cgram.y

unix v7是最后一个广泛发布的研究型UNIX版本

%term NAME  2
%term STRING  3
%term ICON  4
%term FCON  5
%term PLUS   6
%term MINUS   8
%term MUL   11
%term AND   14
%term OR   17
%term ER   19
%term QUEST  21
%term COLON  22
%term ANDAND  23
%term OROR  24

/*	special interfaces for yacc alone */
/*	These serve as abbreviations of 2 or more ops:
	ASOP	=, = ops
	RELOP	LE,LT,GE,GT
	EQUOP	EQ,NE
	DIVOP	DIV,MOD
	SHIFTOP	LS,RS
	ICOP	ICR,DECR
	UNOP	NOT,COMPL
	STROP	DOT,STREF

	*/
%term ASOP  25
%term RELOP  26
%term EQUOP  27
%term DIVOP  28
%term SHIFTOP  29
%term INCOP  30
%term UNOP  31
%term STROP  32

/*	reserved words, etc */
%term TYPE  33
%term CLASS  34
%term STRUCT  35
%term RETURN  36
%term GOTO  37
%term IF  38
%term ELSE  39
%term SWITCH  40
%term BREAK  41
%term CONTINUE  42
%term WHILE  43
%term DO  44
%term FOR  45
%term DEFAULT  46
%term CASE  47
%term SIZEOF  48
%term ENUM 49


/*	little symbols, etc. */
/*	namely,

	LP	(
	RP	)

	LC	{
	RC	}

	LB	[
	RB	]

	CM	,
	SM	;

	*/

%term LP  50
%term RP  51
%term LC  52
%term RC  53
%term LB  54
%term RB  55
%term CM  56
%term SM  57
%term ASSIGN  58

/* at last count, there were 7 shift/reduce, 1 reduce/reduce conflicts
/* these involved:
	if/else
	recognizing functions in various contexts, including declarations
	error recovery
	*/

%left CM
%right ASOP ASSIGN
%right QUEST COLON
%left OROR
%left ANDAND
%left OR
%left ER
%left AND
%left EQUOP
%left RELOP
%left SHIFTOP
%left PLUS MINUS
%left MUL DIVOP
%right UNOP
%right INCOP SIZEOF
%left LB LP STROP
%{
# include "mfile1"
%}

	/* define types */
%start ext_def_list

%type <intval> con_e ifelprefix ifprefix whprefix forprefix doprefix switchpart
		enum_head str_head name_lp
%type <nodep> e .e term attributes oattributes type enum_dcl struct_dcl
		cast_type null_decl funct_idn declarator fdeclarator nfdeclarator
		elist

%token <intval> CLASS NAME STRUCT RELOP CM DIVOP PLUS MINUS SHIFTOP MUL AND OR ER ANDAND OROR
		ASSIGN STROP INCOP UNOP ICON
%token <nodep> TYPE

%%

%{
	static int fake = 0;
	static char fakename[NCHNAM+1];
%}

ext_def_list:	   ext_def_list external_def
		|
			=ftnend();
		;
external_def:	   data_def
			={ curclass = SNULL;  blevel = 0; }
		|  error
			={ curclass = SNULL;  blevel = 0; }
		;
data_def:
		   oattributes  SM
			={  $1->op = FREE; }
		|  oattributes init_dcl_list  SM
			={  $1->op = FREE; }
		|  oattributes fdeclarator {
				defid( tymerge($1,$2), curclass==STATIC?STATIC:EXTDEF );
				}  function_body
			={  
			    if( blevel ) cerror( "function level error" );
			    if( reached ) retstat |= NRETVAL; 
			    $1->op = FREE;
			    ftnend();
			    }
		;

function_body:	   arg_dcl_list compoundstmt
		;
arg_dcl_list:	   arg_dcl_list declaration
		| 	={  blevel = 1; }
		;

stmt_list:	   stmt_list statement
		|  /* empty */
			={  bccode();
			    locctr(PROG);
			    }
		;

dcl_stat_list	:  dcl_stat_list attributes SM
			={  $2->op = FREE; }
		|  dcl_stat_list attributes init_dcl_list SM
			={  $2->op = FREE; }
		|  /* empty */
		;
declaration:	   attributes declarator_list  SM
			={ curclass = SNULL;  $1->op = FREE; }
		|  attributes SM
			={ curclass = SNULL;  $1->op = FREE; }
		|  error  SM
			={  curclass = SNULL; }
		;
oattributes:	  attributes
		|  /* VOID */
			={  $$ = mkty(INT,0,INT);  curclass = SNULL; }
		;
attributes:	   class type
			={  $$ = $2; }
		|  type class
		|  class
			={  $$ = mkty(INT,0,INT); }
		|  type
			={ curclass = SNULL ; }
		;


