Re: What's cooking (draft for #4's issue this month)

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Apr 19, 2021, 02:10 UTC
Message-ID: <YHzmjhLy2QjDefXy@camp.crustytoothpaste.net>
In-Reply-To: <xmqqr1jcrr3c.fsf@gitster.g>

On 2021-04-15 at 06:37:11, Junio C Hamano wrote:

Show 12 quoted lines

> I actually do appreciate the topic to be in 'seen', as these
> integration exercises tend to serve as an early warning for
> impending messy conflicts I'll need to be worried about.
> 
> I do worry about the memory requirement bloat of the object_id
> structure, as we do need to keep one instance per object in-core,
> but the squashable fix for the reftable topic given by Patrick
> to replace use of hashcpy() with oidread() is still a good idea even
> if we are going to use a different mechanism to keep track of which
> object_id instance uses what hash algorithm, so again I am happy to
> have seen your bc/hash-transition-interop-part-1 topic and had an
> early chance to make it collide with others ;-)

I'm still working on a full reroll for the series including performance measurements (since this took me much longer than I expected it would), but I wanted to include a patch for the segfault below to keep things tidy in the mean time. I should point out that this doesn't appear to crash when running the testsuite in SHA-256 mode for reasons I'm not sure about, which explains why I didn't see it originally.

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: "brian m. carlson" <sandals@crustytoothpaste.net>
Date: Sun, 18 Apr 2021 22:56:04 +0000
Subject: [PATCH] http-push: set algorithm when reading object ID

In most places in the codebase, we use oidread to properly read an object ID into a struct object_id. However, in the HTTP code, we end up needing to parse a loose object path with a slash in it, so we can't do that. Let's instead explicitly set the algorithm in this function so we can rely on it in the future.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 http-push.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/http-push.c b/http-push.c
index b60d5fcc85..5675cd7708 100644
--- a/http-push.c
+++ b/http-push.c
@@ -1022,6 +1022,8 @@ static void remote_ls(const char *path, int flags,
 /* extract hex from sharded "xx/x{38}" filename */
 static int get_oid_hex_from_objpath(const char *path, struct object_id *oid)
 {
+	oid->algo = hash_algo_by_ptr(the_hash_algo);
+
 	if (strlen(path) != the_hash_algo->hexsz + 1)
 		return -1;
 
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-- 
brian m. carlson (he/him or they/them)
Houston, Texas, US