Compiler error on call_indirect/function pointer

[dsyer]

> asc assembly/index.ts --target debug


▌ Whoops, the AssemblyScript compiler has crashed during buildJS :-(
▌ 
▌ Here is the stack trace hinting at the problem, perhaps it's useful?
▌ 
▌ /home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/std/portable/index.js:200
▌     throw new AssertionError(message);
▌           ^
▌ 
▌ AssertionError: assertion failed
▌     at null.Q.assert (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/std/portable/index.js:200:11)
▌     at er.makeLowerToValue (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/js.ts:1020:21)
▌     at er.visitFunction (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/js.ts:390:16)
▌     at er.visitFunctionInstances (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/util.ts:132:53)
▌     at er.visitElement (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/util.ts:91:14)
▌     at er.visitFile (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/util.ts:59:14)
▌     at er.walk (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/util.ts:47:65)
▌     at er.build (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/js.ts:616:10)
▌     at Function.build (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/bindings/js.ts:99:40)
▌     at Module.mS (/home/dsyer/dev/scratch/hello-as/node_modules/assemblyscript/src/index-wasm.ts:335:20)
▌ 
▌ If you see where the error is, feel free to send us a pull request. If not,
▌ please let us know: https://github.com/AssemblyScript/assemblyscript/issues
▌ 
▌ Thank you!

Simple program to reproduce:

@external("env", "console.log")
declare function print(s: i32): void

function increment(input: i32): i32 {
  return input + 1;
}

export function callback(fn: (input: i32) => i32, input: i32): i32 {
  return fn(input);
}

export function call(input: i32): i32 {
  return callback(increment, input);
}

[MaxGraey]

Yeah. It looks like binding generator doesn't support functions as argument during codegen.

[MaxGraey]

For now can you could just remove export for callback if this possible?

[dsyer]

Yes, that works for the simple repro above. It's not possible in my more real use case unfortunately where actually it is the host runtime that has to call callback. Any other way for the host to invoke call_indirect? I know emscripten exposes the function table as __indirect_function_table for example. Anything like that here?

[MaxGraey]

Well In this case, you can refactor you code to this:

function increment(input: i32): i32 {
  return input + 1;
}

export function callback(fn: i32, input: i32): i32 {
  return call_indirect(fn, input);
}

export function call(input: i32): i32 {
  return callback(increment.index, input);
}

add --importTable or --exportTable (it depends what you want to get or to set indexes manually from host) option to asc.

Example in playground

Or wait for fix this bindgen issue =)

[dsyer]

Amazing. Thanks!