parse.y

gcc库的原代码,对编程有很大帮助.

template_parm:
	/* The following rules introduce a new reduce/reduce
	   conflict on the ',' and '>' input tokens: they are valid
	   prefixes for a `structsp', which means they could match a
	   nameless parameter.  See 14.6, paragraph 3.
	   By putting them before the `parm' rule, we get
	   their match before considering them nameless parameter
	   declarations.  */
	  template_type_parm
		{ $$ = build_tree_list (NULL_TREE, $$); }
	| template_type_parm '=' typespec
		{ $$ = build_tree_list ($3, $$); }
	| full_parm
	;

overloaddef:
	  OVERLOAD ov_identifiers ';'
		{ warning ("use of `overload' is an anachronism"); }
	;

ov_identifiers: IDENTIFIER
		{ declare_overloaded ($1); }
	| ov_identifiers ',' IDENTIFIER
		{ declare_overloaded ($3); }
	;
	  
template_def:
	/* Class template declarations go here; they aren't normal class
	   declarations, because we can't process the bodies yet.  */
	  template_header named_class_head_sans_basetype '{'
		{ yychar = '{'; goto template1; }
	 ';'
	| template_header named_class_head_sans_basetype_defn '{'
		{ yychar = '{'; goto template1; }
	 ';'
	| template_header named_class_head_sans_basetype ':'
		{ yychar = ':'; goto template1; }
	 ';'
	| template_header named_class_head_sans_basetype_defn ':'
		{
		  yychar = ':';
		template1:
		  if (current_aggr == signature_type_node)
		    sorry ("template type defining a signature");
		  /* Maybe pedantic warning for union?
		     How about an enum? :-)  */
		  end_template_decl ($1, $2, current_aggr, 1);
		  reinit_parse_for_template (yychar, $1, $2);
		  yychar = YYEMPTY;
		}
	  ';'
	| template_header named_class_head_sans_basetype ';'
		{
		  end_template_decl ($1, $2, current_aggr, 0);
		  /* declare $2 as template name with $1 parm list */
		}
	| template_header named_class_head_sans_basetype_defn ';'
		{
		  end_template_decl ($1, $2, current_aggr, 0);
		  /* declare $2 as template name with $1 parm list */
		}
	| template_header /* notype_initdcl0 ';' */
	  notype_declarator exception_specification_opt maybeasm maybe_attribute
	  fn_tmpl_end
		{
		  tree d;
		  int momentary;
		  int def = ($6 != ';');
		  momentary = suspend_momentary ();
		  d = start_decl ($<ttype>2, /*current_declspecs*/NULL_TREE, 0,
				  $3);
		  cplus_decl_attributes (d, $5, /*prefix_attributes*/NULL_TREE);
		  cp_finish_decl (d, NULL_TREE, $4, 0, 0);
		  end_template_decl ($1, d, 0, def);
		  if (def)
		    reinit_parse_for_template ((int) $6, $1, d);
		  resume_momentary (momentary);
		}
	| template_header typed_declspecs /*initdcl0*/
	  declarator exception_specification_opt maybeasm maybe_attribute
	  fn_tmpl_end
		{
		  tree d, specs, attrs;
		  int momentary;
		  int def = ($7 != ';');
		  split_specs_attrs ($2, &specs, &attrs);
		  momentary = suspend_momentary ();
		  d = start_decl ($<ttype>3, specs, 0, $<ttype>4);
		  cplus_decl_attributes (d, $6, attrs);
		  cp_finish_decl (d, NULL_TREE, $5, 0, 0);
		  end_template_decl ($1, d, 0, def);
		  if (def)
		    {
		      reinit_parse_for_template ((int) $7, $1, d);
		      yychar = YYEMPTY;
		    }
		  note_list_got_semicolon ($<ttype>2);
		  resume_momentary (momentary);
		}
	| template_header declmods notype_declarator fn_tmpl_end
		{
		  tree d, specs, attrs;
		  int def = ($4 != ';');
		  split_specs_attrs ($2, &specs, &attrs);
		  d = start_decl ($<ttype>3, specs, 0, NULL_TREE);
		  cplus_decl_attributes (d, NULL_TREE, attrs);
		  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
		  end_template_decl ($1, d, 0, def);
		  if (def)
		    reinit_parse_for_template ((int) $4, $1, d);
		}
	/* Try to recover from syntax errors in templates.  */
	| template_header error '}'	{ end_template_decl ($1, 0, 0, 0); }
	| template_header error ';'	{ end_template_decl ($1, 0, 0, 0); }
	;

