compiler, runtime: enable go:wasmexport for wasip2 #4496
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aykevl
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Oct 5, 2024
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| wasi_run.Exports.Run = func() cm.BoolResult { | ||
| callMain() | ||
| return false | ||
| } |
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Interesting, any reason not to use //export here?
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Great question! All exports defined in WIT should use //go:wasmexport, including the wiring up from wasi:cli/command#run to main.main. This is the standard pattern for wiring up exports generated from wit-bindgen-go.
- Developer generates Go (e.g.
wasi:http/proxy) - Developer writes Go library that wraps the low-level APIs in the generated code (e.g. a
net/httpcompatible shim) - In the shim code, developer assigns the relevant
Exportsstruct field to their implementation. For example: https://github.com/ydnar/wasi-http-go/blob/76673aea4c888a0e9b36d20604b3f11a4831bdd8/wasihttp/server.go#L21-L24
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FWIW, I believe //export should still be used for cabi_realloc since the Component Model defines different reentrancy rules for low-level exports like this.
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This builds on #4451 to enable
//go:wasmexportforwasip2(WASI Preview 2).//go:wasmexportis now permitted and supersedes//go:exportand//exportif both are present.wasip2target now defaults to-buildmode=c-shared, since all WASI 0.2+ programs are reactors.main.mainis called by thewasi:cli/run#runexport in awasmexport.