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

[Esteban Lorenzano]

I wasn't aware of that discussion, but I'm still disagree with their conclusions. 
I'm certain that sources must be versioned. But sources are: VMMaker + configuration + platform files... generated files are not sources and to keep them in source tree is prone to error. 
That's my feeling about this... anyway, I'm also not sure about re-discuss this :P

best,
Esteban


El 11/03/2011, a las 8:50a.m., Frank Shearar escribió:

> We've had this discussion before, in November last year - "VM packaging for Cog transition" - starting here: http://lists.squeakfoundation.org/pipermail/vm-dev/2010-November/005797.html
> 
> frank
> 
> On 2011/03/11 11:34, Esteban Lorenzano wrote:
>> 
>> 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.
>> 
>> 
>> 
>