[Scons-users] Need help debugging my build

[Dirk Bächle]

Hi Gottfried (Moin!),

On 04.06.2015 16:31, Ganssauge, Gottfried wrote:
> My build – which is somewhat large – normally runs fine using scons-local-2.3.4 with python2.7.6 on Ubuntu Linux-14.04
> But when I’m starting the same build twice in a row I’d expect it to rebuild nothing at all the second time through.
> The actual targets which I request aren’t rebuilt in fact but some intermediate targets.

what happens when you rebuild the same target a third time? Is the output as you'd expect in run #3?
Then, you can try to disable the implicit command dependency mechanism with

   env['IMPLICIT_COMMAND_DEPENDENCIES'] = False

and see if it helps.
The underlying problem is, that SCons stores the list of dependencies (and its checksums) as ordered list (=vector, not dict). In 
your use case the number of children and their checksums stay the same...but their order changes from one run to the other. This may 
happen especially for files that get created during a build, because they get found earlier or later then while scanning folders for 
dependencies...depending on whether they already exist, how search paths are set, and how the implicit dependency graph is traversed.

Best regards,

Dirk