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    commit 9f6d8845df3f81e2bc86f593a2f93e098422b2fa
    parent f0398db4d172e838ef4b4ae55db3fb6a6fee6717
    Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
    Date:   Fri,  6 Nov 2015 20:01:00 +0100

    Fix ttywrite()

    ttywrite was assuming that if it could not write then it could
    read, but this is not necessarily true, there are some situations
    where you cannot read or write. The correct behaviour is to detect
    if you can read or/and write.

    Diffstat:
    Mst.c | 38++++++++++++++++++++------------------

    1 file changed, 20 insertions(+), 18 deletions(-)
    diff --git a/st.c b/st.c
    @@ -415,7 +415,7 @@ static int32_t tdefcolor(int *, int *, int);
     static void tdeftran(char);
     static inline int match(uint, uint);
     static void ttynew(void);
    -static void ttyread(void);
    +static size_t ttyread(void);
     static void ttyresize(void);
     static void ttysend(char *, size_t);
     static void ttywrite(const char *, size_t);
    @@ -1464,7 +1464,7 @@ ttynew(void)
     	}
     }

    -void
    +size_t
     ttyread(void)
     {
     	static char buf[BUFSIZ];
    @@ -1489,14 +1489,16 @@ ttyread(void)

     	/* keep any uncomplete utf8 char for the next call */
     	memmove(buf, ptr, buflen);
    +
    +	return ret;
     }

     void
     ttywrite(const char *s, size_t n)
     {
    -	fd_set wfd;
    -	struct timespec tv;
    +	fd_set wfd, rfd;
     	ssize_t r;
    +	size_t lim = 256;

     	/*
     	 * Remember that we are using a pty, which might be a modem line.
    @@ -1506,38 +1508,34 @@ ttywrite(const char *s, size_t n)
     	 */
     	while (n > 0) {
     		FD_ZERO(&wfd);
    +		FD_ZERO(&rfd);
     		FD_SET(cmdfd, &wfd);
    -		tv.tv_sec = 0;
    -		tv.tv_nsec = 0;
    +		FD_SET(cmdfd, &rfd);

     		/* Check if we can write. */
    -		if (pselect(cmdfd+1, NULL, &wfd, NULL, &tv, NULL) < 0) {
    +		if (pselect(cmdfd+1, &rfd, &wfd, NULL, NULL, NULL) < 0) {
     			if (errno == EINTR)
     				continue;
     			die("select failed: %s\n", strerror(errno));
     		}
    -		if(!FD_ISSET(cmdfd, &wfd)) {
    -			/* No, then free some buffer space. */
    -			ttyread();
    -		} else {
    +		if (FD_ISSET(cmdfd, &rfd))
    +			lim = ttyread();
    +		if (FD_ISSET(cmdfd, &wfd)) {
     			/*
     			 * Only write 256 bytes at maximum. This seems to be a
     			 * reasonable value for a serial line. Bigger values
     			 * might clog the I/O.
     			 */
    -			r = write(cmdfd, s, (n < 256)? n : 256);
    -			if (r < 0) {
    -				die("write error on tty: %s\n",
    -						strerror(errno));
    -			}
    +			if ((r = write(cmdfd, s, (n < 256)? n : 256)) < 0)
    +				goto write_error;
     			if (r < n) {
     				/*
     				 * We weren't able to write out everything.
     				 * This means the buffer is getting full
     				 * again. Empty it.
     				 */
    -				if (n < 256)
    -					ttyread();
    +				if (n < lim)
    +					lim = ttyread();
     				n -= r;
     				s += r;
     			} else {
    @@ -1546,6 +1544,10 @@ ttywrite(const char *s, size_t n)
     			}
     		}
     	}
    +	return;
    +
    +write_error:
    +	die("write error on tty: %s\n", strerror(errno));
     }

     void