How to generate standalone binary from .wasmu file

[darccio]

Summary

By default, it seems that wasmer compile generates a .wasmu file. According to #3014 (comment), it's already contains compiled machine instructions for the target arch.

From the same thread, it seems implied that using create-exe with a .wasmu should generate a standalone binary with Wasmer runtime embedded on it and the module converted and linked as object. This would seem to align with a old blog post in wasmer.io.

When I run the following instructions, I get an error about a bad magic number.

> wasmer compile hello_world.wat -o hello_world.wasmu # Find hello_world.wat in the Additional details section.
Compiler: cranelift
Target: x86_64-unknown-linux-gnu
✔ File compiled successfully to `hello_world.wasmu`.

> wasmer create-exe hello_world.wasmu -o hello_world
Compiler: cranelift
Target: x86_64-unknown-linux-gnu
Using path `/home/dario/.wasmer/cache/wasmer-linux-amd64/lib/libwasmer-headless.a` as libwasmer path.
error: Compilation error: WebAssembly translation error: Invalid input WebAssembly code at offset 0: magic header not detected: bad magic number - expected=[
    0x0,
    0x61,
    0x73,
    0x6d,
] actual=[
    0x77,
    0x61,
    0x73,
    0x6d,
]

Does create-exe supports compile output files or should we use another tool to generate a .wasm file - like wat2wasm - to feed it to create-exe?

Thanks!

Additional details

Wasmer version: wasmer 5.0.4

hello-world.wat:

(module
  ;; Import the required WASI functions
  (import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))

  ;; Define a buffer to store the message
  (memory (export "memory") 1)
  (data (i32.const 8) "Hello, World!\n")

  ;; Define the _start function
  (func $main (export "_start")
    ;; Setup the iovec array
    (i32.store (i32.const 0) (i32.const 8))    ;; pointer to the message
    (i32.store (i32.const 4) (i32.const 14))   ;; length of the message

    ;; Call fd_write
    (call $fd_write
      (i32.const 1)  ;; file_descriptor - 1 for stdout
      (i32.const 0)  ;; *iovs - pointer to the iovec array
      (i32.const 1)  ;; iovs_len - number of iovec entries
      (i32.const 20) ;; nwritten - where to store the number of bytes written
    )
    drop ;; Discard the result
  )
)

[darccio]

Update: I converted the .wat file using wat2wasm and create-exe didn't complain but running the binary failed with a reference to wasmer-universal:

> wasmer create-exe hello_world.wasm -o hello_world
Compiler: cranelift
Target: x86_64-unknown-linux-gnu
Using path `/home/dario/.wasmer/cache/wasmer-linux-amd64/lib/libwasmer-headless.a` as libwasmer path.
✔ Native executable compiled successfully to `hello_world`.
> ./hello_world 
Failed to create module from atom "hello_world"
Error len: `65`
incompatible binary: The provided bytes are not wasmer-universal

This makes sense if create-exe only works with WASM Universal binaries.

[xdoardo]

Hello, thanks for the report. I'll investigate this as soon as possible.

[xdoardo]

Currently, create-exe only supports receiving .wasm files, but we can investigate how to make it happen.

[darccio]

Thanks @xdoardo. As I showed in #5422 (comment), using a .wasm returns an error mentioning bytes not being wasmer-universal.

What am I missing? I'd appreciate some orientation.