fn_tmpl_end: '{'		{ $$ = '{'; }
	| ':'			{ $$ = ':'; }
	| ';'			{ $$ = ';'; }
	| '='			{ $$ = '='; }
	| RETURN		{ $$ = RETURN; }
	;

datadef:
	  nomods_initdecls ';'
		{}
	| declmods notype_initdecls ';'
		{}
	/* Normal case to make fast: "const i;".  */
	| declmods notype_declarator ';'
		{ tree d, specs, attrs;
		  split_specs_attrs ($1, &specs, &attrs);
		  d = start_decl ($<ttype>2, specs, 0, NULL_TREE);
		  cplus_decl_attributes (d, NULL_TREE, attrs);
		  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
		}
	| typed_declspecs initdecls ';'
		{
		  note_list_got_semicolon ($<ttype>$);
		}
	/* Normal case: make this fast.  */
	| typed_declspecs declarator ';'
		{ tree d, specs, attrs;
		  split_specs_attrs ($1, &specs, &attrs);
		  d = start_decl ($<ttype>2, specs, 0, NULL_TREE);
		  cplus_decl_attributes (d, NULL_TREE, attrs);
		  cp_finish_decl (d, NULL_TREE, NULL_TREE, 0, 0);
		  note_list_got_semicolon ($<ttype>$);
		}
        | declmods ';'
	  { pedwarn ("empty declaration"); }
	| explicit_instantiation ';'
	| typed_declspecs ';'
	  {
	    tree t, attrs;
	    split_specs_attrs ($1, &t, &attrs);
	    shadow_tag (t);
	    if (TREE_CODE (t) == TREE_LIST
		&& TREE_PURPOSE (t) == NULL_TREE)
	      {
		t = TREE_VALUE (t);
		if (IS_AGGR_TYPE (t)
		    && IDENTIFIER_TEMPLATE (TYPE_IDENTIFIER (t)))
		  {
		    if (CLASSTYPE_USE_TEMPLATE (t) == 0)
		      SET_CLASSTYPE_TEMPLATE_SPECIALIZATION (t);
		    else if (CLASSTYPE_TEMPLATE_INSTANTIATION (t))
		      error ("override declaration for already-expanded template");
		  }
	      }
	    note_list_got_semicolon ($<ttype>$);
	  }
	| error ';'
	| error '}'
	| ';'
	;

ctor_initializer_opt:
	  nodecls
		{ $$ = 0; }
	| base_init
		{ $$ = 1; }
	;

maybe_return_init:
	  /* empty */
	| return_init
	| return_init ';'
	;

eat_saved_input:
	  /* empty */
	| END_OF_SAVED_INPUT
	;

fndef:
	  fn.def1 maybe_return_init ctor_initializer_opt compstmt_or_error
		{
		  finish_function (lineno, (int)$3, 0);
		  if ($<ttype>$) process_next_inline ($<ttype>$);
		}
	| fn.def1 maybe_return_init function_try_block
		{
		  if ($<ttype>$) process_next_inline ($<ttype>$);
		}
	  eat_saved_input
	| typed_declspecs declarator error
		{}
	| declmods notype_declarator error
		{}
	| notype_declarator error
		{}
	;

