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From: Pranit Bauva <pranit.bauva@gmail.com>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: "Git List" <git@vger.kernel.org>,
	"Christian Couder" <christian.couder@gmail.com>,
	"Christian Couder" <chriscool@tuxfamily.org>,
	"Lars Schneider" <larsxschneider@gmail.com>,
	"Torsten Bögershausen" <tboegi@web.de>
Subject: Re: [PATCH v2 3/6] wrapper: move is_empty_file() from builtin/am.c
Date: Thu, 16 Jun 2016 00:10:03 +0530	[thread overview]
Message-ID: <CAFZEwPOkojqvivXpP7vq6WuMWPAjE1uXruoxsxH76LGT+1Eu4A@mail.gmail.com> (raw)
In-Reply-To: <CAPig+cTu1msxkjBZgLfy9g3+_VF5OzKNDbR0E0zVvopTNe2Q=g@mail.gmail.com>

Hey Eric,

On Wed, Jun 15, 2016 at 11:52 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Wed, Jun 15, 2016 at 10:00 AM, Pranit Bauva <pranit.bauva@gmail.com> wrote:
>> is_empty_file() can help to refactor a lot of code. Also it is quite
>> helpful while converting shell scripts which use `test -s`. Since
>
> As justification, "can help to refactor a lot of code" is very
> nebulous. It would be better to give a concrete reason for moving the
> function, such as explaining that the functionality will be needed by
> the "git bisect" port to C.

Sure I can include that.

>> is_empty_file() is now a "library" function, its inappropriate to die() so
>> instead error_errno() is used to convey the message to stderr while the
>> appropriate boolean value is returned.
>>
>> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
>> ---
>> diff --git a/builtin/am.c b/builtin/am.c
>> @@ -30,22 +30,6 @@
>>  /**
>> - * Returns 1 if the file is empty or does not exist, 0 otherwise.
>> - */
>> -static int is_empty_file(const char *filename)
>> -{
>> -       struct stat st;
>> -
>> -       if (stat(filename, &st) < 0) {
>> -               if (errno == ENOENT)
>> -                       return 1;
>> -               die_errno(_("could not stat %s"), filename);
>> -       }
>> -
>> -       return !st.st_size;
>> -}
>
> So, the original function die()'d for unexpected errors, but the
> rewrite does not. This is a big behavior change. To account for such a
> change in behavior I'd expect to see git-am updated to die() on its
> own for such failures, but no such changes are present in this patch.
> More about this below...
>
>> diff --git a/wrapper.c b/wrapper.c
>> @@ -696,3 +696,16 @@ void sleep_millisec(int millisec)
>> +int is_empty_file(const char *filename)
>> +{
>> +       struct stat st;
>> +
>> +       if (stat(filename, &st) < 0) {
>> +               if (errno == ENOENT)
>> +                       return 1;
>> +               error_errno(_("could not stat %s"), filename);
>
> Mental note: There is no 'return' in front of error_errno(), so the
> function does not exit here...

This is purposely as I want to keep this function to return only
boolean values ( 0 or 1).

>> +       }
>> +
>> +       return !st.st_size;
>> +}
>
> If stat() returns some error other than ENOENT, then the value of 'st'
> will be undefined, yet this return statement accesses its 'st_size'
> field, which is clearly a bad thing to do.
>
> You either need to return a designated value (such as -1) upon errors
> other than ENOENT (and update the documentation to mention -1) so that
> the caller can decided what to do, or die() as the original did. While
> it's true that die()'ing is not necessarily friendly in library code,
> it may be acceptable until such time that you find a caller which
> needs different behavior.

I didn't realize the complexity the patch carried with itself before.
I probably shouldn't fidget with am code right now, its a work better
left to who are converting the code to library code. I think its the
best fit for this situation to leave it as die()'ing.

