Working Directory Changes
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Working Directory Changes
 
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Hi all,
I'd like to push a really core change in file management: the working directory. This is really needed for command line apps, when you have your app deployed in some directory and you're launching it from another one. The current implementation, where workingDirectory = imageDirectory, forces to have absolute paths or extra handling all over the place to manage this complexity. Rajula proposed a couple of months ago a solution for this based on the getcwd functions. You can read in his blogpost why using getcwd is better than $PWD in general here: Now, since accessing the working directory is a core part of Pharo but based on UFFI, his implementation was breaking the build process. We cannot and we will not integrate UFFI in the bootstrap because it depends mainly on the compiler which is a big beast. Instead, I propose that only for this core-core-core feature, we use directly FFI. In other words, the bootstrap will include just a couple of classes to manage the basics of FFI. And the working directory will be fetched by using this low level API. Such a call looks like this: (ExternalLibraryFunction name: 'getcwd' module: 'libc.dylib' callType: 1 returnType: ExternalType char asPointerType argumentTypes: { ExternalType char asPointerType. ExternalType long }) invokeWith: buffer with: bufferSize. We reviewed it with Pablo two days ago. The build process works with this implementation and tests are still running. The pull request is in here: Thanks, Guille, Pablo and Rajula
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Re: Working Directory Changes
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From my experiments to execute FFI calls without FFI packages in the image I know that we can do it without it on even lower level but then we will anyway need to somehow handle library paths and so on. So to add these small packages into the bootstrapped kernel is totally reasonable and will open a lot of next possibilities. So definitely yes! Cheers, -- Pavel 2017-10-11 10:27 GMT+02:00 Guillermo Polito <[hidden email]>:
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Re: Working Directory Changes
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Re: Working Directory Changes
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In reply to this post by Guillermo Polito
in general, this core-core functions is better to implement them as primitives.
and you put a fallback using UFFI (in case the primitive is not there).
of course, your solution works… but it adds dependency with FFI-Kernel, which is also not good to have it in the bootstrap IMO. take a look at OSEnvironment>>getEnv implementation. we can go that direction and I think it will be better. Esteban
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Re: Working Directory Changes
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Re: Working Directory Changes
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Re: Working Directory Changes
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In reply to this post by Guillermo Polito
Hi Guille, I think some time ago we discussed exactly this or at least very similar [1]. AFAIR, we didn't arrive to an agreement. Or maybe we did but I was never able to implement it, I don't remember. But I would appreciate if you can at least read the discussion to see if there is something worth considering with your new changes. Cheers, On Wed, Oct 11, 2017 at 5:27 AM, Guillermo Polito <[hidden email]> wrote:
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Re: Working Directory Changes
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In reply to this post by EstebanLM
2017-10-11 10:54 GMT+02:00 Esteban Lorenzano <[hidden email]>:
+1 for new primitive. Because instead any new platform will require implemented FFI which is not easy.
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Re: Working Directory Changes
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Re: Working Directory Changes
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Re: Working Directory Changes
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Hi all, Now I had some minutes to take a further look at this. ** Mariano, yes, I remember that conversation. What we propose is aligned to that: FileSystem workingDirectory shouldBe == getcwd And **almost always** FileSystem workingDirectory shouldBe == $PWD This is because the real working directory is the one held by the process. $PWD is managed by bash and it can get out of sync with getcwd. For more info take a look at rajula's blogpost in the first email. ** About security, I don't really buy the argument. - There are many aspects of security: internal in the image, external. FFI is not the only thing to *care about* - right now we can do stuff like - FileSystem root ensureDeleteAll (and given pharo started with sudo...) - nil become: true - OpalCompiler compile: 'someMethodThatOverriddenBreaksEverything ...' - FFI plugin is shipped with the VM - so removing FFI support is as easy as removing the plugin - but this means that even if that FFI support is not in the image, any piece of code can do: - Myclass compile: 'test Metacello install: ''FFI''; please'; test. - or create a method calling the FFI primitives This does not mean I don't think about security, but I believe it should be managed in some other way. A security solution for real needs to manage reflection as well as external resources, and control how dependencies and packages are loaded. Because, moreover, I believe that while you may want to forbid FFI calls in some part of your app, you may want that some other parts of the system can use FFI. ** About modularity. But I'm sure I'm one of the guys that cares the most about modularity and cries aloud every time we introduce bad dependencies. Now, I'm proposing the introduction of FFI because I think its manageable and it's being controlled. It does not affect the bootstrap, and I don't think it will forbid us to get even smaller kernels. ** The most important argument, that at least I did not see anybody complain about, is backwards compatibility. This implementation may break backwards compatibility, because this does not hold anymore: FileSystem imageDirectory == FileSystem workingDirectory Well, yes, it holds if you start your vm/image from the same directory where the image is located. Which is what most users do. ** I also talked with Esteban about his reasons. His concern was about consistency. If you take a look at how getEnv is resolved: getEnv: varName "This method calls the Standard C Library getenv() function." "OSEnvironment current getEnv: 'HOME' " <primitive: 'primitiveGetenv' module: '' error: ec> ec ifNil: [ ^self getEnvViaFFI: varName ]. ec == #'bad argument' ifTrue: [ varName isString ifFalse: [ ^self getEnv: varName asString ] ]. self primitiveFail If first tries to call a primitive and then, as fallback, it calls FFI by default. I changed the pull request to do the same thing about the working directory. That way, as soon as we have implemented the primitive, that will be in usage instead of the FFI call. Guille On Wed, Oct 11, 2017 at 3:07 PM, Denis Kudriashov <[hidden email]> wrote:
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Re: Working Directory Changes
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