adns_processwriteable: assert that write did not write more than we asked

This is better than proceeding to make tcpsend.used negative.

Should this ever happens, which it doesn't except under AFL, because
of a bug in hfuzzraw.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/src/event.c b/src/event.c
index 8cfaef5353b54af288e674a7d2d0c816e6dfbc0b..95386f42c4fed8351a939290cd85dcfdf5bed53b 100644 (file)
--- a/src/event.c
+++ b/src/event.c
@@ -488,6 +488,7 @@ int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
        adns__tcp_broken(ads,"write",strerror(errno));
        r= 0; goto xit;
       } else if (r>0) {
+       assert(r <= ads->tcpsend.used);
        ads->tcpsend.used -= r;
        memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
       }