[Scons-users] SConsignFile(None) + Decider('MD5-timestamp')

[Bill Deegan]

If you don't use SConsignFile(None), then is this still an issue?
Any reason you want a per directory sconsignfile?

On Wed, Aug 12, 2020 at 6:47 AM trevor fitzsimmons <t_fitzs at hotmail.com>
wrote:

> I've dug more into this issue, and have attached a proposed patch against
> scons-4.0.1.
>
> The general idea is to pass the parent node to _build_dependency_map, to
> then correlate "children" to signatures the same way Node/__init__.py
> changed() does, rather than using bsources/etc.  This fixes the pathing
> issues, and should perform the same when building from the same directory
> repeatedly.
>
> Can anyone verify the bug, or provide feedback on the proposed patch?
>
> Should I open a bug report instead?
>
> Thanks,
> Trevor
>
> ------------------------------
> *From:* Scons-users <scons-users-bounces at scons.org> on behalf of trevor
> fitzsimmons <t_fitzs at hotmail.com>
> *Sent:* Wednesday, July 29, 2020 11:52 AM
> *To:* scons-users at scons.org <scons-users at scons.org>
> *Subject:* [Scons-users] SConsignFile(None) + Decider('MD5-timestamp')
>
> Since scons-3.0.2 (through the current scons-4.0.1), using
> SConsignFile(None) in conjunction with Decider('MD5-timestamp') causes
> scons to rebuild targets when invoked from different directories in the
> source code hierarchy.
>
> Attached is a simple example to illustrate the issue.  Building from
> test/src will cause an initial build as expecting.  Building again from
> test/src will do nothing, as expected, and report everything is
> up-to-date.  However, if you build from test, everything in test/src will
> be rebuilt, even though it is already up-to-date.  Building again from test
> will do nothing, as expected, and report everything is up-to-date.
> Building from test/src will then cause another full rebuild, even though
> everything is up-to-date, and the cycle continues.
>
> This has something to do with the dependency_map which was added in
> Node/FS.py in scons-3.0.2, but I do not know enough about the inner
> workings of scons to propose a fix.  FS.py
> changed_timestamp_then_content(self, target, prev_ni, node=None) calls
> prev_ni = self._get_previous_signatures(dependency_map).  Depending on the
> starting directory, self is either main.cpp or src/main.cpp, while the key
> in dependency_map is the other.
>
> In our full code-base, it's quite usual to build in a subdirectory while
> changing code, to avoid waiting on a full build, so the current work-around
> is to not use Decider('MD5-timestamp').  It would be ideal to have a patch
> that could eventually be applied to scons, to fix the issue in a future
> version.
>
> Thanks
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