[Scons-users] Scanners

William Blevins wblevins001 at gmail.com
Wed Jan 20 09:36:17 EST 2016


The only cases I know about the number of dependencies changing versus the
order.

On Wed, Jan 20, 2016 at 2:20 PM, Brian Cody <brian.j.cody at gmail.com> wrote:

> Silly question--does the implicit dependency order actually matter? I know
> the sources list does. I ask because I've made plenty of scanners and I've
> never knowingly run into a rebuild due to the implicit dependency order
> changing.
> On Jan 20, 2016 9:08 AM, "Tom Tanner (BLOOMBERG/ LONDON)" <
> ttanner2 at bloomberg.net> wrote:
>
>> There are many things that can cause the generated lists of dependencies
>> to change order. mostly these are concerned with getting lists from glob,
>> but it also can happen if you change the scanners mechanism which can
>> result in getting the same list but in a different order. I changed my
>> python scanner recently to use the python ast library to determine imports,
>> rather than regexes. This works great, but it finds and process things in a
>> slightly different order to how it used to
>>
>> From: wblevins001 at gmail.com At: Jan 20 2016 13:52:54
>> To: Tom Tanner (BLOOMBERG/ LONDON) <ttanner2 at bloomberg.net>,
>> scons-users at scons.org
>> Subject: Re: [Scons-users] Scanners
>>
>> I don't believe there is a magic switch for this. I assume the real issue
>> is that the order of the dependencies must always be the same, and not
>> necessarily sorted alphabetically. What tool are you using that requires
>> sorting? Is this related to caching?
>>
>> V/R,
>> William
>>
>>
>>
>> On Wed, Jan 20, 2016 at 11:22 AM, Tom Tanner (BLOOMBERG/ LONDON) <
>> ttanner2 at bloomberg.net> wrote:
>>
>>> Is there any way to tell the Scanner class to sort the list of scanned
>>> dependencies? I have a hand written scanner and it has to sort the
>>> dependencies it returns so as not to get unexpected rebuilds depending on
>>> the vagaries of todays choice of filing system and how python has decided
>>> to order dictionaries today.
>>>
>>> But even that isn't always enough as the scanner is recursive so it can
>>> possibly build multiple lists which are individually sorted but the total
>>> result isn't.
>>>
>>> But at least specifically in my case, and possibly in others, the order
>>> of the dependencies isn't important.
>>>
>>> Note: I'm using the scanner factory to create my scanner which I see is
>>> sort-of-deprecated, but it's the one I found the documentation when writing
>>> my scanner in the first place.
>>>
>>>
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>>
>>
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