fn.def1:
	  typed_declspecs declarator exception_specification_opt
		{ tree specs, attrs;
		  split_specs_attrs ($1, &specs, &attrs);
		  if (! start_function (specs, $2, $3, attrs, 0))
		    YYERROR1;
		  reinit_parse_for_function ();
		  $$ = NULL_TREE; }
	| declmods notype_declarator exception_specification_opt
		{ tree specs = strip_attrs ($1);
		  if (! start_function (specs, $2, $3, NULL_TREE, 0))
		    YYERROR1;
		  reinit_parse_for_function ();
		  $$ = NULL_TREE; }
	| notype_declarator exception_specification_opt
		{ if (! start_function (NULL_TREE, $$, $2, NULL_TREE, 0))
		    YYERROR1;
		  reinit_parse_for_function ();
		  $$ = NULL_TREE; }
	| PRE_PARSED_FUNCTION_DECL
		{ start_function (NULL_TREE, TREE_VALUE ($$),
				  NULL_TREE, NULL_TREE, 1);
		  reinit_parse_for_function (); }
	;

/* more C++ complexity.  See component_decl for a comment on the
   reduce/reduce conflict introduced by these rules.  */
fn.def2:
	  typed_declspecs '(' parmlist ')' type_quals exception_specification_opt
		{ tree specs = strip_attrs ($1);
		  $$ = build_parse_node (CALL_EXPR, TREE_VALUE (specs), $3, $5);
		  $$ = start_method (TREE_CHAIN (specs), $$, $6);
		 rest_of_mdef:
		  if (! $$)
		    YYERROR1;
		  if (yychar == YYEMPTY)
		    yychar = YYLEX;
		  reinit_parse_for_method (yychar, $$); }
	| typed_declspecs LEFT_RIGHT type_quals exception_specification_opt
		{ tree specs = strip_attrs ($1);
		  $$ = build_parse_node (CALL_EXPR, TREE_VALUE (specs),
					 empty_parms (), $3);
		  $$ = start_method (TREE_CHAIN (specs), $$, $4);
		  goto rest_of_mdef;
		}
	| typed_declspecs declarator exception_specification_opt
		{ tree specs = strip_attrs ($1);
		  $$ = start_method (specs, $2, $3); goto rest_of_mdef; }
	| declmods notype_declarator exception_specification_opt
		{ tree specs = strip_attrs ($1);
		  $$ = start_method (specs, $2, $3); goto rest_of_mdef; }
	| notype_declarator exception_specification_opt
		{ $$ = start_method (NULL_TREE, $$, $2); goto rest_of_mdef; }
	;

return_id: RETURN IDENTIFIER
		{
		  if (! current_function_parms_stored)
		    store_parm_decls ();
		  $$ = $2;
		}
	;

return_init: return_id maybe_init
		{ store_return_init ($<ttype>$, $2); }
	| return_id '(' nonnull_exprlist ')'
		{ store_return_init ($<ttype>$, $3); }
	| return_id LEFT_RIGHT
		{ store_return_init ($<ttype>$, NULL_TREE); }
	;

base_init:
	  ':' .set_base_init member_init_list
		{
		  if ($3 == 0)
		    error ("no base initializers given following ':'");
		  setup_vtbl_ptr ();
		  /* Always keep the BLOCK node associated with the outermost
		     pair of curley braces of a function.  These are needed
		     for correct operation of dwarfout.c.  */
		  keep_next_level ();
		}
	;

.set_base_init:
	/* empty */
		{
		  if (! current_function_parms_stored)
		    store_parm_decls ();

		  if (DECL_CONSTRUCTOR_P (current_function_decl))
		    {
		      /* Make a contour for the initializer list.  */
		      pushlevel (0);
		      clear_last_expr ();
		      expand_start_bindings (0);
		    }
		  else if (current_class_type == NULL_TREE)
		    error ("base initializers not allowed for non-member functions");
		  else if (! DECL_CONSTRUCTOR_P (current_function_decl))
		    error ("only constructors take base initializers");
		}
	;

member_init_list:
	  /* empty */
		{ $$ = 0; }
	| member_init
		{ $$ = 1; }
	| member_init_list ',' member_init
	| member_init_list error
	;

