Implement -fexternal-interpreter via static linking

An interesting idea from @hvr. When using -fexternal-interpreter, we can statically link the required packages and object files into a new iserv binary, and use that as our external interpreter.

This would mean we could support TH and even limited GHCi without needing a dynamic linker of any kind, which is extremely cool. Apparently this would be useful for AIX where doing dynamic linking is hard.

changed milestone to %8.2.1

changed weight to 5

added Ttask Trac import labels

changed the description

changed milestone to %8.4.1

It doesn't look like this will happen for 8.2.

changed milestone to %8.6.1

This ticket won't be resolved in 8.4; remilestoning for 8.6. Do holler if you are affected by this or would otherwise like to work on it.

Removing milestone as no one is currently actively working on this.

This seems like an interesting idea. Could anyone outline the necessary steps that someone would need to take to implement it?

added GHCi Tfeature request linking remote GHCi labels

1. Figure out how a user would produce a statically linked iserv binary of their own (presumably iserv-as-a-library of some kind). Maybe make this automatic somehow - when iserv is required to evaluate some TH, the compiler knows which packages it requires, so it can kick off a link step to build the static iserv binary and then invoke it.
2. Figure out how to get the addresses of the symbols in the static binary. Perhaps using -export-dynamic.

That's all the springs to mind, there might be other wrinkles I haven't thought of.

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Maybe make this automatic somehow - when iserv is required to evaluate some TH, the compiler knows which packages it requires, so it can kick off a link step to build the static iserv binary and then invoke it.

That's exactly what we do for the JS interpreter (!9779 (closed)). Doing this for other targets would simplify the external interpreter: no need to build nor distribute iserv-* binaries anymore.

mentioned in issue #24731