[Scons-users] What affects rebuilding?

[Bill Deegan]

Douwe,

Can you provide a simple SConstruct which reproduces the issue?

Is it possible you are constructing a list of source files and the order of
those files changed?

-Bill

On Tue, Jun 30, 2015 at 11:06 AM, Douwe Gelling <douwegelling at gmail.com>
wrote:

> I have used --debug=explain, which shows me that file a/b/c.cpp was
> removed from the dependency list and file a/b/c.cpp added to the dependency
> list
> and that was why the file had to be recompiled. This was not very
> informative, so I've changed the explain function to print the path field
> of a File object instead of using stringify, and it is comparing an
> original file and a file copied to the variant directory..
>
> On 30 June 2015 at 16:57, Bill Deegan <bill at baddogconsulting.com> wrote:
>
>> Try:
>>
>> scons --debug=explain
>>
>> It should tell you why targets are being built..
>>
>> On Tue, Jun 30, 2015 at 10:38 AM, William Blevins <wblevins001 at gmail.com>
>> wrote:
>>
>>> May also be a VariantDir specific issue.
>>>
>>> V/R,
>>> William
>>>
>>> On Tue, Jun 30, 2015 at 10:37 AM, William Blevins <wblevins001 at gmail.com
>>> > wrote:
>>>
>>>> I think this is the issue you are describing.
>>>>
>>>> http://scons.tigris.org/issues/show_bug.cgi?id=2980
>>>>
>>>> There is part of a patch attached.  I looked at it at some point, but
>>>> there were still tests failing.
>>>>
>>>> V/R,
>>>> William
>>>>
>>>> On Tue, Jun 30, 2015 at 10:23 AM, Douwe Gelling <douwegelling at gmail.com
>>>> > wrote:
>>>>
>>>>> I have a problem where scons rebuilds files when I change targets on
>>>>> the commandline.
>>>>> I make use of the COMMAND_LINE_TARGETS list to optionally use some
>>>>> other sconsfiles,
>>>>> and also use variant directories to set the object output directories.
>>>>> It seems somehow this
>>>>> may all be interacting with each other.
>>>>>
>>>>> Specifically, I get the following type of behaviour:
>>>>>
>>>>> 1. I build my program using the default target (scons -jN ...)
>>>>>
>>>>> 2. I build some extra program by setting a new target. It depends on
>>>>> some files that were compiled before,
>>>>>     but decides to rebuild it. Using --explain, I get the following
>>>>> type of message:
>>>>>
>>>>> rebuilding 'a/b/c/d.o' because
>>>>>    a/b/c/d.cpp is no longer a dependency
>>>>>    a/b/c/d.cpp is a new dependency
>>>>>
>>>>> 3. I build my default program again, scons rebuilds everything yet
>>>>> again, giving the same message as in 2.
>>>>>
>>>>> I've changes the scons source a bit to show more information in the
>>>>> explain function, and it turns out that
>>>>> in both steps 2 and 3, the file that is no longer a dependency is the
>>>>> original cpp file, and the file that is a
>>>>> new dependency is the file located in the variant directory (say,
>>>>> a/b/c/obj/linux/x86_64/d.cpp).
>>>>>   This happens even though in the call to VariantDir, duplicate is set
>>>>> to 0. If I set it to 1 instead, the message
>>>>> scons gives me is that it's rebuilding 'because the contents of the
>>>>> build action changed'
>>>>>
>>>>>
>>>>> On 30 June 2015 at 15:31, William Blevins <wblevins001 at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> See the Decider section of the man page for how scons determines if a
>>>>>> source has changed.
>>>>>>
>>>>>> SCons also checks for changes to the overall build command as
>>>>>> generated by the executor.
>>>>>>
>>>>>> What is your specific question?
>>>>>>
>>>>>> V/R,
>>>>>> William
>>>>>> On Jun 30, 2015 5:28 AM, "Douwe Gelling" <douwegelling at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> I'm wondering which things scons tracks when deciding whether or not
>>>>>>> to rebuild a file, apart
>>>>>>> from the file itself. I know changing commandline variables forces a
>>>>>>> rebuild, but are there other
>>>>>>> things that do the same? For example, does scons look for changes in
>>>>>>> the environment for a particular file? Or something else?
>>>>>>>
>>>>>>> thanks
>>>>>>>
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