member_init: '(' nonnull_exprlist ')'
		{
		  if (current_class_name && !flag_traditional)
		    pedwarn ("anachronistic old style base class initializer");
		  expand_member_init (C_C_D, NULL_TREE, $2);
		}
	| LEFT_RIGHT
		{
		  if (current_class_name && !flag_traditional)
		    pedwarn ("anachronistic old style base class initializer");
		  expand_member_init (C_C_D, NULL_TREE, void_type_node);
		}
	| notype_identifier '(' nonnull_exprlist ')'
		{ expand_member_init (C_C_D, $<ttype>$, $3); }
	| notype_identifier LEFT_RIGHT
		{ expand_member_init (C_C_D, $<ttype>$, void_type_node); }
	| complete_type_name '(' nonnull_exprlist ')'
		{ expand_member_init (C_C_D, $<ttype>$, $3); }
	| complete_type_name LEFT_RIGHT
		{ expand_member_init (C_C_D, $<ttype>$, void_type_node); }
	/* GNU extension */
	| notype_qualified_id '(' nonnull_exprlist ')'
		{
		  do_member_init (OP0 ($1), OP1 ($1), $3);
		}
	| notype_qualified_id LEFT_RIGHT
		{
		  do_member_init (OP0 ($1), OP1 ($1), void_type_node);
		}
	;

identifier:
	  IDENTIFIER
	| TYPENAME
	| PTYPENAME
	| NSNAME
	;

notype_identifier:
	  IDENTIFIER
	| PTYPENAME 
	| NSNAME %prec EMPTY
	;

identifier_defn:
	  IDENTIFIER_DEFN
	| TYPENAME_DEFN
	| PTYPENAME_DEFN
	;

explicit_instantiation:
	  TEMPLATE specialization template_instantiation
		{ do_type_instantiation ($3 ? $3 : $2, NULL_TREE); }
	| TEMPLATE typed_declspecs declarator
		{ tree specs = strip_attrs ($2);
		  do_function_instantiation (specs, $3, NULL_TREE); }
	| TEMPLATE notype_declarator
		{ do_function_instantiation (NULL_TREE, $2, NULL_TREE); }
	| SCSPEC TEMPLATE specialization template_instantiation
		{ do_type_instantiation ($4 ? $4 : $3, $1); }
	| SCSPEC TEMPLATE typed_declspecs declarator
		{ tree specs = strip_attrs ($3);
		  do_function_instantiation (specs, $4, $1); }
	| SCSPEC TEMPLATE notype_declarator
		{ do_function_instantiation (NULL_TREE, $3, $1); }
	;

template_type:
	  template_type_name tmpl.2 template_instantiation
		{ if ($3) $$ = $3; }
	;

template_type_name:
	  PTYPENAME '<' template_arg_list '>'
		{ $$ = lookup_template_class ($$, $3, NULL_TREE); }
	| PTYPENAME '<' '>'
		{ $$ = lookup_template_class ($$, NULL_TREE, NULL_TREE); }
	| TYPENAME  '<' template_arg_list '>'
		{ $$ = lookup_template_class ($$, $3, NULL_TREE); }
	;

tmpl.2: 
	  /* empty */ %prec EMPTY
		{ $$ = instantiate_class_template ($<ttype>0, 1); }
	;

template_arg_list:
	  template_arg
		{ $$ = build_tree_list (NULL_TREE, $$); }
	| template_arg_list ',' template_arg
		{ $$ = chainon ($$, build_tree_list (NULL_TREE, $3)); }
	;

template_arg:
	  type_id
		{ $$ = groktypename ($$); }
	| expr_no_commas  %prec UNARY
	;

template_instantiate_once:
	  PRE_PARSED_CLASS_DECL maybe_base_class_list
		{
		  tree t, decl, tmpl;

		  tmpl = TREE_PURPOSE (IDENTIFIER_TEMPLATE ($1));
		  t = xref_tag (DECL_TEMPLATE_INFO (tmpl)->aggr, $1, $2, 0);
		  set_current_level_tags_transparency (1);
		  my_friendly_assert (TREE_CODE (t) == RECORD_TYPE
				      || TREE_CODE (t) == UNION_TYPE, 257);
		  $<ttype>$ = t;

		  /* Now, put a copy of the decl in global scope, to avoid
		     recursive expansion.  */