Subject: Re: [PATCH v3][GSOC] fsck: use bitwise-or assignment operator to set flag

From: Junio C Hamano <[email-masked]>
Date: Thu, 20 Mar 2014 11:20:47 -0700

Hiroyuki Sano <[email-masked]> writes:

> fsck_tree() has two different ways to set a flag,
> which are the followings:
>
>   1. Using a if-statement that guards assignment.
>
>   2. Using a bitwise-or assignment operator.
>
> Currently, many with the former way,
> and one with the latter way.
>
> In this patch, unify them to the latter way,
> because it makes the code shorter and easier to read,
> and it is brief and to the point.

Two issues:

 * "In this patch," is redundant.

 * "it is brief and to the point" are equally applicable to both
   styles, so that is not a *reason* to choose one over the other.

If a condition were *not* brief and to the point, then a rewrite to
the latter style will make the resulting code worse:

	if (a very complex condition
            that potentially have to consume a
            lot of brain-cycles to understand) {
		has_that_condition = 1;
	}

is a lot easier to extend than

	has_that_condition = (a very complex condition
                              that potentially have to consume a
                              lot of brain-cycles to understand);

because it is a lot more likely that we would need to later extend
such a complex condition is more likely than a simple singleton
condition, and we could end up with

	if (a very complex condition
            that potentially have to consume a
            lot of brain-cycles to understand) {
		futher computation to check if
                the condition really holds
                will be added here later
                if (does that condition really hold true?)
			has_that_condition = 1;
	}

which may be harder to express in the latter form.

In other words, "it is brief and to the point" merely _allows_ these
statements to be expressed in the latter form; it does not say
anything about which is better between the former and the latter.

> Signed-off-by: Hiroyuki Sano <[email-masked]>
> ---
>  fsck.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/fsck.c b/fsck.c
> index b3022ad..abed62b 100644
> --- a/fsck.c
> +++ b/fsck.c
> @@ -165,18 +165,12 @@ static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
>  
>  		sha1 = tree_entry_extract(&desc, &name, &mode);
>  
> -		if (is_null_sha1(sha1))
> -			has_null_sha1 = 1;
> -		if (strchr(name, '/'))
> -			has_full_path = 1;
> -		if (!*name)
> -			has_empty_name = 1;
> -		if (!strcmp(name, "."))
> -			has_dot = 1;
> -		if (!strcmp(name, ".."))
> -			has_dotdot = 1;
> -		if (!strcmp(name, ".git"))
> -			has_dotgit = 1;
> +		has_null_sha1 |= is_null_sha1(sha1);
> +		has_full_path |= !!strchr(name, '/');
> +		has_empty_name |= !*name;
> +		has_dot |= !strcmp(name, ".");
> +		has_dotdot |= !strcmp(name, "..");
> +		has_dotgit |= !strcmp(name, ".git");
>  		has_zero_pad |= *(char *)desc.buffer == '0';
>  		update_tree_entry(&desc);