gram.exec

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· EXEC 代码 · 共 222 行

 /* "@(#)gram.exec	4.1	(ULTRIX)	7/17/90" */ 
/************************************************************************
 *									*
 *			Copyright (c) 1984 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/*	@(#)gram.exec	4.3 (Berkeley) 8/7/84	*/
/*
 * gram.exec
 *
 * Grammar for executable statements, f77 compiler pass 1, 4.2 BSD.
 *
 * University of Utah CS Dept modification history:
 *
 * $Log:	gram.exec,v $
 * Revision 3.1  84/10/13  00:36:41  donn
 * Installed Jerry Berkman's version; preserved comment header.
 * 
 * Revision 1.3  84/08/06  18:38:43  donn
 * Fixed a bug in Jerry Berkman's label fixes which caused the same label to
 * be generated twice for some types of logical IF statements.
 * 
 * Revision 1.2  84/08/04  21:09:57  donn
 * Added fixes from Jerry Berkman to allow proper ASSIGNS from format
 * statement numbers.
 * 
 */

exec:	  iffable
	| SDO end_spec intonlyon label intonlyoff opt_comma dospec
		{
		if( !do_name_err ) {
		   if($4->labdefined)
			execerr("no backward DO loops", CNULL);
		   $4->blklevel = blklevel+1;
		   exdo($4->labelno, $7);
		   }
		}
	| logif iffable
		{ exendif();  thiswasbranch = NO; }
	| logif STHEN
	| SELSEIF end_spec SLPAR expr SRPAR STHEN
		{ exelif($4); lastwasbranch = NO; }
	| SELSE end_spec
		{ exelse(); lastwasbranch = NO; }
	| SENDIF end_spec
		{ exendif(); lastwasbranch = NO; }
	;

logif:	  SLOGIF end_spec SLPAR expr SRPAR
		{ exif($4); }
	;

dospec:	  name SEQUALS exprlist
		{ if( $1->vclass != CLPARAM ) {
			$$ = mkchain($1, $3);
			do_name_err = 0;
		  } else {
			err("symbolic constant not allowed as DO variable");
		 	do_name_err = 1;
		  }
		}
	;

iffable:  let lhs SEQUALS expr
		{ exequals($2, $4); }
	| SASSIGN end_spec assignlabel STO name
		{ if( $5->vclass != CLPARAM ) {
			exassign($5, $3);
		  } else {
			err("can only assign to a variable");
		  }
		}
	| SCONTINUE end_spec
	| goto
	| io
		{ inioctl = NO; }
	| SARITHIF end_spec SLPAR expr SRPAR label SCOMMA label SCOMMA label
		{ exarif($4, $6, $8, $10);  thiswasbranch = YES; }
	| call
		{ excall($1, PNULL, 0, labarray); }
	| call SLPAR SRPAR
		{ excall($1, PNULL, 0, labarray); }
	| call SLPAR callarglist SRPAR
		{ if(nstars < MAXLABLIST)
			excall($1, mklist($3), nstars, labarray);
		  else
			err("too many alternate returns");
		}
	| SRETURN end_spec opt_expr
		{ exreturn($3);  thiswasbranch = YES; }
	| stop end_spec opt_expr
		{ exstop($1, $3);  thiswasbranch = $1; }
	;

assignlabel:   SICON
		{ $$ = mklabel( convci(toklen, token) ); }
	;

let:	  SLET
		{ if(parstate == OUTSIDE)
			{
			newproc();
			startproc(PNULL, CLMAIN);
			}
		  if( yystno != 0 && thislabel->labtype != LABFORMAT)
			if (optimflag)
				optbuff (SKLABEL, 0, thislabel->labelno, 1);
			else
				putlabel(thislabel->labelno);
		}
	;

goto:	  SGOTO end_spec label
		{ exgoto($3);  thiswasbranch = YES; }
	| SASGOTO end_spec name
		{ if( $3->vclass != CLPARAM ) {
			exasgoto($3);  thiswasbranch = YES;
		  } else {
			err("must go to label or assigned variable");
		  }
		}
	| SASGOTO end_spec name opt_comma SLPAR labellist SRPAR
		{ if( $3->vclass != CLPARAM ) {
			exasgoto($3);  thiswasbranch = YES;
		  } else {
			err("must go to label or assigned variable");
		  }
		}
	| SCOMPGOTO end_spec SLPAR labellist SRPAR opt_comma expr
		{ if(nstars < MAXLABLIST)
			if (optimflag)
			    optbuff (SKCMGOTO, fixtype($7), nstars, labarray);
			else
			    putcmgo (fixtype($7), nstars, labarray);
		  else
			err("computed GOTO list too long");
		}
	;

opt_comma:
	| SCOMMA
	;

call:	  SCALL end_spec name
		{ nstars = 0; $$ = $3; }
	;

callarglist:  callarg
		{ $$ = ($1 ? mkchain($1,CHNULL) : CHNULL); }
	| callarglist SCOMMA callarg
		{ if($3)
			if($1) $$ = hookup($1, mkchain($3,CHNULL));
			else $$ = mkchain($3,CHNULL);
		  else
			$$ = $1;
		}
	;

callarg:  expr
	| SSTAR label
		{ if(nstars<MAXLABLIST) labarray[nstars++] = $2; $$ = 0; }
	;

stop:	  SPAUSE
		{ $$ = 0; }
	| SSTOP
		{ $$ = 1; }
	;

exprlist:  expr
		{ $$ = mkchain($1, CHNULL); }
	| exprlist SCOMMA expr
		{ $$ = hookup($1, mkchain($3,CHNULL) ); }
	;

end_spec:
		{ if(parstate == OUTSIDE)
			{
			newproc();
			startproc(PNULL, CLMAIN);
			}
		  if(parstate < INDATA) enddcl();
		  if( yystno != 0 && thislabel->labtype != LABFORMAT)
			if (optimflag)
				optbuff (SKLABEL, 0, thislabel->labelno, 1);
			else
				putlabel(thislabel->labelno);
		  yystno = 0;
		}
	;

intonlyon:
		{ intonly = YES; }
	;

intonlyoff:
		{ intonly = NO; }
	;