bug#60237: 30.0.50; tree sitter core dumps when I edebug view a node

[Mickey Petersen <mickey@masteringemacs.org>]

Yuan Fu <casouri@gmail.com> writes:

>> GC has historically never called xmalloc, so the profiler will
>> likely
>> crash upon growing the mark stack as well.  I guess another
>> important
>> question is why ts_delete_parser is calling xmalloc.
>>
>
>> As you see, when we call ts_tree_delete, it calls
>> ts_subtree_release,
>> which in turn calls malloc (redirected into our xmalloc).  Is this
>> expected?  Can you look in the tree-sitter sources and verify that
>> this is OK?
>
> I had a look, and it seems legit. In tree-sitter, a TSTree (or more
> precisely, a Subtree) is just some inlined data plus a refcounted
> pointer to the complete data. This way multiple trees share common
> subtrees/nodes. Eg, when incrementally parsing, you pass in an old
> tree and get a new tree, these two trees will share the unchanged part
> of the tree.

Would that mean we could possibly preserve node instances -- either the real TS ones, or an Emacs-created facsimile -- between incremental parsing? That would be useful for refactoring.