Re: [Ocaml-lib-devel] compilation issues

[Peter J. <pe...@jo...>]

Pietro Abate wrote:
> Hi all,
> I want to distribute extlib with my project and to do so I added a
> Makefile to it. When compiling it on debian unstable (ocaml 3.07)
> everything it's ok. When I try to compile the same code, with the same
> makefile and ocaml 3.06 (debian woody) I get a complain about extString:
> 
> [...]
> ocamlc -c extString.mli
> ocamlc -c extString.ml
> The implementation extString.ml does not match the interface extString.cmi:
> Modules do not match:
>   sig
>     exception Invalid_string
>     external length : string -> int = "%string_length"
>     external get : string -> int -> char = "%string_safe_get"
>     external set : string -> int -> char -> unit = "%string_safe_set"
>     external create : int -> string = "create_string"
>     val make : int -> char -> string
>     val copy : string -> string
> 
> [...]
> 
>     val lowercase : string -> string
>     val capitalize : string -> string
>     val uncapitalize : string -> string
>     type t = string
>     val compare : t -> t -> int
>   end
> The field `compare' is required but not provided
> The field `t' is required but not provided
> make[1]: *** [extString.cmo] Error 2
> #> 
> 
> my naive solution was to add
> type t = string
> let compare = compare in the extString.ml file.
> 
> now it compiles with ocmal 3.06, but it complains with 3.07 because 
> there's a dup definition...

I know it sounds silly, but are you sure you're using version 3.06?  The
reason I ask is that this problem would make perfect sense in 3.04,
because the compare and t fields in the standard String library were not
present in that version.  Also, Debian isn't distributing 3.06 at the
moment - stable is 3.04, testing and unstable are 3.07.

At any rate, since you're using OCamlMakefile it's pretty easy to work
round this, if you're willing to use a non-standard ExtLib.  Add
conditional compilation directives from your preprocessor of choice
using some suitable conditional symbol around the definitions of t and
compare in extString.ml, and a (*pp foo *) directive at the top of that
file to invoke that preprocessor.  Then write a simple configure script
that tries to compile a test that depends on String.compare and sets
PPFLAGS to define that symbol if it fails.

HTH