ;

      case NOINIT_AND_MBSTRN:
      case DOUBLE_AND_MBSTRN:
      case STRING_AND_MBSTRN:
      case STRNUM_AND_MBSTRN:
	 check_strnum(cp->type == C_MBSTRN ? cp : cp + 1) ;
	 goto reswitch ;

      default:			/* there are no default cases */
	 bozo("bad cell type passed to compare") ;
   }
   return 0 ;			 /* shut up */
}

/* does not assume target was a cell, if so
   then caller should have made a previous
   call to cell_destroy	 */

CELL *
cellcpy(target, source)
   register CELL *target, *source ;
{
   switch (target->type = source->type)
   {
      case C_NOINIT:
      case C_SPACE:
      case C_SNULL:
	 break ;

      case C_DOUBLE:
	 target->dval = source->dval ;
	 break ;

      case C_STRNUM:
	 target->dval = source->dval ;
	 /* fall thru */

      case C_REPL:
      case C_MBSTRN:
      case C_STRING:
	 string(source)->ref_cnt++ ;
	 /* fall thru */

      case C_RE:
	 target->ptr = source->ptr ;
	 break ;

      case C_REPLV:
	 replv_cpy(target, source) ;
	 break ;

      default:
	 bozo("bad cell passed to cellcpy()") ;
	 break ;
   }
   return target ;
}

#ifdef	 DEBUG

void
DB_cell_destroy(cp)		/* HANGOVER time */
   register CELL *cp ;
{
   switch (cp->type)
   {
      case C_NOINIT:
      case C_DOUBLE:
	 break ;

      case C_MBSTRN:
      case C_STRING:
      case C_STRNUM:
	 if (--string(cp)->ref_cnt == 0)
	    zfree(string(cp), string(cp)->len + STRING_OH) ;
	 break ;

      case C_RE:
	 bozo("cell destroy called on RE cell") ;
      default:
	 bozo("cell destroy called on bad cell type") ;
   }
}

#endif



/* convert a double d to a field index	$d -> $i */
static int
d_to_index(d)
   double d;
{

   if (d > MAX_FIELD)
      rt_overflow("maximum number of fields", MAX_FIELD) ;

   if (d >= 0.0)  return (int) d ;

   /* might include nan */
   rt_error("negative field index $%.6g", d) ;
   return 0 ;			 /* shutup */
}