wazero

Files

Crypt Keeper 57a705e594 Disallows nil context and fixes linters (#754 )

staticcheck linters broke until recent golangci-lint. Now, normal
behaviour of enforcing no nil context works again. Ex.
```
assemblyscript/assemblyscript_example_test.go:16:25: SA1012: do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use (staticcheck)
	r := wazero.NewRuntime(nil)
```

Since default lint already checks for nil context, this removes our
permission of nil context args. The original reason we permitted nil is
no longer valid: we once allowed context to be stashed in config, and
removed that as it caused bugs. We forgot to undo allowing nil
explicitly.

Note: this doesn't particularly check in our code for nil context,
similar as we don't particularly check in our code for nil anything
else. End users should use linters as none of our parameters should be
nil anyway.

Signed-off-by: Adrian Cole <adrian@tetrate.io>

2022-08-19 14:52:50 +08:00

testdata

Disallows nil context and fixes linters (#754 )

2022-08-19 14:52:50 +08:00

cat_test.go

examples: adds rust build and WASI example (#676 )

2022-07-08 10:49:50 +08:00

cat.go

Disallows nil context and fixes linters (#754 )

2022-08-19 14:52:50 +08:00

README.md

example(wasi): fixes link drifts (#679 )

2022-07-11 07:33:41 +08:00

README.md

WASI example

This example shows how to use I/O in your WebAssembly modules using WASI (WebAssembly System Interface).

$ go run cat.go /test.txt
greet filesystem

If you do not set the environment variable TOOLCHAIN, main defaults to use Wasm built with "tinygo". Here are the included examples:

cargo-wasi - Built via cargo wasi build --release; mv ./target/wasm32-wasi/release/cat.wasm .
tinygo - Built via tinygo build -o cat.wasm -scheduler=none --no-debug -target=wasi cat.go
zig-cc - Built via zig cc cat.c -o cat.wasm --target=wasm32-wasi -O3

Ex. To run the same example with zig-cc:

$ TOOLCHAIN=zig-cc go run cat.go /test.txt
greet filesystem

Toolchain notes

Examples here check in the resulting binary, as doing so removes a potentially expensive toolchain setup. This means we have to be careful how wasm is built, so that the repository doesn't bloat (ex more bandwidth for git clone).

While WASI attempts to be portable, there are no specification tests and some compilers partially implement features. Notes about portability follow.

cargo-wasi (Rustlang)

The [Rustlang source][testdata/cargo-wasi] uses cargo-wasi because the normal release target wasm32-wasi results in almost 2MB, which is too large to check into our source tree.

Concretely, if you use cargo build --target wasm32-wasi --release, the binary ./target/wasm32-wasi/release/cat.wasm is over 1.9MB. One explanation for this bloat is wasm32-wasi target is not pure rust. As that issue is over two years old, it is unlikely to change. This means the only way to create smaller wasm is via optimization.

The cargo-wasi crate includes many optimizations in its release target, including wasm-opt, a part of binaryen. cargo wasi build --release generates 82KB of wasm, which is small enough to check in.

emscripten

Emscripten is not included as we cannot create a cat program without using custom filesystem code. Emscripten only supports WASI I/O for stdin/stdout/stderr and suggest using wasi-libc instead. This is used in the zig-cc example.