Make sbuf_printf update the len and maxsz internal fields

* sbuf_printf updated the .data field with a freshly allocated string,
  but didn't bother setting the .len and .maxsz fields of the sbuf.
  Calling other sbuf_* functions on the same sbuf could lead to erratic
  behavior and data corruption.  eg. in init_screen, the screen's
  display_string ended up corrupted, using putenv ratpoison couldn't
  override the DISPLAY environment variable in child processes anymore,
  introducing a regression on multi-screen setups.

Bug reported and cause tracked down by William Yodlowsky, the maintainer
of the OpenBSD ratpoison port.  Thanks!

1 files changed, 3 insertions, 0 deletions

diff --git a/src/sbuf.c b/src/sbuf.c
index 77b8a04..661ec83 100644
--- a/src/sbuf.c
+++ b/src/sbuf.c
@@ -123,6 +123,9 @@ sbuf_printf (struct sbuf *b, char *fmt, ...)
   b->data = xvsprintf (fmt, ap);
   va_end (ap);
 
+  b->len = strlen (b->data);
+  b->maxsz = b->len + 1;
+
   return b->data;
 }