Small changes in the internal APIs for Wasm

[OlivierNicole]

This PR consists in a number of changes in the APIs of compiler/lib/ that @vouillon needed while developing wasm_of_ocaml.

This is part of a series of PRs intending to reduce the diff between js_of_ocaml and wasm_of_ocaml (see ocaml-wasm/wasm_of_ocaml#47).

It is best reviewed commit by commit.

[hhugo]

@OlivierNicole, I wonder if we could move faster by not grouping unrelated commits too much.
In this PR, some commits are trivial and could be merged very quickly, while some other will need much more discussion.

[OlivierNicole]

Sure, I was worried of the opposite effect of bombarding the repo with too many PRs, hence the grouping. Let me know what you think should be separate PRs.

[hhugo]

Sure, I was worried of the opposite effect of bombarding the repo with too many PRs, hence the grouping. Let me know what you think should be separate PRs.

I think you should at least move out the sourcemap api commit and the build info in sexp one

[OlivierNicole]

Done. In fact I think I won’t do a PR for the Source_map changes for now, hopefully I can make progress on #1617 soon enough that it won’t be needed for long.

[hhugo]

The CI is not happy. @vouillon mentioned elsewhere that it could be due to a missing Generate.init () possibly in js_of_ocaml_dynlink.ml

[OlivierNicole]

I still get this error:

 --- a/_build/default/compiler/tests-toplevel/test_toplevel.reference
+++ b/_build/default/compiler/tests-toplevel/test_toplevel.referencebcjs
@@ -4,4 +4,7 @@ Line 4, characters 2-4:
 Error: Syntax error
 Line 5, characters 0-16:
 Error: Unbound module "Missing_module"
-val y : float = 0.333333333333333315
+Dynlink: looking for symbol caml_float_of_int
+Dynlink: looking for symbol caml_float_of_int
+Line 1:
+Error: The external function "caml_float_of_int" is not available

in spite of the Linker.reset () that I added in js_of_ocaml_compiler_dynlink.ml. I’m not sure why.

[hhugo]

I still get this error:

 --- a/_build/default/compiler/tests-toplevel/test_toplevel.reference
+++ b/_build/default/compiler/tests-toplevel/test_toplevel.referencebcjs
@@ -4,4 +4,7 @@ Line 4, characters 2-4:
 Error: Syntax error
 Line 5, characters 0-16:
 Error: Unbound module "Missing_module"
-val y : float = 0.333333333333333315
+Dynlink: looking for symbol caml_float_of_int
+Dynlink: looking for symbol caml_float_of_int
+Line 1:
+Error: The external function "caml_float_of_int" is not available

in spite of the Linker.reset () that I added in js_of_ocaml_compiler_dynlink.ml. I’m not sure why.

You need to initialize the thing in compiler/bin-js_of_ocaml/link.ml inside f.

I think I'd be more confortable moving the explicit initialization to its own PR so that we can discuss alternative and correctness without holding on the rest of this PR.

[OlivierNicole]

Done. I have opened #1662 for explicit initialization.

[OlivierNicole]

Thanks!