!js-string implementation of caml_string_concat fix

[rickyvetter]

If you write some code like (note this is not an ascii x!):

str ^ " ×"

And have compiled your code with --disable use-js-string, then the concat will not work correctly. I've changed to an implementation that seems correct, but likely has quite a few extra conversions. I'm not sure exactly what the original function was doing, but it felt complicated and so I was a bit nervous about fixing in a lower-level way.

I'd like to have tests in place but I'm not sure what the infrastructure looks like for testing with these flags?

[hhugo]

then the concat will not work correctly.

What does that mean ? What's the behavior you're seeing ?

I'd like to have tests in place but I'm not sure what the infrastructure looks like for testing with these flags?

There are some test in compiler/tests-compiler/test_string.ml. They call Util.compile_and_parse but you might want to use Util.compile_and_run.

[hhugo]

Your implementation should just be equivalent to the existing one. If you inline a few function call. You get;

  s1.t & 6 && caml_convert_string_to_bytes(s1);
  var a = s1.c;
  s2.t & 6 && caml_convert_string_to_bytes(s2);
  var b = s2.c;
  var x = a + b;
  return new MlBytes(0, x, x.lenght);

while we currently have

  s1.t & 6 && caml_convert_string_to_bytes(s1);
  s2.t & 6 && caml_convert_string_to_bytes(s2);
  return new MlBytes(s1.t, s1.c + s2.c, s1.l + s2.l);

Also I wasn't able to reproduce your issue.

[rickyvetter]

Sorry for the noise. You're right. There's a more complicated issue that isn't with this primitive.