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

[trevor fitzsimmons]

Sorry, somehow this email ended up in junk & I didn't see it when replying to the other one.

The goal is to be able to build from any directory, and only have necessary targets rebuilt.  SConsignFile(None) seemed to be the only option I could find to do this.

The example was simplified.  The real project has many nested directories, libraries, programs, etc.  Typically, builds are run from the top level, to build all changes (like when pulling changes from other developers).  However, it's also very helpful to be able to build from a specific directory when writing code (perhaps a single library, or a set of relate libraries), to avoid waiting on a full rebuild.

Is there another setup that accomplishes this?  Maybe I just need to restructure things.

________________________________
From: Scons-users <scons-users-bounces at scons.org> on behalf of Bill Deegan <bill at baddogconsulting.com>
Sent: Wednesday, August 12, 2020 10:22 PM
To: SCons users mailing list <scons-users at scons.org>
Subject: Re: [Scons-users] SConsignFile(None) + Decider('MD5-timestamp')

So your use model is not strictly supported.
You have directories with a bunch of SConstructs in them and SConsignFile(None) so it dumps a file in every source dir.
All files stored in such are relative to the invocation directory.
In essence you have a number of independent build systems which happen to call each other thus yielding file paths which are different when you invoke from different dirs and thus the rebuilds.

There's actually no reason to do this if your only goal is to be able to launch the build from any source directory.
Is that your goal?
Or something else?
Please explain.

Thanks,
Bill

Or are you trying something else?

On Wed, Aug 12, 2020 at 5:43 PM Bill Deegan <bill at baddogconsulting.com<mailto:bill at baddogconsulting.com>> wrote:
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<mailto: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<mailto:scons-users-bounces at scons.org>> on behalf of trevor fitzsimmons <t_fitzs at hotmail.com<mailto:t_fitzs at hotmail.com>>
Sent: Wednesday, July 29, 2020 11:52 AM
To: scons-users at scons.org<mailto:scons-users at scons.org> <scons-users at scons.org<mailto: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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