Warn if EXPORTED_FUNCTIONS is used with MAIN_MODULE=1/SIDE_MODULE=1

[sbc100]

This doesn't make sense since these imply all functionm are to be
exported.

The test code changes here are just to use @paramaterized.

[Akaricchi]

Why is this an error? It seems quite benign and warrants a warning at most, IMO.

[kripken]

I agree with @Akaricchi that this could be a warning. Perhaps an error in strict mode?

Another thought, the list of exported functions is checked against to see if they exist in the output (or we warn with something like "asked to export foo() but it doesn't exist"). That might still be useful for static linking?

[sbc100]

OK, I'll make it warning.

We already do use this for static linking to drive the "undefined function" error reporting.

[sbc100]

I think it warrants being at least a warning because its usage normally show a misunderstanding on the part of the user as to how MAIN_MODULE=1 and SIDE_MODULE=1 actually work.

[sbc100]

This kind of check also also helps developers like us to understand the codebase better. It certainly helps me reason about the meaning of EXPORTED_FUNCTIONS + SIDE_MODULE... without this change I would need to do bunch of experiments and reason to figure it out. After this change its super obvious.

This is why i'm so keen to adding working when options are used that are not compatible, rather than silently accepting the bad combination.

[kripken]

Yeah, I agree it's good to warn about stuff like this, good idea.

[kripken]

I understand it's ok to put standalone wasm in the else of LINKABLE, as we don't support linking with that mode. And exported_functions is ok to put in that else because it isn't needed when linkable. However, I'm not sure what this __data_end thing is?

[sbc100]

Basically because LINKABLE added --export-all there is no point in having any --export= flag individually. Its redundant to export all then then also export something individually in wasm-ld.

It is more link:

if exporting_everthing:
   add_export_all
else:
   add_export_specific

[sbc100]

Actually I think I should hold off landing this until we figure out how we want exporting to work with dynamic linking. See #10079

[stale]

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