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From: Elijah Newren <newren@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH v2 06/20] merge-ort: implement a very basic collect_merge_info()
Date: Fri, 6 Nov 2020 15:10:07 -0800	[thread overview]
Message-ID: <CABPp-BFkAu6oO5V0jRh=ExuPxBXma1F17zaq-zEaqMagc72Ccw@mail.gmail.com> (raw)
In-Reply-To: <20201106221934.764672-1-jonathantanmy@google.com>

On Fri, Nov 6, 2020 at 2:19 PM Jonathan Tan <jonathantanmy@google.com> wrote:
>
> > diff --git a/merge-ort.c b/merge-ort.c
> > index 537da9f6df..626eb9713e 100644
> > --- a/merge-ort.c
> > +++ b/merge-ort.c
> > @@ -77,13 +77,130 @@ static int err(struct merge_options *opt, const char *err, ...)
> >       return -1;
> >  }
> >
> > +static int collect_merge_info_callback(int n,
> > +                                    unsigned long mask,
> > +                                    unsigned long dirmask,
> > +                                    struct name_entry *names,
> > +                                    struct traverse_info *info)
> > +{
>
> [snip]
>
> > +     unsigned mbase_null = !(mask & 1);
> > +     unsigned side1_null = !(mask & 2);
> > +     unsigned side2_null = !(mask & 4);
>
> Should these be "int"?

Does the type matter, particularly since "boolean" isn't available?

> > +     /*
> > +      * A bunch of sanity checks verifying that traverse_trees() calls
> > +      * us the way I expect.  Could just remove these at some point,
> > +      * though maybe they are helpful to future code readers.
> > +      */
> > +     assert(mbase_null == is_null_oid(&names[0].oid));
> > +     assert(side1_null == is_null_oid(&names[1].oid));
> > +     assert(side2_null == is_null_oid(&names[2].oid));
> > +     assert(!mbase_null || !side1_null || !side2_null);
> > +     assert(mask > 0 && mask < 8);
>
> These were helpful to me.
>
> > +     /* Other invariant checks, mostly for documentation purposes. */
> > +     assert(mask == (dirmask | filemask));
>
> But not this - filemask was computed in this function, so I need not
> look elsewhere to see that this is correct.
>
> > +     /*
> > +      * TODO: record information about the path other than all zeros,
> > +      * so we can resolve later in process_entries.
> > +      */
> > +     ci = xcalloc(1, sizeof(struct conflict_info));
> > +     strmap_put(&opti->paths, fullpath, ci);
>
> OK - so each entry is a full-size conflict_info to store all relevant
> information. Presumably some of these will be converted later into what
> is effectively a struct merged_info (so, the extra struct conflict_info
> fields are unused but memory is still occupied).
>
> I do see that in patch 10, there is an optimization that directly
> allocates the smaller struct merged_info when it is known at this point
> that there is no conflict.

Yep.  :-)

> [snip rest of function]
>
> >  static int collect_merge_info(struct merge_options *opt,
> >                             struct tree *merge_base,
> >                             struct tree *side1,
> >                             struct tree *side2)
> >  {
> > -     /* TODO: Implement this using traverse_trees() */
> > -     die("Not yet implemented.");
> > +     int ret;
> > +     struct tree_desc t[3];
> > +     struct traverse_info info;
> > +     char *toplevel_dir_placeholder = "";
> > +
> > +     opt->priv->current_dir_name = toplevel_dir_placeholder;
> > +     setup_traverse_info(&info, toplevel_dir_placeholder);
>
> I thought that this was written like this (instead of inlining the 2
> double-quotes) to ensure that the string-equality-is-pointer-equality
> characteristic holds, but I see that that characteristic is for
> directory_name in struct merged_info, not current_dir_name in struct
> merge_options_internal. Any reason for not inlining ""?

You're really digging in; I love it.  From setup_path_info(), the
directory_name is set from the current_dir_name:
        path_info->merged.directory_name = current_dir_name;
(and if you follow where the current_dir_name parameter gets its value
from, you find that it came indirectly from
opt->priv->current_dir_name), so current_dir_name must meet all the
requirements on merge_info's directory_name field.

Perhaps there's still some kind of additional simplification possible
here, but directory rename detection is an area that has to take some
special care around this requirement.  I simplified the code a little
bit in this area as I was trying to break off a good first 20 patches
to submit, but even if we can simplify it more, the structure is just
going to come back later.

