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buffer: evbuffer_add_buffer(): clean empty chains from destination buffer

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@EMPanisset reported a problem (#358) with evbuffer_remove_buffer(), but
actually I think that the problem is in evbuffer_add_buffer() which introduces
this empty chain, all other callers (except evbuffer_prepend_buffer(), but it
doesn't have this problem though) should be safe.

And FWIW the only API that allows empty chains is evbuffer_add_reference(), and
we can add check there to avoid such issues, but for now I leaved this without
fixing, since I think that evbuffer_add_reference() with empty chains can be
used as a barrier (but this can be tricky).

Fixes: regress evbuffer/remove_buffer_with_empty2
v2: introduce/fixes evbuffer/add_buffer_with_empty
This commit is contained in:
Azat Khuzhin 2016-06-07 18:31:48 +03:00
parent a272bc4227
commit 26fd9321cf
1 changed files with 6 additions and 2 deletions
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8
buffer.c
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@ -885,9 +885,13 @@ APPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
{
ASSERT_EVBUFFER_LOCKED(dst);
ASSERT_EVBUFFER_LOCKED(src);
dst->last->next = src->first;
struct evbuffer_chain **chp;
chp = evbuffer_free_trailing_empty_chains(dst);
*chp = src->first;
if (src->last_with_datap == &src->first)
dst->last_with_datap = &dst->last->next;
dst->last_with_datap = chp;
else
dst->last_with_datap = src->last_with_datap;
dst->last = src->last;