Bug in peek-char?

[forcer <forcer@mindless.com>]

Lately i noticed something funny in guile...

guile> (define (test char)
...     (with-input-from-string (make-string 1 char)
...			(lambda ()
...				(let* ((peeked (peek-char))
...					   (read   (read-char)))
...					(cons peeked read)))))
guile> (test #\177)
(#\ . #\)
guile> (test #\200)
(#\200 . #\-200)
guile> (test #\377)
(#\377 . #<eof>)

R5RS requires that a peek-char followed by a read-char both return
exactly the same value.
The problem is the peek and read, since the behavior is the same on
any port type, not only string ports.

After a bit of diving into the ugly mess of guile ports, i think i
found the problem in ports.h:

struct scm_port_table
{
	[...]
	char *cp;                     /* where to put and get unget chars */
	char *cbufend;                /* points after this struct */
	char cbuf[SCM_INITIAL_CBUF_SIZE]; /* must be last: may grow */
};
	  
The only fix i can see is to declare those buffers to be either
unsigned char or int (int would be saner), and to adjust the accessing
procedures and macros accordingly.

I hope this helps, and keep up the good work,
	-forcer

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