  reply	other threads:[~2020-11-06 23:10 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-02 20:43 [PATCH v2 00/20] fundamentals of merge-ort implementation Elijah Newren
2020-11-02 20:43 ` [PATCH v2 01/20] merge-ort: setup basic internal data structures Elijah Newren
2020-11-06 22:05   ` Jonathan Tan
2020-11-06 22:45     ` Elijah Newren
2020-11-09 20:55       ` Jonathan Tan
2020-11-02 20:43 ` [PATCH v2 02/20] merge-ort: add some high-level algorithm structure Elijah Newren
2020-11-02 20:43 ` [PATCH v2 03/20] merge-ort: port merge_start() from merge-recursive Elijah Newren
2020-11-11 13:52   ` Derrick Stolee
2020-11-11 16:22     ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 04/20] merge-ort: use histogram diff Elijah Newren
2020-11-11 13:54   ` Derrick Stolee
2020-11-11 16:47     ` Elijah Newren
2020-11-11 16:51       ` Derrick Stolee
2020-11-11 17:03         ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 05/20] merge-ort: add an err() function similar to one from merge-recursive Elijah Newren
2020-11-11 13:58   ` Derrick Stolee
2020-11-11 17:07     ` Elijah Newren
2020-11-11 17:10       ` Derrick Stolee
2020-11-02 20:43 ` [PATCH v2 06/20] merge-ort: implement a very basic collect_merge_info() Elijah Newren
2020-11-06 22:19   ` Jonathan Tan
2020-11-06 23:10     ` Elijah Newren [this message]
2020-11-09 20:59       ` Jonathan Tan
2020-11-11 14:38   ` Derrick Stolee
2020-11-11 17:02     ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 07/20] merge-ort: avoid repeating fill_tree_descriptor() on the same tree Elijah Newren
2020-11-11 14:51   ` Derrick Stolee
2020-11-11 17:13     ` Elijah Newren
2020-11-11 17:21       ` Eric Sunshine
2020-11-02 20:43 ` [PATCH v2 08/20] merge-ort: compute a few more useful fields for collect_merge_info Elijah Newren
2020-11-06 22:52   ` Jonathan Tan
2020-11-06 23:41     ` Elijah Newren
2020-11-09 22:04       ` Jonathan Tan
2020-11-09 23:05         ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 09/20] merge-ort: record stage and auxiliary info for every path Elijah Newren
2020-11-06 22:58   ` Jonathan Tan
2020-11-07  0:26     ` Elijah Newren
2020-11-09 22:09       ` Jonathan Tan
2020-11-09 23:08         ` Elijah Newren
2020-11-11 15:26   ` Derrick Stolee
2020-11-11 18:16     ` Elijah Newren
2020-11-11 22:06       ` Elijah Newren
2020-11-12 18:23         ` Derrick Stolee
2020-11-12 18:39       ` Derrick Stolee
2020-11-02 20:43 ` [PATCH v2 10/20] merge-ort: avoid recursing into identical trees Elijah Newren
2020-11-11 15:31   ` Derrick Stolee
2020-11-02 20:43 ` [PATCH v2 11/20] merge-ort: add a preliminary simple process_entries() implementation Elijah Newren
2020-11-11 19:51   ` Jonathan Tan
2020-11-12  1:48     ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 12/20] merge-ort: have process_entries operate in a defined order Elijah Newren
2020-11-11 16:09   ` Derrick Stolee
2020-11-11 18:58     ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 13/20] merge-ort: step 1 of tree writing -- record basenames, modes, and oids Elijah Newren
2020-11-11 20:01   ` Jonathan Tan
2020-11-11 20:24     ` Elijah Newren
2020-11-12 20:39       ` Jonathan Tan
2020-11-02 20:43 ` [PATCH v2 14/20] merge-ort: step 2 of tree writing -- function to create tree object Elijah Newren
2020-11-11 20:47   ` Jonathan Tan
2020-11-11 21:21     ` Elijah Newren
2020-11-02 20:43 ` [PATCH v2 15/20] merge-ort: step 3 of tree writing -- handling subdirectories as we go Elijah Newren
2020-11-12 20:15   ` Jonathan Tan
2020-11-12 22:30     ` Elijah Newren
2020-11-24 20:19       ` Elijah Newren
2020-11-25  2:07         ` Jonathan Tan
2020-11-26 18:13           ` Elijah Newren
2020-11-30 18:41             ` Jonathan Tan
2020-11-02 20:43 ` [PATCH v2 16/20] merge-ort: basic outline for merge_switch_to_result() Elijah Newren
2020-11-02 20:43 ` [PATCH v2 17/20] merge-ort: add implementation of checkout() Elijah Newren
2020-11-02 20:43 ` [PATCH v2 18/20] tree: enable cmp_cache_name_compare() to be used elsewhere Elijah Newren
2020-11-02 20:43 ` [PATCH v2 19/20] merge-ort: add implementation of record_unmerged_index_entries() Elijah Newren
2020-11-02 20:43 ` [PATCH v2 20/20] merge-ort: free data structures in merge_finalize() Elijah Newren
2020-11-03 14:49 ` [PATCH v2 00/20] fundamentals of merge-ort implementation Derrick Stolee
2020-11-03 16:36   ` Elijah Newren
2020-11-07  6:06     ` Elijah Newren
2020-11-07 15:02       ` Derrick Stolee
2020-11-07 19:39         ` Elijah Newren
2020-11-09 12:30           ` Derrick Stolee
2020-11-09 17:13             ` Elijah Newren
2020-11-09 19:51               ` Derrick Stolee
2020-11-09 22:44                 ` Elijah Newren
2020-11-11 17:08 ` Derrick Stolee
2020-11-11 18:35   ` Elijah Newren
2020-11-11 20:48     ` Derrick Stolee
2020-11-11 21:18       ` Elijah Newren
2020-11-29  7:43 [PATCH " Elijah Newren via GitGitGadget
2020-12-04 20:47 ` [PATCH v2 " Elijah Newren via GitGitGadget
2020-12-04 20:47   ` [PATCH v2 06/20] merge-ort: implement a very basic collect_merge_info() Elijah Newren via GitGitGadget

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