Regards,
Pranit Bauva

  reply	other threads:[~2016-06-15 18:40 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 20:54 [PATCH 1/4] bisect--helper: `bisect_clean_state` shell function in C Pranit Bauva
2016-06-07 20:54 ` [PATCH 2/4] t6030: explicitly test for bisection cleanup Pranit Bauva
2016-06-07 23:21   ` Eric Sunshine
2016-06-08  8:07     ` Pranit Bauva
2016-06-08  8:17       ` Eric Sunshine
2016-06-08 10:20         ` Pranit Bauva
2016-06-07 20:54 ` [PATCH 3/4] dir: introduce file_size() to check the size of file Pranit Bauva
2016-06-08  7:37   ` Eric Sunshine
2016-06-08  7:57     ` Pranit Bauva
2016-06-08  8:13       ` Eric Sunshine
2016-06-08 10:03         ` Christian Couder
2016-06-08  8:17       ` Torsten Bögershausen
2016-06-08 13:08         ` Pranit Bauva
2016-06-12 10:44           ` Torsten Bögershausen
2016-06-13  6:21             ` Pranit Bauva
2016-06-07 20:54 ` [PATCH 4/4] bisect--helper: `bisect_reset` shell function in C Pranit Bauva
2016-06-08  7:59   ` Eric Sunshine
2016-06-08  9:51     ` Christian Couder
2016-06-08  9:53       ` Christian Couder
2016-06-08 17:50       ` Eric Sunshine
2016-06-08 13:20     ` Pranit Bauva
2016-06-08 17:53       ` Eric Sunshine
2016-06-08 18:04         ` Pranit Bauva
2016-06-07 22:31 ` [PATCH 1/4] bisect--helper: `bisect_clean_state` " Eric Sunshine
2016-06-08  1:51   ` Eric Sunshine
2016-06-08  7:46   ` Pranit Bauva
2016-06-08  8:02     ` Eric Sunshine
2016-06-08  8:09       ` Pranit Bauva
2016-06-08  9:41       ` Christian Couder
2016-06-08 17:59         ` Eric Sunshine
2016-06-08 18:04           ` Pranit Bauva
2016-06-15 14:00 ` [PATCH v2 0/6] convert various shell functions in git-bisect to C Pranit Bauva
2016-06-15 14:00   ` [PATCH v2 1/6] bisect--helper: `bisect_clean_state` shell function in C Pranit Bauva
2016-06-15 18:04     ` Eric Sunshine
2016-06-15 18:47       ` Pranit Bauva
2016-06-15 20:22         ` Eric Sunshine
2016-06-15 14:00   ` [PATCH v2 2/6] t6030: explicitly test for bisection cleanup Pranit Bauva
2016-06-15 14:00   ` [PATCH v2 3/6] wrapper: move is_empty_file() from builtin/am.c Pranit Bauva
2016-06-15 18:12     ` Junio C Hamano
2016-06-15 18:15       ` Pranit Bauva
2016-06-15 18:22     ` Eric Sunshine
2016-06-15 18:40       ` Pranit Bauva [this message]
2016-06-15 14:00   ` [PATCH v2 4/6] bisect--helper: `bisect_reset` shell function in C Pranit Bauva
2016-06-15 21:05     ` Eric Sunshine
2016-06-16 19:06       ` Pranit Bauva
2016-06-15 14:00   ` [PATCH v2 5/6] bisect--helper: `is_expected_rev` & `check_expected_revs` " Pranit Bauva
2016-06-15 21:14     ` Eric Sunshine
2016-06-16 19:05       ` Pranit Bauva
2016-06-16 19:16         ` Eric Sunshine
2016-06-16 19:25           ` Pranit Bauva
2016-06-16 20:47             ` Christian Couder
2016-06-17 12:49               ` Pranit Bauva
2016-06-15 14:00   ` [PATCH v2 6/6] bisect--helper: `bisect_write` " Pranit Bauva
2016-06-16 18:55     ` Eric Sunshine
2016-06-16 19:01       ` Pranit Bauva
2016-06-16 20:38         ` Christian Couder
2016-06-17 13:10           ` Pranit Bauva
2016-06-15 17:53   ` [PATCH v2 0/6] convert various shell functions in git-bisect to C Eric Sunshine
2016-06-15 18:09     ` Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 " Pranit Bauva
2016-07-06 20:25   ` [PATCH v4 " Pranit Bauva
2016-07-06 20:25     ` [PATCH v4 1/6] bisect--helper: `bisect_clean_state` shell function in C Pranit Bauva
2016-07-06 20:25     ` [PATCH v4 2/6] t6030: explicitly test for bisection cleanup Pranit Bauva
2016-07-11 19:16       ` Junio C Hamano
2016-07-06 20:25     ` [PATCH v4 3/6] wrapper: move is_empty_file() and rename it as is_empty_or_missing_file() Pranit Bauva
2016-07-06 20:25     ` [PATCH v4 4/6] bisect--helper: `bisect_reset` shell function in C Pranit Bauva
2016-07-06 20:25     ` [PATCH v4 5/6] bisect--helper: `is_expected_rev` & `check_expected_revs` " Pranit Bauva
2016-07-06 20:25     ` [PATCH v4 6/6] bisect--helper: `bisect_write` " Pranit Bauva
2016-07-11 19:19     ` [PATCH v4 0/6] convert various shell functions in git-bisect to C Junio C Hamano
2016-06-26 12:23 ` [PATCH v3 1/6] bisect--helper: `bisect_clean_state` shell function in C Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 2/6] t6030: explicitly test for bisection cleanup Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 3/6] wrapper: move is_empty_file() and rename it as is_empty_or_missing_file() Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 4/6] bisect--helper: `bisect_reset` shell function in C Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 5/6] bisect--helper: `is_expected_rev` & `check_expected_revs` " Pranit Bauva
2016-06-26 12:23 ` [PATCH v3 6/6] bisect--helper: `bisect_write` " Pranit Bauva

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