IMPORTED_TABLE setting to import function pointer table?

[hoodmane]

Could we add an -sIMPORTED_TABLE setting?

Since -sRELOCATABLE is no longer the default, I've been getting problems with this code:
https://github.com/python/cpython/blob/main/Python/emscripten_trampoline.c#L35
because wasmTable and wasmMemory are undefined. Here I want to define an import via a separate wasm module so that we can use a fall back if wasm-gc is not supported. That module needs the table and the memory. I want to use it as a direct import, so I need to compile the other wasm module before the main wasm module is compiled. Thus, it needs both the table and the memory to be imported. I can force the memory to be imported with -sIMPORTED_MEMORY, but I need a separate setting for the table.

[sbc100]

I assume you are talking about an dynamically linked application since you mention "-sRELOCATABLE is no longer the default"?

I agree it could likely make sense to add IMPORTED_TABLE to match IMPORTED_MEMORY.

However, as always we try to resist adding new settings until we really need to since each new setting adds a significant testing and maintenance overhead. Maybe if we could understand you use case a little better in order to justify the new setting? i.e. maybe we can document the type of users like yourself who might need this setting.

It sounds like the use case is that the memory and/or table need to be used in other modules before the main module is instantiated, is that right? Is that the main driver here? And the reason you can't instantiate the main module first in order to get the memory and the table is that you want to provide direct imports to the main module. Would a level indirection therefore also fix your issue?

[hoodmane]

Yeah we are passing -sMAIN_MODULE.

A level of indirection could fix the issue. I was concerned that it would add some additional complexity and perform worse -- this call is very hot. But perhaps a call_indirect to always the same function will be as efficient as a direct call after JIT. If this is the case then we probably don't need this setting.

[hoodmane]

I opened #26228 so we can see what adding the setting looks like. But we can just close it if you think I should go the other way. It feels to me that if there is going to be an -sIMPORTED_MEMORY there should also be an -sIMPORTED_TABLE but that's just my opinon.

[sbc100]

That does sounds reasonable yes.