class:		  CLASS
			={  curclass = $1; }
		;

type:		   TYPE
		|  TYPE TYPE
			={  $1->type = types( $1->type, $2->type, UNDEF );
			    $2->op = FREE;
			    }
		|  TYPE TYPE TYPE
			={  $1->type = types( $1->type, $2->type, $3->type );
			    $2->op = $3->op = FREE;
			    }
		|  struct_dcl
		|  enum_dcl
		;

enum_dcl:	   enum_head LC moe_list optcomma RC
			={ $$ = dclstruct($1); }
		|  ENUM NAME
			={  $$ = rstruct($2,0);  stwart = instruct; }
		;

enum_head:	   ENUM
			={  $$ = bstruct(-1,0); }
		|  ENUM NAME
			={  $$ = bstruct($2,0); }
		;

moe_list:	   moe
		|  moe_list CM moe
		;

moe:		   NAME
			={  moedef( $1 ); }
		|  NAME ASSIGN con_e
			={  strucoff = $3;  moedef( $1 ); }
		;

struct_dcl:	   str_head LC type_dcl_list optsemi RC
			={ $$ = dclstruct($1);  }
		|  STRUCT NAME
			={  $$ = rstruct($2,$1); }
		;

str_head:	   STRUCT
			={  $$ = bstruct(-1,$1);  stwart=0; }
		|  STRUCT NAME
			={  $$ = bstruct($2,$1);  stwart=0;  }
		;

type_dcl_list:	   type_declaration
		|  type_dcl_list SM type_declaration
		;

type_declaration:  type declarator_list
			={ curclass = SNULL;  stwart=0; $1->op = FREE; }
		|  type
			={  if( curclass != MOU ){
				curclass = SNULL;
				}
			    else {
				sprintf( fakename, "$%dFAKE", fake++ );
				defid( tymerge($1, bdty(NAME,NIL,lookup( fakename, SMOS ))), curclass );
				}
			    stwart = 0;
			    $1->op = FREE;
			    }
		;


declarator_list:   declarator
			={ defid( tymerge($<nodep>0,$1), curclass);  stwart = instruct; }
		|  declarator_list  CM {$<nodep>$=$<nodep>0;}  declarator
			={ defid( tymerge($<nodep>0,$4), curclass);  stwart = instruct; }
		;
declarator:	   fdeclarator
		|  nfdeclarator
		|  nfdeclarator COLON con_e
			%prec CM
			={  if( !(instruct&INSTRUCT) ) uerror( "field outside of structure" );
			    if( $3<0 || $3 >= FIELD ){
				uerror( "illegal field size" );
				$3 = 1;
				}
			    defid( tymerge($<nodep>0,$1), FIELD|$3 );
			    $$ = NIL;
			    }
		|  COLON con_e
			%prec CM
			={  if( !(instruct&INSTRUCT) ) uerror( "field outside of structure" );
			    falloc( stab, $2, -1, $<nodep>0 );  /* alignment or hole */
			    $$ = NIL;
			    }
		|  error
			={  $$ = NIL; }
		;

		/* int (a)();   is not a function --- sorry! */
nfdeclarator:	   MUL nfdeclarator		
			={  umul:
				$$ = bdty( UNARY MUL, $2, 0 ); }
		|  nfdeclarator  LP   RP		
			={  uftn:
				$$ = bdty( UNARY CALL, $1, 0 );  }
		|  nfdeclarator LB RB		
			={  uary:
				$$ = bdty( LB, $1, 0 );  }
		|  nfdeclarator LB con_e RB	
			={  bary:
				if( (int)$3 <= 0 ) werror( "zero or negative subscript" );
				$$ = bdty( LB, $1, $3 );  }
		|  NAME  		
			={  $$ = bdty( NAME, NIL, $1 );  }
		|   LP  nfdeclarator  RP 		
			={ $$=$2; }
		;
fdeclarator:	   MUL fdeclarator
			={  goto umul; }
		|  fdeclarator  LP   RP
			={  goto uftn; }
		|  fdeclarator LB RB
			={  goto uary; }
		|  fdeclarator LB con_e RB
			={  goto bary; }
		|   LP  fdeclarator  RP
			={ $$ = $2; }
		|  name_lp  name_list  RP
			={
				if( blevel!=0 ) uerror("function declaration in bad context");
				$$ = bdty( UNARY CALL, bdty(NAME,NIL,$1), 0 );
				stwart = 0;
				}
		|  name_lp RP
			={
				$$ = bdty( UNARY CALL, bdty(NAME,NIL,$1), 0 );
				stwart = 0;
				}
		;

