Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes:
> I attempted to make index_state->cache[] a "const struct cache_entry **"
> to find out how existing entries in index are modified and where. The
> question I have is what do we do if we really need to keep track of on-disk
> changes in the index. The result is
>
> - diff-lib.c: setting CE_UPTODATE
>
> - name-hash.c: setting CE_HASHED
>
> - preload-index.c, read-cache.c, unpack-trees.c and
> builtin/update-index: obvious
>
> - entry.c: write_entry() may refresh the checked out entry via
> fill_stat_cache_info(). This causes "non-const struct cache_entry
> *" in builtin/apply.c, builtin/checkout-index.c and
> builtin/checkout.c
>
> - builtin/ls-files.c: --with-tree changes stagemask and may set
> CE_UPDATE
>
> Of these, write_entry() and its call sites are probably most
> interesting because it modifies on-disk info. But this is stat info
> and can be retrieved via refresh, at least for porcelain
> commands. Other just uses ce_flags for local purposes.
>
> So, keeping track of "dirty" entries is just a matter of setting a
> flag in index modification functions exposed by read-cache.c. Except
> unpack-trees, the rest of the code base does not do anything funny
> behind read-cache's back.
>
> The actual patch is less valueable than the summary above. But if
> anyone wants to re-identify the above sites. Applying this patch, then
> this:
>
> diff --git a/cache.h b/cache.h
> index 430d021..1692891 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -267,7 +267,7 @@ static inline unsigned int canon_mode(unsigned int mode)
> #define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)
>
> struct index_state {
> - struct cache_entry **cache;
> + const struct cache_entry **cache;
> unsigned int version;
> unsigned int cache_nr, cache_alloc, cache_changed;
> struct string_list *resolve_undo;
>
> will help quickly identify them without bogus warnings.
Nicely done and a very interesting result. I quickly eyeballed the
output of
$ git grep -e 'struct cache_entry' --and --not -e 'const struct cache_entry'
and the result matches what I would expect to see.
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