Tim Schaub created ARROW-17584:
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Summary: [Go] Unable to build with tinygo
Key: ARROW-17584
URL: https://issues.apache.org/jira/browse/ARROW-17584
Project: Apache Arrow
Issue Type: Bug
Components: Go
Reporter: Tim Schaub
I was hoping to use TinyGo to build WASM binaries with Arrow. TinyGo can
generate builds that are [1% the
size|https://tinygo.org/getting-started/overview/#:~:text=The%20only%20difference%20here%2C%20is,used%2C%20and%20the%20associated%20runtime.&text=In%20this%20case%20the%20Go,size%20(251k%20before%20stripping)!]
of those generated with Go (significant for applications hosted on the web).
Arrow's use of `reflect.SliceHeader` fields limits the portability of the code.
For example, the `Len` and `Cap` fields are assumed to be `int` here:
https://github.com/apache/arrow/blob/go/v9.0.0/go/arrow/bitutil/bitutil.go#L158-L159
Go's [reflect package
warns|https://github.com/golang/go/blob/go1.19/src/reflect/value.go#L2675-L2685]
that the SliceHeader "cannot be used safely or portably and its representation
may change in a later release."
Attempts to build a WASM binary using the github.com/apache/arrow/go/v10 module
result in failures like this:
{code}
tinygo build -tags noasm -o test.wasm ./main.go
{code}
{code}
# github.com/apache/arrow/go/v10/arrow/bitutil
../../go/pkg/mod/github.com/apache/arrow/go/v10@v10.0.0-20220831082949-cf27001da088/arrow/bitutil/bitutil.go:158:10:
invalid operation: h.Len / uint64SizeBytes (mismatched types uintptr and int)
../../go/pkg/mod/github.com/apache/arrow/go/v10@v10.0.0-20220831082949-cf27001da088/arrow/bitutil/bitutil.go:159:10:
invalid operation: h.Cap / uint64SizeBytes (mismatched types uintptr and int)
{code}
This happens because TinyGo uses `uintptr` for the corresponding types:
https://github.com/tinygo-org/tinygo/blob/v0.25.0/src/reflect/value.go#L773-L777
This feels like an issue with TinyGo, and it has been ticketed there multiple
times (see https://github.com/tinygo-org/tinygo/issues/1284). They lean on the
warnings in the Go sources that use of the SliceHeader fields makes code
unportable and suggest changes to the libraries that do not heed this warning.
I don't have a suggested fix or alternative for Arrow's use of SliceHeader
fields, but I'm wondering if there would be willingness on the part of this
package to make WASM builds work with TinyGo. Perhaps the TinyGo authors could
also offer suggested changes.
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