I am currently working on a website project written in OCaml and compiled to javascript using js_of_ocaml. It works pretty well as long as I have only one source file using the command ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax -syntax camlp4o -linkpkg -o file.byte file.ml but I would like to include several modules in my project. How can I do that ?
The other modules are actually a lexer and a parser poduced by ocamllex and menhir. I have read a tutorial on how to use ocamllex and menhir with js_of_ocaml but it makes wrong assumptions on where js_of_ocaml is installed (I installed it with opam) and it uses ocamlbuild and I want to know how to do it by hand without using an automated tool such as ocamlbuild.
I found the solution by trying to understand the makefiles for the official examples.
Here is my Makefile :
OBJS=file1.cmo file2.cmo file3.cmo
NAME=projectname
OCAMLC=ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax -syntax camlp4o
$(NAME).byte: $(OBJS)
$(OCAMLC) -linkpkg -o $# $(OBJS)
$(NAME).js: $(NAME).byte
js_of_ocaml $<
%.cmo: %.ml
$(OCAMLC) -c $<
...
ocamlbuild keeps a log of the operations it performs. After an ocamlbuild call, look at _build/_log and you will see all the commands that it has invoked, with full arguments etc. That's probably the easiest way for you to figure how to do it by hand.
(Regarding +site-lib assumptions and OPAM, that's something you should report to the authors of the tutorial, they'll want to make sure that it also works for OPAM users.)
It's taken a bunch of experimentation, but I finally figured out how to have ocamlbuild pass the same flags to ocamlfind as ocsigen use in those makefiles. I'm also using js_of_ocaml installed with OPAM.
For my test case, I created a very small example with two files - main.ml and square.ml.
square.ml:
let square x = x * x
main.ml:
let () = (Js.Unsafe.coerce Dom_html.window)##square <- Js.wrap_callback Square.square
The command to build this successfully:
ocamlbuild -use-ocamlfind -pkgs js_of_ocaml,js_of_ocaml.syntax -syntax camlp4o main.byte
This produces identical JS output to my initial test case where the square function was in main.ml. The ocamlbuild log shows exactly what I expect (two calls to ocamldep, two to ocamlc -c, one to ocamlc -linkpkg).
Related
I have this in a file named main.ml:
let () = JsooTop.initialize ()
I tried compiling the file using:
ocamlfind ocamlc -package js_of_ocaml -linkpkg -o main.byte main.ml
But this error appears:
File "main.ml", line 1, characters 9-27:
Error: Unbound module JsooTop
It appears that JsooTop is not present on my machine, so I ran opam install js_of_ocaml-toplevel, and tried compiling the file again using:
ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml-toplevel -linkpkg -o main.byte main.ml
js_of_ocaml main.byte
But I get warnings:
Warnings from ocamlfind:
findlib: [WARNING] Interface topdirs.cmi occurs in several directories: /usr/lib/ocaml, /usr/lib/ocaml/compiler-libs
Warnings from the js_of_ocaml executable:
There are some missing primitives
Dummy implementations (raising 'Failure' exception) will be used if they are not available at runtime.
You can prevent the generation of dummy implementations with the commandline option '--disable genprim'
Missing primitives provided by +dynlink.js:
caml_add_debug_info
caml_dynlink_add_primitive
caml_dynlink_get_current_libs
caml_dynlink_lookup_symbol
caml_dynlink_open_lib
caml_remove_debug_info
Missing primitives provided by +toplevel.js:
caml_get_current_environment
caml_get_section_table
caml_invoke_traced_function
caml_realloc_global
caml_reify_bytecode
caml_static_alloc
caml_static_free
caml_static_release_bytecode
caml_terminfo_setup
My question is: what is the proper way to compile a file that uses the JsooTop module?
First, make sure that the required OPAM packages are present:
opam install js_of_ocaml js_of_ocaml-toplevel
To build a program that uses the JsooTop module, compile the file in this way:
ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml-toplevel -linkpkg -o main.byte main.ml
js_of_ocaml --toplevel --dynlink +dynlink.js +toplevel.js main.byte
Note the inclusion of --toplevel, --dynlink, +dynlink.js, and +toplevel.js. The commands above will produce a JavaScript file named main.js.
I'm trying to build this program using js_of_ocaml. According to this answer, I've got the following line in my makefile
OCAMLC = ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax -syntax camlp4o -linkpkg -g -dtypes
However, when I try to build, I get the following error:
ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax -syntax camlp4o -linkpkg -g -dtypes -c types.ml
> File "types.ml", line 472, characters 11-12:
> Parse error: [type_longident] expected after ")" (in [type_ident_and_parameters])
> File "types.ml", line 1:
The offending line of the file is this:
type ('t,'v) parser = ('t list -> 'v -> unit) -> 't list -> unit
I'm still pretty new to OCaml, so I'm not totally sure what's going on.
