[Caml-list] Re: Exception Typetexp.Error(_, _) when using Toploop

[Hongbo Zhang <bobzhang1988@gmail.com>]

On 8/10/12 5:30 PM, Jean-Baptiste Jeannin wrote:
> Hi all,
>
Greetings,
> I am getting a strange dynamic type error Typetexp.Error(_, _) when
> trying to compile files using Toploop. It is strange to me because the
> error appears or not depending on which directory I compile from (while
> adapting all the paths, of course). I narrowed it down to two small
> files but am now stuck. My understanding (from comments in
> http://caml.inria.fr/svn/ocaml/branches/gadts/typing/typetexp.ml) is
> that it is a type error that is happening when trying to dynamically
> interpret (using Toploop) a dynamically generated piece of code, located
> in a string.
>
> Here is how to reproduce the error. In a directory, create a
> subdirectory subdir, and in this subdirectory create a file tree.ml
> containing the code:
>
> type tree = Leaf | Node of tree * tree;;
>
> in the main directory, create a file prog.ml containing the code:
>
> let s = "let t = Tree.Leaf;;" in
> let lexed = Lexing.from_string s in
> let parsed = (!Toploop.parse_toplevel_phrase) lexed in
> Toploop.execute_phrase true Format.err_formatter parsed;;
>
>
> If trying to compile them inside subdir, it works fine:
>
> $ cd subdir
> $ ocamlc -o prog.exe -I .. toplevellib.cma tree.ml ../prog.ml
> $ ./prog.exe
> val t : Tree.tree = Tree.Leaf
>
> However, if trying to compile them from the top directory (which is what
> I would like to do), it does not work and raises a Typetexp.Error(_, _)
> exception at runtime:
>
> $ cd ..
> $ ocamlc -o prog.exe -I subdir toplevellib.cma subdir/tree.ml prog.ml
> $ ./prog.exe
> Fatal error: exception Typetexp.Error(_, _)
>
Are you sure tree.cmo is linked in?
what's the output of
ocamlobjinfo prog.exe?
> If putting both files in the same directory and compiling them together
> it works too (but I would prefer not to do that):
>
> $ ocamlc -o prog.exe -I subdir toplevellib.cma tree.ml prog.ml
> $ ./prog.exe
> val t : Tree.tree = Tree.Leaf
>
>
> I think what happens is that the Tree.Leaf is not recognized because the
> module Tree is not in the directory from which we are compiling. Any
> idea how to fix this, while keeping the directory structure and
> compiling from the top directory, or any better understanding of what is
> happening?
>
> Thanks,
> Jean-Baptiste Jeannin
>
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> Please note: the commands above were executed with OCaml 3.12.0. If you
> are using 4.00.0 my understanding (although not tested) is that you
> should replace "toplevellib.cma" by "+compiler-libs ocamlcommon.cma
> ocamlbytecomp.cma ocamltoplevel.cma" everywhere
>