[Vm-dev] Rant about generated files: should they stay in repository?

[Esteban Lorenzano]

Igor, I'm with you :)
let's get rid of generated sources from repository!

best,
Esteban

El 10/03/2011, a las 10:01p.m., Igor Stasenko escribió:

> 
> I am against it , because it is going to nowhere.
> 
> So let me elaborate...
> 
> In Cog, we have an image which generating an universal sources for VM
> on all platforms.
> These generated files then put under source control.
> 
> Pros:
> - to build VM you can just checkout and build
> 
> Cons:
> - err , wait.. which exactly VM you going to build? can you use same
> sources for different builds?
> 
> Yes, I can use same generated sources for everything, but depending on
> configuration and/or target operating system i can receive completely
> different results.
> 
> Because, for recreating VM as an artifact to reproduce same
> circumstances as they were (when some bug was triggered) a generated
> sources snapshot is not enough.
> 
> Simple example:
>  - VM compiled for Macs using -O3 optimization are stable.
> In contrary to linux, where using -O2 with certain files makes your
> VM crash few (milli)seconds after startup.
> 
> Second ( i don't like repeating myself but still ;):
> - the only way to make sure that VMMaker loads into our latest and
> greatest image(s) and producing same output(s) is to have someone to
> continuously try load it,
> then use it to generate sources, then compile the VM and then run
> tests for that VM.
> We have a generous guys in our community, who can do that for us. This
> is a Mr Hudson, and Mr Jenkins that joined party lately.
> 
> I'd like to stress that generated files are just an intermediate data,
> which nobody interested in.
> 
> Because as input what is relevant should be only :
> - a VMMaker
> - a platform-specific sources/libs
> - a build configuration
> 
> and as output we always have:
>  - VM
> 
> what happens in the middle is really unimportant as long as you can
> guarantee reproducibility of  the same output from same inputs.
> 
> VM functioning should not depend on some random noise which comes from
> unrelated sources like
> - generated source files line ending convention
> - the date stamp when VM was built
> - anything which is not listed in the inputs list above
> and if it does, we should eliminate it.
> 
> Because if it does, then you don't have a stable builds. And having a
> snapshot of sources which kinda works and kinda stable
> worth nothing, because at any moment in ongoing development you can
> meet same issue which will pop up out of nowhere.
> And it will pop out exactly because you don't care to always do things
> from scratch , starting from image and VMMaker.
> Because it is so convenient to just pull the generated sources from
> repo and you done.
> And those silly stupids which trying to use VMMaker are not of your
> concern.. because when they fail to build stable VM (and they will),
> you can always tell them that they are using wrong sources and because
> you can't reproduce it (things is always working well for you, in your
> warm corner :)
> 
> So, i think that keeping a generated files works as some kind of
> defensive policy which doesn't allows you to address certain
> problems for real.
> And sure thing, because we are lazy :)
> 
> 
> -- 
> Best regards,
> Igor Stasenko AKA sig.