What does the -syntax camlp4o do? What kinds of things in the source might I need to change to be compatible with js_of_ocaml?
camlp4o provides the same syntax as the vanilla OCaml syntax, but with slight incompatibility: parser is a special keyword in camlp4o. This is why parser is rejected if you use camlp4o syntax.
You can workaround this problem by renaming parser, or using PPX syntax extension of js_of_ocaml instead of CamlP4. Please check https://ocsigen.org/js_of_ocaml/api/Ppx_js for details of this newer syntax helper for js_of_ocaml.
I have a package named sundialsml, in which I want to load a slightly different .cm(x)a file depending on whether a subpackage named no_sens is loaded. Promisingly enough, the findlib 1.6.2 reference manual describes a "package predicate" feature:
[...] there are package predicates for every package that is finally
selected. [They] have the form "pkg_" plus the name of the package
(fully qualified).
So I wrote up this META file, where archive branches on the package predicate for the subpackage:
version = "2.6.2"
description = "OCaml interface to Sundials"
requires = "bigarray"
archive(byte) = "sundials.cma"
archive(byte,pkg_sundialsml.no_sens) = "sundials_no_sens.cma"
archive(native) = "sundials.cmxa"
archive(native,pkg_sundialsml.no_sens) = "sundials_no_sens.cmxa"
package "no_sens" (
version = "2.6.2"
description = "Sundials/ML without sensitivity analysis (CVODE, IDA, KINSOL)"
requires = "sundialsml"
)
But findlib loads sundials.cma regardless of whether the subpackage no_sens is loaded, e.g.:
# #use "topfind";;
- : unit = ()
Findlib has been successfully loaded. Additional directives:
#require "package";; to load a package
#list;; to list the available packages
#camlp4o;; to load camlp4 (standard syntax)
#camlp4r;; to load camlp4 (revised syntax)
#predicates "p,q,...";; to set these predicates
Topfind.reset();; to force that packages will be reloaded
#thread;; to enable threads
- : unit = ()
# #require "sundialsml.no_sens";;
/home/jun/.opam/4.01.0/lib/ocaml/unix.cma: loaded
/home/jun/.opam/4.01.0/lib/ocaml/bigarray.cma: loaded
/home/jun/.opam/4.01.0/lib/sundialsml: added to search path
/home/jun/.opam/4.01.0/lib/sundialsml/sundials.cma: loaded
Same happens if I try branching on a top-level package, like ao. In fact, far as I can tell, predicates of the form pkg_foo are never defined (unless we say #predicates "pkg_foo";; of course).
Am I using package predicates incorrectly? Or are they not really implemented? If so, is there any other way to select different archives based on the presence/absence of subpackages?
Please note the point here is to compute the archive from the set of subpackages the user selected. So "why don't you use #predicates" is not the solution I'm looking for.
It looks like that the pkg_ predicates are not implemented for the #require directive at all. Of course, I may be wrong, since I inferred this by just greping the code and experimenting. In fact, it is only implemented in the frontend, so it is also not available if someone is using the library interface (so it will not work out of box for ocamlbuild). Also, the pkg_ predicate is set only for selected packages, not for installed one. Where selected means, that the package is in the set of dependencies.
Here is an example. We define package ttt with the following META:
archive(byte,pkg_ttt.foo) = "foo.cma"
archive(byte,pkg_ttt.bar) = "bar.cma"
package "foo" (
requires = "ttt"
)
package "bar" (
requires = "ttt"
)
Now we can verify, that it works:
$ ocamlfind c -only-show -linkpkg -package "ttt.bar" main.ml
ocamlc.opt -I opam/lib/ttt opam/lib/ttt/bar.cma main.ml
Note: I've used opam instead of a real path to my ocaml installation to shorten the output for readability.
$ ocamlfind c -only-show -linkpkg -package "ttt.foo" main.ml
ocamlc.opt -I opam/lib/ttt opam/lib/ttt/foo.cma main.ml
So, everything works, when we use the frontend. But if we will try from the toplevel:
# #require "ttt.foo";;
opam/lib/ttt: added to search path
Then nothing is loaded at all.
We can also try to use ocamlbuild:
$ ocamlbuild -classic-display -package ttt.foo main.byte
opam/bin/ocamldep.opt -modules main.ml > main.ml.depends
opam/bin/ocamlc.opt -c -I opam/lib/ttt -o main.cmo main.ml
opam/bin/ocamlc.opt -I opam/lib/ttt main.cmo -o main.byte
So nothing is linked, it doesn't work. But if you will use -use-ocamlfind option, it will work, since this option prescribes ocamlbuild to use ocamlfind fronted.
$ ocamlbuild -use-ocamlfind -classic-display -package ttt.foo main.byte
ocamlfind ocamldep -package ttt.foo -modules main.ml > main.ml.depends
ocamlfind ocamlc -c -package ttt.foo -o main.cmo main.ml
ocamlfind ocamlc -linkpkg -package ttt.foo main.cmo -o main.byte
So, to conclude, the idea was nice, and can work theoretically, but it is better not to use it, since the implementation is not complete.
