[Scons-dev] SCons performance investigations

[Jason Kenny]

>> After all, there is a very important (in my opinion) distinction to be made between SCons and other build tools like the autotools or CMake:

Just want to second that

Scons, make, ninja, msbuild are items to compare. The idea of comparing CMake, Meson or autotools to SCons in incorrect. There is a big difference in a "generator" and a build system and a build manager (ie stuff like buildbot). I keep hearing how CMake is taking off and everyone is moving to it.... which is really saying it is better cross platform build file generator than automake.

Adding tools to SCons to allow it to "generate" other build system is interesting in cases like MSBuild as it allows user to use the IDE in a way they understand. I think having middleware to allow SCon to better run other build systems is a useful feature to have. 

Jason

-----Original Message-----
From: Scons-dev [mailto:scons-dev-bounces at scons.org] On Behalf Of Dirk Bächle
Sent: Tuesday, July 25, 2017 12:53 PM
To: scons-dev at scons.org
Subject: Re: [Scons-dev] SCons performance investigations

Hi there,


On 21.07.2017 17:39, Andrew C. Morrow wrote:
>
> Hi scons-dev -
>
> The following is a revised draft of an email that I had originally 
> intended to send as a follow up to 
> https://pairlist4.pair.net/pipermail/scons-users/2017-June/006018.html.
> Instead, Bill Deegan and I took some time to expand on my first draft 
> and add some ideas about how to address some of th e issues. We hope 
> to migrate this to the wiki, but wanted to share it here first for 
> feedback.
>
>

and thanks to everyone who contributed to this interesting discussion so far. I'd like to chime in on the topic, but not by delving into "optimization"...you seem to have this working area covered nicely.

Instead I'm very much after somehow connecting all the important points that you brought up, with my own plans about the future of SCons' 
design. I've started to write down how I'd like the core sources to be more flexible, more lightweight and more eligible to things like subclassing and adding new classes or strategies.
What I'd like to propose as the overall strategy is, to not try and make the current "scons" executable to be more versatile. Here I mean "versatile" in the sense that it can be adapted to several different "build project scenarios", such that it will give the maximum of speed or safety in each case.
Rather I'd like to put this "versatility" into the SCons core and its classes. Strengthening the framework character of SCons again by allowing new frontends to be developed more easily.
One of these frontends could be a "scons-lite" (*) for "flat" and large C/C++ projects, where the main task is "compile classes into libs". By simply not supporting "override environments"

     env.Library('foo', Glob('*.cpp'), CPPFLAGS=['-wall','-g'])

we wouldn't have to "subst" so much and build/update times would go down.

This approach would allow us to leave the current "scons" frontend as it is, instead of adding more and more features and command-line arguments to it. This feels just right to me...I probably can't exactly explain why.

Finally, one more comment regarding performance. It's tempting to try and reach the build and update times of other tools like "ninja" and "make", but it's also okay to not fully reach them. We don't have to hide with our project, especially once the "stubprocess" wrapper has been integrated.
After all, there is a very important (in my opinion) distinction to be made between SCons and other build tools like the autotools or CMake: 
the latter two, and a bunch of others, are "Makefile" generators. They allow you to (re)create a build description for your project, that will ensure correct builds as long as the dependencies don't change. But the decision about when you should rerun this generator step is left to the user, which is a disadvantage in my eyes.
Since SCons is reconsidering all dependencies for every build, it's natural that we spend some more time than a "brute-force make". I guess what I'm trying to say here is: let's not over-optimize and by that destroy the "beauty of SCons". ;)

So, once again, I'd like to join the party with my (crazy?) "design ideas". Does this sound interesting, and if yes, how do we organize things to further discuss this?


Best regards,

Dirk


(*) : Naming is hard... :P

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