[qfcc] Add support for named labels in statements

Yeah, I've finally decided to implement goto. Limited to function scope
of course.

tools/qfcc/include/expr.h

@@ -290,6 +290,19 @@ const char *new_label_name (void);
 */
 expr_t *new_label_expr (void);
 
+/**	Create a named label expression node.
+
+	The label name is set using new_label_name(), but the symbol is used to add
+	the label to the function's label scope symbol table. If the label already
+	exists in the function's label scope, then the existing label is returned,
+	allowing for forward label declarations.
+
+	\param label	The name symbol to use for adding the label to the function
+					label scope.
+	\return			The new label expression (::ex_label_t) node.
+*/
+expr_t *named_label_expr (struct symbol_s *label);
+
 /**	Create a new label reference expression node.
 
 	Used for taking the address of a label (eg. jump tables).

tools/qfcc/include/function.h

@@ -79,6 +79,7 @@ typedef struct function_s {
 		scope symbol table's defspace.
 	*/
 	struct symtab_s    *symtab;
+	struct symtab_s    *label_scope;
 	struct reloc_s     *refs;		///< relocation targets for this function
 	struct expr_s      *var_init;
 	const char         *name;		///< nice name for __PRETTY_FUNCTION__

tools/qfcc/source/expr.c

@@ -495,6 +495,27 @@ new_label_expr (void)
 	return l;
 }
 
+expr_t *
+named_label_expr (symbol_t *label)
+{
+	symbol_t   *sym;
+
+	if (!current_func) {
+		// XXX this might be only an error
+		internal_error (0, "label defined outside of function scope");
+	}
+
+	sym = symtab_lookup (current_func->label_scope, label->name);
+
+	if (sym) {
+		return sym->s.expr;
+	}
+	label->sy_type = sy_expr;
+	label->s.expr = new_label_expr ();
+	symtab_addsymbol (current_func->label_scope, label);
+	return label->s.expr;
+}
+
 expr_t *
 new_label_ref (ex_label_t *label)
 {

tools/qfcc/source/function.c

@@ -493,6 +493,7 @@ build_scope (symbol_t *fsym, symtab_t *parent)
 
 	symtab = new_symtab (parent, stab_local);
 	fsym->s.func->symtab = symtab;
+	fsym->s.func->label_scope = new_symtab (0, stab_local);
 	symtab->space = defspace_new (ds_virtual);
 	current_symtab = symtab;
 

tools/qfcc/source/qc-parse.y

@@ -188,7 +188,7 @@ int yylex (void);
 %type	<expr>		unary_expr ident_expr cast_expr opt_arg_list arg_list
 %type	<expr>		init_var_decl_list init_var_decl
 %type	<switch_block> switch_block
-%type	<symbol>	identifier
+%type	<symbol>	identifier label
 
 %type	<symbol>	overloaded_identifier
 
@@ -1292,6 +1292,10 @@ statement
 			else
 				error (0, "continue outside of loop");
 		}
+	| label
+		{
+			$$ = named_label_expr ($1);
+		}
 	| CASE expr ':'
 		{
 			$$ = case_label_expr (switch_block, $2);
@@ -1358,6 +1362,10 @@ else
 		}
 	;
 
+label
+	: NAME ':'
+	;
+
 bool_label
 	: /* empty */
 		{