From: Jeff King <peff@peff.net>
Date: Wed, 23 Jul 2025 23:52:34 GMT
Subject: Re: [PATCH] ref-iterator-seek: correctly initialize the prefix_state for a new level
Message-ID: <20250723235234.GA592873@coredump.intra.peff.net>
In-Reply-To: <xmqqldoelgnd.fsf_-_@gitster.g>

On Wed, Jul 23, 2025 at 02:51:50PM -0700, Junio C Hamano wrote:

> When cache_ref_iterator_seek() "jumps" to a middle of the sorted ref
> list, it forgets to set the .prefix_state member of the new
> (i.e. deeper) level it just initialized.  This later causes
> cache_ref_iterator_advance() to look at this uninitialized member
> to base its decision on what to do next.
> 
> Kyle Lippincott [*] and Jeff King noticed this with MSAN and
> Valgrind, and Karthik Nayak as the original author located exactly
> where the missing initialization is.

This explanation makes sense to me (from my admittedly rusty view of the
ref iteration code). And certainly the patch looks right.

-Peff