OCaml piqi difficulties

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Kenneth Adam Miller

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Jun 9, 2015, 4:34:32 PM6/9/15
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I've been using piqi for quite a while and it's done wonders for me.

Lately though, I've had some issues with transforming some types provided by another library into a piqi representation.

Essentially, I'm at a crossroads where I'm running into a compile error, and I'm not sure how to fix it. Here's the root of my problem:

Error: This expression has type Stmt_piqi.stmt list list
       but an expression was expected of type
         Bapservice_piqi.Bapservice_piqi.lifted_region =
           Bapservice_piqi.Bapservice_piqi.stmt_list list
       Type Stmt_piqi.stmt list is not compatible with type
         Bapservice_piqi.Bapservice_piqi.stmt_list =
           Bapservice_piqi.Bapservice_piqi.stmt list 
       Type Stmt_piqi.stmt is not compatible with type
         Bapservice_piqi.Bapservice_piqi.stmt =
           [ `cpuexn of Bapservice_piqi.Bapservice_piqi.cpuexn
           | `if_stmt of Bapservice_piqi.Bapservice_piqi.if_stmt
           | `jmp of Bapservice_piqi.Bapservice_piqi.jmp
           | `move of Bapservice_piqi.Bapservice_piqi.move
           | `special of Bapservice_piqi.Bapservice_piqi.special
           | `while_stmt of Bapservice_piqi.Bapservice_piqi.while_stmt ]



lifted_region is defined in my piqi file as a stmt list list (a list of instructions). Here's the part that I don't know: in piqi do I import the module instead of including it in order to get the compiler to see that the types are equivalent? 

(because they are, this is very much like debugging a phantom type error. Stmt_piqi.stmt is the same as Bapservice_piqi.stmt).

My thinking with the above question is that if I import the module in piqi, then the piqi command will *not* generate a whole new ml, different entirely to the ml that was compiled and included in the library that I'm using, bap (it currently *is*). In that case, the types will be equivalent and everything will compile nicely.

But I attempted to import the module in my piqi file, and that results in some compile error that I don't know how to solve:

Unbound module Stmt_piqi. 

Naturally, in my makefile for generating ml of piqi encoder/decoder ocaml modules, I have an include that points to the folder that contains the bap stmt.piqi file. So the piqi ocaml command succeeds, but now I need to tell ocaml how to resolve the stmt_piqi module (compiled away in bap.serialization). I'm using oasis, and I already have bap.serialization in my depends, and the generated piqi ml file is auto detected and the correct bap.serialization is propagated through as a specified package on the command line.

How do I get the compiler to either see type equivalence of the Bapservice_piqi.stmt type or to know where to get the Stmt_piqi module?

Kenneth Adam Miller

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Jun 9, 2015, 6:48:21 PM6/9/15
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To be more clear, after I thought about it a bit more, I think what I need is definitely one of two things, either: 

1) to edit is the include path, either for ocamlbuild or oasis. The problem is, the implementation for a module is already in the library path... In this way, it will know where to find the appropriate ml, or cmi, cmo/x
2) tell piqi how to fully qualify the module into the other library. 
 -> http://piqi.org/doc/ocaml/#piqitoocamlmapping
Speak of the devil, I think that might be it!

*edit* 
OK, so I think I got it down... now it's just a piqi usage issue.I can edit the library interface that I'm using to expose that functionality. Now I need to know:

.import [ module stmt .name XYZ ]

once I expose the module name, and I should be able to force it to be fully qualified with the above. Problem is, I need to have the module name be Bap.Std.Bap_types.Bil_types.Bil_piqi; the periods are required. Problem: I can't put periods or '/' in the name of the module in order to get it to work. Variations on quotes didn't seem to make a difference either...

How to get piqi to accept a fully qualified name?

Anton Lavrik

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Jun 10, 2015, 4:57:01 AM6/10/15
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Hi Kenneth, please see my comment here: https://github.com/alavrik/piqi-ocaml/issues/7 I've added a small change that should help.

Anton

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