[Scons-users] find new targets from other targets?

[Scott Johnson]

If I understand you correctly, that means that every time I run a clean build via Scons I have to run every file through Jinja once to find all the targets, then a second time through Jinja to build the outputs. Even an incremental build will have to run every file through Jinja once before it discovers that there’s nothing to rebuild.

At that point what does Scons buy me versus a simple Python script that builds all files every time? With a script, clean builds will be faster and incremental builds will be no slower.



> On Feb 24, 2020, at 7:33 AM, Bill Deegan <bill at baddogconsulting.com> wrote:
> 
> Actually if your scanner reading the jinja source files can navigate the jinja if's then you don't need to produce the files before you know what files it depends on.
> 
> (not that different from c preprocessors #ifdef..)
> 
> On Sun, Feb 23, 2020 at 10:31 PM Scott Johnson <scott.johnson at arilinc.com <mailto:scott.johnson at arilinc.com>> wrote:
> Yes, evaluating the if's is what Jinja does, and that's how the source file gets processed into the target file.
> 
> So I need to build the target, then I can parse the target to find additional targets that I need to also build.
> 
> I will have some other mechanisms too, not only Jinja, for building these files, but each of the targets will need to be parsed after being built.
> 
> 
> On Fri, Feb 21, 2020 at 2:11 PM Bill Deegan <bill at baddogconsulting.com <mailto:bill at baddogconsulting.com>> wrote:
> Scott,
> 
> I'm not sure based on your example how all the files which need to be processed wouldn't be known before you ran SCons.
> 
> if top.F.jinja is the following (and is the top file which ends up including all the others)
> 
> tgt1.v
> -F pkg1.F
> {% if some_condition %}
> -F pkg2.F
> {% endif %}
> 
> And "-F" is the include statement. Then all you'd need is the way to evaluate the {% if's %} to know which files it includes.
> 
> -Bill
> 
> On Thu, Feb 20, 2020 at 10:05 PM Scott Johnson <scott.johnson at arilinc.com <mailto:scott.johnson at arilinc.com>> wrote:
> 
>> On Feb 20, 2020, at 6:46 PM, Bill Deegan <bill at baddogconsulting.com <mailto:bill at baddogconsulting.com>> wrote:
>> 
>> Yes. set it as src_scanner. 
>> 
>> You're scanner doesn't return any nodes... 
>> 
> 
> It doesn’t yet, as this is just an experimental toy, but see my original post. I can’t determine what else needs to be built until after the first target is built. And unlike this toy example, the real target isn’t just a simple copy of the source file. So scanning the source file won’t work for me.
> 
> A traditional scanner looks at the source file and finds dependencies that need to be built before this source file is processed. My use case is different. I need to process the source file, then look at the target file and find new (independent) files to build.
> 
> I found this question on Stack Overflow that suggests that what I’m trying to do is either tricky or impossible, depending on which answer you believe.
> 
> https://stackoverflow.com/questions/24671859/scons-how-to-generate-dependencies-after-some-targets-have-been-built/26302284 <https://stackoverflow.com/questions/24671859/scons-how-to-generate-dependencies-after-some-targets-have-been-built/26302284>
> 
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