[Scons-users] What affects rebuilding?

[Douwe Gelling]

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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