Re: [PATCH 1/2] bisect--helper: `is_expected_rev` shell function in C

[Pranit Bauva <pranit.bauva@gmail.com>]

Hey Eric,

On Fri, Jun 10, 2016 at 3:03 AM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Wed, Jun 8, 2016 at 11:24 AM, Pranit Bauva <pranit.bauva@gmail.com> wrote:
>> Reimplement `is_expected_rev` shell function in C. This will further be
>> called from `check_expected_revs` function. This is a quite small
>> function thus subcommand facility is redundant.
>
> This patch should be squashed into patch 2/2, as it is otherwise
> pointless without that patch, and merely adds dead code.

Sure I will squash and will explain it in the commit message.

>> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
>> ---
>> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
>> @@ -160,6 +160,20 @@ int bisect_reset(const char *commit)
>> +static int is_expected_rev(const char *expected_hex)
>> +{
>> +       struct strbuf actual_hex = STRBUF_INIT;
>> +
>> +       if (!file_exists(git_path_bisect_expected_rev()))
>> +               return 0;
>
> Invoking file_exists() seems unnecessarily redundant when you can
> discern effectively the same by checking the return value of
> strbuf_read_file() below. I'd drop the file_exists() check altogether.

I wanted to imitate the code. But I guess it would actually be better
if I drop this file_exists().

>> +       if (!strbuf_read_file(&actual_hex, git_path_bisect_expected_rev(), 0))
>> +               return 0;
>
> What exactly is this trying to do? Considering that strbuf_read_file()
> returns -1 upon error, otherwise the number of bytes read, if I'm
> reading this correctly, is_expected_rev() returns false if
> strbuf_read_file() encounters an error (which is fine) but also when
> it successfully reads the file and its content length is non-zero
> (which is very odd).
>
>> +       strbuf_trim(&actual_hex);
>> +       return !strcmp(actual_hex.buf, expected_hex);
>
> Thus, it only ever gets to this point if the file exists but is empty,
> which is very unlikely to match 'expected_hex'. I could understand it
> if you checked the result of strbuf_read_file() with <0 or even <=0,
> but the current code doesn't make sense to me.
>
> Am I misunderstanding?


Definitely not. Thanks for pointing it out. :) It went off my head
that strbuf_read_file returns the bytes it reads. Also the code
comment regarding strbuf_read_file does not mention it which probably
misguided me. I should also send a fixing patch so that someone else
does not fall into this like I did.

I will also release the 'actual_hex'.

Thanks for your comments!

Regards,
Pranit Bauva