[Scons-users] What affects rebuilding?

[William Blevins]

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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>
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