Re: [PATCH v4] merge-recursive: check GIT_MERGE_VERBOSITY only once

[Andrey Okoshkin <a.okoshkin@samsung.com>]

31.10.2017 05:26, Junio C Hamano wrote:
> Junio C Hamano <gitster@pobox.com> writes:
> 
>> That holds true for the code before or after this patch equally.  In
>> other words, that sounds like a justification for rejecting this
>> patch (i.e. explanation of why this change is not needed).
>>
>> If we are worried about another thread calling these functions after
>> the time we call getenv() and before the time we pass the result to
>> strtol(), then I do not think this patch gives a better protection
>> against such race, so I do not think that is why you are doing this.
>>
>> So... why do we want to do this change?  I am puzzled.

I think, the main benefits are:
* Code is more readable, no duplicated calls with the same constant string
argument.
* Code is potentially safer, the second getenv() call may return another
pointer value which could be NULL (and yes, this is an arguable point as it
can be done only artificially).

> For the sake of fairness, I would say that the resulting code may be
> easier to follow and has one less instance of a constant string that
> the compiler cannot statically check if we made a typo.  That's the
> only benefit in this patch as far as I can see.
> 
> The original makes a call to see if the result is NULL, and then
> makes the same call, expecting that we get the same result (not just
> that it is not NULL, but it is the same verbosity request the end
> user made via the environment as the one we checked earlier), and I
> can understand that it feels a bit redundant and ugly.

Yes, you absolutely right.
I believe this patch makes code more beautiful :-)

>>> Signed-off-by: Andrey Okoshkin <a.okoshkin@samsung.com>
>>> Reviewed-by: Stefan Beller <sbeller@google.com>
>>> ---
>>> Added 'reviewed-by' field.
>>>  merge-recursive.c | 7 ++++---
>>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/merge-recursive.c b/merge-recursive.c
>>> index 1494ffdb8..60084e3a0 100644
>>> --- a/merge-recursive.c
>>> +++ b/merge-recursive.c
>>> @@ -2163,6 +2163,7 @@ static void merge_recursive_config(struct merge_options *o)
>>>  
>>>  void init_merge_options(struct merge_options *o)
>>>  {
>>> +	const char *merge_verbosity;
>>>  	memset(o, 0, sizeof(struct merge_options));
>>>  	o->verbosity = 2;
>>>  	o->buffer_output = 1;
>>> @@ -2171,9 +2172,9 @@ void init_merge_options(struct merge_options *o)
>>>  	o->renormalize = 0;
>>>  	o->detect_rename = 1;
>>>  	merge_recursive_config(o);
>>> -	if (getenv("GIT_MERGE_VERBOSITY"))
>>> -		o->verbosity =
>>> -			strtol(getenv("GIT_MERGE_VERBOSITY"), NULL, 10);
>>> +	merge_verbosity = getenv("GIT_MERGE_VERBOSITY");
>>> +	if (merge_verbosity)
>>> +		o->verbosity = strtol(merge_verbosity, NULL, 10);
>>>  	if (o->verbosity >= 5)
>>>  		o->buffer_output = 0;
>>>  	strbuf_init(&o->obuf, 0);
> 
> 
> 

-- 
Best regards,
Andrey Okoshkin