I've written a simple MirageOS-based Unikernel to execute a basic HTTP GET call. While it is working without any problems when I run it as a Unix binary, the moment I configure it for XEN (mirage configure --xen) and launch the make command, I get the following error:
ocamlbuild -use-ocamlfind -pkgs lwt.syntax,cohttp.lwt,cohttp.lwt-core,mirage-console.xen,mirage-http,mirage-types.lwt -tags "syntax(camlp4o),annot,bin_annot,strict_sequence,principal" -tag-line "<static*.*>: -syntax(camlp4o)" -cflag -g -lflags -g,-linkpkg,-dontlink,unix main.native.o
+ ocamlfind ocamlopt -g -linkpkg -dontlink unix -output-obj -package mirage-types.lwt -package mirage-http -package mirage-console.xen -package cohttp.lwt-core -package cohttp.lwt -package lwt.syntax -syntax camlp4o unikernel.cmx main.cmx -o main.native.o
File "_none_", line 1:
Error: No implementations provided for the following modules:
Unix referenced from /home/mirage/.opam/system/lib/lwt/lwt-unix.cmxa(Lwt_engine),
/home/mirage/.opam/system/lib/lwt/lwt-unix.cmxa(Lwt_unix),
/home/mirage/.opam/system/lib/lwt/lwt-unix.cmxa(Lwt_io),
/home/mirage/.opam/system/lib/lwt/lwt-unix.cmxa(Lwt_log),
/home/mirage/.opam/system/lib/ipaddr/ipaddr_unix.cmxa(Ipaddr_unix),
/home/mirage/.opam/system/lib/xenstore_transport/xenstore_transport_lwt_unix.cmxa(Xs_transport_lwt_unix_client),
/home/mirage/.opam/system/lib/conduit/conduit-lwt-unix.cmxa(Conduit_lwt_unix),
/home/mirage/.opam/system/lib/cohttp/cohttp_lwt_unix.cmxa(Cohttp_lwt_unix_debug),
/home/mirage/.opam/system/lib/cohttp/cohttp_lwt_unix.cmxa(Cohttp_lwt_unix)
Command exited with code 2.
Compilation unsuccessful after building 7 targets (0 cached) in 00:00:03.
make: *** [main.native.o] Error 10
I just started working with MirageOS and OCaml so it might be a stupid question but right now I really don't know what to do.
You should not use Cohttp_lwt_unix. As the name suggests, it runs on unix, not on xen. If you want an example of a webserver that is xen-proof, you can look at this skeleton or at the code used by mirage-seal.
As #Drup says, you need to avoid any "unix" packages if you want to be portable. Instead, use a Mirage adaptor for cohttp. This one should work:
https://github.com/mirage/mirage-http
I have a three signatures A.mli,B.mli,and C.mli. Within them I have submodules Aa, Bb, and Cc respectively and also a signature for the implementations Ai, Bi, and Ci.
I have implemented them in a file called D.ml which looks like this
open A
open B
open C
module Ai : Aa = struct ... end
module Bi : Bb = struct ... end
module Ci : Cc = struct ... end
I compile them each in turn with the following commands:
ocamlfind ocamlc -linkpkg -thread -package core A.mli
ocamlfind ocamlc -linkpkg -thread -package core B.mli
ocamlfind ocamlc -linkpkg -thread -package core C.mli
ocamlfind ocamlc -linkpkg -thread -package core D.ml
which all succeed.
I then have a file E.ml where I try to use the modules Ai, Bi, Ci.
open A
open B
open C
module M = Ai(Ci)
(* do something else *)
However when I try to compile E.ml I get the
Error: Error while linking E.cmo:
Reference to undefined global `A`
I think I have to somehow include D.ml in the compilation step but I'm unsure how to.
Using ocamlc or ocamlopt compiler directly (even with the help of ocamlfind) is not an easy task, and should be left only for those, who write OCaml tools and very sure in what they're doing. So, in short, just use ocamlbuild, that is the default way of compiling things in OCaml world. Since, you're using Core library it would be also a good idea to use corebuild instead of ocamlbuild. corebuild is shipped with core, and is actually a small wrapper around ocamlbuild, that adds core dependencies, as well as some handy flags. So, with corebuild you can compile just with:
corebuild E.native
Without corebuild, you can compile with
ocamlbuild -pkg core E.native
ocamlbuild will do all the work for you, i.e., find all dependencies, sort them in correct order, invoke proper tools, etc... You just need this one, command.
If you're still interested in how to compile your example project properly, then you can ask ocamlbuild about this. Use -classic-display option, that will show you all intermediate commands,
ocamlbuild -use-ocamlfind -classic-display -pkg core E.byte
Will show you all steps. (You may need to ocamlbuild -clean, so that you can see all the steps from the start).