[Haskell-cafe] Files and Modules

[Brandon Allbery]

As long as we're using system tools for assembling and linking, we must
abide by their constraints. Not using them isn't really viable; linking in
particular is a nightmare. The bytecode interpreter has a partial linker
because it can't use the system one, and it's easily the nastiest part of
ghc. It's also completely nonportable, by definition: every target has its
own notion of what relocations are available and how they work.

On Mon, Dec 2, 2024 at 4:16 AM julian getcontented.com.au <
julian at getcontented.com.au> wrote:

> In a recent project that compiles Haskell source from data (ie of type
> Text from the module Data.Text), it would be useful to be able to decouple
> the dependency between GHC’s notion of where modules are and the file
> system. This doesn’t seem to be programmatically controllable.
>
> How tenable is this? Would it be useful for anyone else to have
> compilation itself be more first class in the language? If I think about
> languages such as LISP/Racket/Clojure, there’s a certain flexibility there
> that Haskell lacks, but it’s not apparent why, other than historical
> reasons? Would this imply changing compiling and linking into a different
> Monad than IO?
>
> At the moment to compile some source that exists in Text, my system has to
> write a bunch of temp files including the Text that contains the main
> module, and then put other modules in directories named a certain way, run
> the compiler across them via some exec command to call GHC or stack
> externally, then read the resulting executable back off disk to store it in
> its final destination.
>
> It might be useful to be able to do this from within Haskell code
> directly, partly similarly to how the hint library works. Though, in this
> case it would almost certainly also require being able to have two versions
> of GHC loaded at once, which would also imply being able to simultaneously
> have multiple or different versions of libraries loaded at once, too, and
> possibly also just from data, ie not from disk. It feels like a massive,
> massive project at that point, though, like we’d be putting an entire
> dependency system into a first-class programmable context. I’m still
> interested in what folks think about these ideas, though, event though we
> this may never eventuate.
>
> Does it seem to anyone else like abstracting the library and module-access
> capabilities of compilation so that it’s polymorphic over where it gets its
> data from might be useful? Is this just ridiculous? Does this step into
> Backpack's territory? From memory, the Haskell report doesn’t specify that
> modules necessarily need to be tied to the file system, but I think GHC
> imposes one file per module and that it be one the FS.
>
> Julian
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-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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