name_lp:	  NAME LP
			={
				/* turn off typedefs for argument names */
				stwart = SEENAME;
				}
		;

name_list:	   NAME			
			={ ftnarg( $1 );  stwart = SEENAME; }
		|  name_list  CM  NAME 
			={ ftnarg( $3 );  stwart = SEENAME; }
		;
		/* always preceeded by attributes: thus the $<nodep>0's */
init_dcl_list:	   init_declarator
			%prec CM
		|  init_dcl_list  CM {$<nodep>$=$<nodep>0;}  init_declarator
		;
		/* always preceeded by attributes */
xnfdeclarator:	   nfdeclarator
			={  defid( $1 = tymerge($<nodep>0,$1), curclass);
			    beginit($1->rval);
			    }
		|  error
		;
		/* always preceeded by attributes */
init_declarator:   nfdeclarator
			={  nidcl( tymerge($<nodep>0,$1) ); }
		|  fdeclarator
			={  defid( tymerge($<nodep>0,$1), uclass(curclass) );
			}
		|  xnfdeclarator optasgn e
			%prec CM
			={  doinit( $3 );
			    endinit(); }
		|  xnfdeclarator optasgn LC init_list optcomma RC
			={  endinit(); }
		;

init_list:	   initializer
			%prec CM
		|  init_list  CM  initializer
		;
initializer:	   e
			%prec CM
			={  doinit( $1 ); }
		|  ibrace init_list optcomma RC
			={  irbrace(); }
		;

optcomma	:	/* VOID */
		|  CM
		;

optsemi		:	/* VOID */
		|  SM
		;

optasgn		:	/* VOID */
			={  werror( "old-fashioned initialization: use =" ); }
		|  ASSIGN
		;

ibrace		: LC
			={  ilbrace(); }
		;

/*	STATEMENTS	*/

compoundstmt:	   begin dcl_stat_list stmt_list RC
			={  --blevel;
			    if( blevel == 1 ) blevel = 0;
			    clearst( blevel );
			    checkst( blevel );
			    autooff = *--psavbc;
			    regvar = *--psavbc;
			    }
		;

begin:		  LC
			={  if( blevel == 1 ) dclargs();
			    ++blevel;
			    if( psavbc > &asavbc[BCSZ-2] ) cerror( "nesting too deep" );
			    *psavbc++ = regvar;
			    *psavbc++ = autooff;
			    }
		;

statement:	   e   SM
			={ ecomp( $1 ); }
		|  compoundstmt
		|  ifprefix statement
			={ deflab($1);
			   reached = 1;
			   }
		|  ifelprefix statement
			={  if( $1 != NOLAB ){
				deflab( $1 );
				reached = 1;
				}
			    }
		|  whprefix statement
			={  branch(  contlab );
			    deflab( brklab );
			    if( (flostat&FBRK) || !(flostat&FLOOP)) reached = 1;
			    else reached = 0;
			    resetbc(0);
			    }
		|  doprefix statement WHILE  LP  e  RP   SM
			={  deflab( contlab );
			    if( flostat & FCONT ) reached = 1;
			    ecomp( buildtree( CBRANCH, buildtree( NOT, $5, NIL ), bcon( $1 ) ) );
			    deflab( brklab );
			    reached = 1;
			    resetbc(0);
			    }
		|  forprefix .e RP statement
			={  deflab( contlab );
			    if( flostat&FCONT ) reached = 1;
			    if( $2 ) ecomp( $2 );
			    branch( $1 );
			    deflab( brklab );
			    if( (flostat&FBRK) || !(flostat&FLOOP) ) reached = 1;
			    else reached = 0;
			    resetbc(0);
			    }
		| switchpart statement
			={  if( reached ) branch( brklab );
			    deflab( $1 );