Checking an interface against an implementation

Checking an interface against an implementation

[Daniel Bünzli]

Hello,

Is there a compiler invocation that allows to check that a particular  
cmo or cmx implements a given cmi ?

I have some compilation units which are completely transparent to  
each other (i.e no .mli). However for the final client of these units  
I provide constrained interfaces specified in another directory.  For  
example,

mylib/a.ml
mylib/b.ml
mylib/api/a.mli
mylib/api/b.mli

Whenever I compile an .mli to a .cmi I would like to check that its  
corresponding .cmo implements it. The problem is that syntactically  
correct cmi always compile whithout problems. So if my .cmo doesn't  
implement my .cmi I only get an (uninformative) error when I try to  
actually link these units with the client.

Thanks for your answers,

Daniel

Re: [Caml-list] Checking an interface against an implementation

[Richard Jones]

On Mon, Dec 05, 2005 at 11:24:29AM +0100, Daniel Bünzli wrote:
> Is there a compiler invocation that allows to check that a particular  
> cmo or cmx implements a given cmi ?

I think the tool you're looking for is "objinfo" -- on Linux it's
usually installed as "ocamlobjinfo".  However this tool only works on
.cmi's or .cmo's, not .cmx's.

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
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Re: [Caml-list] Checking an interface against an implementation

[Daniel Bünzli]

Le 5 déc. 05 à 12:46, Richard Jones a écrit :

> I think the tool you're looking for is "objinfo" -- on Linux it's
> usually installed as "ocamlobjinfo".  However this tool only works on
> .cmi's or .cmo's, not .cmx's.

Thanks for the info (however note that this tool doesn't seem to be  
installed by default, at least if you compile from the source).

However I think what I want to do is impossible, apparently cmo  
record the cmi they were compiled with (in my case the one  
automatically generated) and refuse to link if the client was  
compiled with a different cmi. In other words a .cmo can have only  
one .cmi, is that true ?

One way to achieve what I want is to do the following

mylib/a.ml
mylib/b.ml
mylib/mylib.ml
mylib/mylib.mli

Such that mylib.ml is :

module A = A
module B = B

and mylib.mli defines the constrained interfaces :

module A = sig ... end
module B = sig ... end

But I have the following two questions. Suppose I pack the objects  
files into a cma and cmxa,

1) Is there any performance impact when the client uses functions  
from A or B via Mylib ? Does it introduce an indirection ?

2) Don't I lose the benefit of cm(x)a ? I have the impression that  
here, even if the client uses only functions from Mylib.A, b.cmo (or  
b.cmx) will also be linked in. Is that right ?

Daniel