Re: [PATCH v3 1/3] refs: keep track of unresolved reference value in iterators

> "John Cai via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> diff --git a/refs/files-backend.c b/refs/files-backend.c
>> index aa52d9be7c7..5ed69c23f74 100644
>> --- a/refs/files-backend.c
>> +++ b/refs/files-backend.c
>> @@ -245,9 +245,11 @@ static void loose_fill_ref_dir_regular_file(struct files_ref_store *refs,
>>  {
>>  	struct object_id oid;
>>  	int flag;
>> -
>> -	if (!refs_resolve_ref_unsafe(&refs->base, refname, RESOLVE_REF_READING,
>
> Here, we had a nice blank line that separated the decls and the
> first statement.
>
>> -				     &oid, &flag)) {
>> +	const char *referent = refs_resolve_ref_unsafe(&refs->base,
>> +						       refname,
>> +						       RESOLVE_REF_READING,
>> +						       &oid, &flag);
>> +	if (!referent) {
>
> We lost it here, though.

>
>>  		oidclr(&oid, the_repository->hash_algo);
>>  		flag |= REF_ISBROKEN;
>>  	} else if (is_null_oid(&oid)) {
>> @@ -268,7 +270,11 @@ static void loose_fill_ref_dir_regular_file(struct files_ref_store *refs,
>>  		oidclr(&oid, the_repository->hash_algo);
>>  		flag |= REF_BAD_NAME | REF_ISBROKEN;
>>  	}
>> -	add_entry_to_dir(dir, create_ref_entry(refname, &oid, flag));
>> +
>> +	if (!(flag & REF_ISSYMREF))
>> +		referent = NULL;
>
> OK, this is new in this round.  The idea is that everybody else can
> rely on the invariant that the referent being NULL is equivalent to
> REF_ISSYMREF bit in flag word being off from here on.
>
>> +	add_entry_to_dir(dir, create_ref_entry(refname, referent, &oid, flag));
>>  }
>>
>>  /*
>> @@ -886,6 +892,11 @@ static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
>>  		iter->base.refname = iter->iter0->refname;
>>  		iter->base.oid = iter->iter0->oid;
>>  		iter->base.flags = iter->iter0->flags;
>> +		if (iter->iter0->flags & REF_ISSYMREF)
>> +			iter->base.referent = iter->iter0->referent;
>> +		else
>> +			iter->base.referent = NULL;
>>  		return ITER_OK;
>>  	}
>
> Hmph, why not an unconditional
>
> 		iter->base.referent = iter->iter0->referent;
>
> instead?  This code is making sure (iter->base.flags & REF_ISSYMREF)
> is directly linked to non-NULL-ness or iter->base.referent, and we
> want to make everybody take it as invariant.  Shouldn't this code
> also rely on the same invariant?  If iter-iter0->referent is NULL,
> iter->iter0->flag has REF_ISSYMREF bit off, and vice versa.