Re: function lca('{}'::ltree[]) caused DB Instance crash

Pierre Ducroquet <p(dot)psql(at)pinaraf(dot)info> writes:
> On Friday, July 13, 2018 12:09:20 PM CEST 李海龙 wrote:
>> contrib_regression=# select lca('{}'::ltree[]);
>> server closed the connection unexpectedly

> There is indeed a bug. The _lca function in _ltree_op.c tries to allocate 0
> bytes of memory, doesn't initialize it and dereference it in lca_inner.
> The attached basic patch fixes it.

I think the defense ought to be in lca_inner not there.

However, I don't understand why this code is returning NULL, rather than
a zero-length ltree, in the case that there's no common prefix. That
doesn't seem consistent to me.

regards, tom lane