use frozen string of symbols

* range.c (range_step, range_each): String#upto should never
  modifies the receiver, use frozen strings to enumerate symbols.

* re.c (reg_operand): matching target is not modified.

* ext/socket/constants.c (constant_arg): str_to_int never modifies
  argument strings.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50306 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/constants.c

@@ -22,7 +22,7 @@ constant_arg(VALUE arg, int (*str_to_int)(const char*, long, int*), const char *
     int ret;
 
     if (SYMBOL_P(arg)) {
-        arg = rb_sym_to_s(arg);
+        arg = rb_sym2str(arg);
         goto str;
     }
     else if (!NIL_P(tmp = rb_check_string_type(arg))) {

range.c

@@ -429,11 +429,11 @@ range_step(int argc, VALUE *argv, VALUE range)
     else if (SYMBOL_P(b) && SYMBOL_P(e)) { /* symbols are special */
 	VALUE args[2], iter[2];
 
-	args[0] = rb_sym_to_s(e);
+	args[0] = rb_sym2str(e);
 	args[1] = EXCL(range) ? Qtrue : Qfalse;
 	iter[0] = INT2FIX(1);
 	iter[1] = step;
-	rb_block_call(rb_sym_to_s(b), rb_intern("upto"), 2, args, sym_step_i, (VALUE)iter);
+	rb_block_call(rb_sym2str(b), rb_intern("upto"), 2, args, sym_step_i, (VALUE)iter);
     }
     else if (ruby_float_step(b, e, step, EXCL(range))) {
 	/* done */
@@ -771,9 +771,9 @@ range_each(VALUE range)
     else if (SYMBOL_P(beg) && SYMBOL_P(end)) { /* symbols are special */
 	VALUE args[2];
 
-	args[0] = rb_sym_to_s(end);
+	args[0] = rb_sym2str(end);
 	args[1] = EXCL(range) ? Qtrue : Qfalse;
-	rb_block_call(rb_sym_to_s(beg), rb_intern("upto"), 2, args, sym_each_i, 0);
+	rb_block_call(rb_sym2str(beg), rb_intern("upto"), 2, args, sym_each_i, 0);
     }
     else {
 	VALUE tmp = rb_check_string_type(beg);

re.c

@@ -2753,7 +2753,7 @@ static VALUE
 reg_operand(VALUE s, int check)
 {
     if (SYMBOL_P(s)) {
-	return rb_sym_to_s(s);
+	return rb_sym2str(s);
     }
     else {
 	return (check ? rb_str_to_str : rb_check_string_type)(s);