function Wasm.instantiate

def Wasm.instantiate(
path: str,
/,
*,
args: list[str] = [],
env: dict[str, str] = …,
preopened_dirs: dict[str, str] = …,
inherit_stdio: bool = True,
imports: dict[str, dict[str, typing.Any]] = …
) -> Instance

Instantiate a WASM module with optional WASI configuration and host function imports.

Example

# In host_funcs.axl:
def get_term_size(ctx, memory) -> tuple[int, int]:
    return (80, 24)

# In main.axl:
load("./host_funcs.axl", "get_term_size")

instance = ctx.wasm.instantiate(
    "app.wasm",
    args = ["--verbose"],
    env = {"HOME": "/home/user"},
    preopened_dirs = {"/tmp": "/sandbox"},
    imports = {
        "env": {
            "get_term_size": get_term_size,
        }
    },
)
instance.start()  # Call _start for WASI modules
result = instance.exports.my_function(42)

Host Function Signature

Host functions receive two injected arguments followed by WASM arguments:

ctx - Task context (currently None, reserved for future use)
memory - WASM memory access (currently None, reserved for future use)
Additional arguments correspond to the WASM function signature

Return values are converted back to WASM types. Use tuples for multi-value returns. Parameters

path: - Path to the WASM binary file
args: - Command-line arguments to pass to the WASM module (WASI)
env: - Environment variables to set for the WASM module (WASI)
preopened_dirs: - Directories to pre-open for filesystem access (WASI). Keys are host paths, values are guest paths.
inherit_stdio: - Whether to inherit stdin/stdout/stderr from the host (default: true)
imports: - Host function imports, organized by module name and function name. Important: Host functions must be imported from a loaded module via load(), not defined in the same file. This ensures they are frozen and can be safely stored in the WASM runtime.

​Example

​Host Function Signature

Example

Host Function Signature