Issue with br labels in the JS build

[dcodeIO]

Somehow, a module in text format like

(module
  (type $t0 (func (param i32)))
  (type $t1 (func))
  (import "env" "log" (func $log (type $t0)))
  (func $main (type $t1)
    block $B0
      block $B1
        br $B1
        i32.const 3
        call $log
      end
      i32.const 2
      call $log
    end
    i32.const 1
    call $log)
  (start 1))

becomes

(module
  (type $t0 (func (param i32)))
  (type $t1 (func))
  (import "env" "log" (func $log (type $t0)))
  (func $main (type $t1)
    block $B0
      block $B1
        br 3228196 (; INVALID ;)
        i32.const 3
        call $log
      end
      i32.const 2
      call $log
    end
    i32.const 1
    call $log)
  (start 1))

after parsing with libwabt.js. Note the invalid pointer value instead of the label on the br. Any ideas?

See: wasmerio/vscode-wasm#14 (comment)

[binji]

When I copy this in to the wat2wasm demo it seems to produce the correct output.

I think I see the problem, though -- if I modify wat2wasm/demo.js and comment out the call to module.resolveNames I get the behavior you're seeing:

Error: validate failed:
test.wast:4:40: error: function type variable out of range (max 2)
  (import "env" "log" (func $log (type $t0)))
                                       ^^^
test.wast:5:21: error: function type variable out of range (max 2)
  (func $main (type $t1)
                    ^^^
test.wast:8:9: error: invalid depth: 3228196 (max 2)
        br $B1
        ^^
...

So it seems like you should be able to fix by calling resolveNames on the module.

[dcodeIO]

Thanks binji, makes sense. Linked your solution on the original issue :)

[binji]

Now that I think of it, this should be clearer in the API as well. In C++ there is an assertion that validate/toBinary aren't called unless the names are resolved, so the JS version should probably thow an exception in that case.