Behavior of camlp4o when used with -pp?

Behavior of camlp4o when used with -pp?

[David Rajchenbach-Teller]

    Dear list,
 I'm currently faced with a weird behaviour (bug?) of camlp4.

Assuming the existence of a file foo.ml, possibly empty.

camlp4o -no_comments foo.ml

understands option "-no_comments" correctly and pretty-prints the
contents of foo.ml, minus comments


However, when using camlp4o as a preprocessor,

ocamlc -i -pp "camlp4o -no_comments" foo.ml
-no_comments: unknown or misused option
Use option -help for usage
File "foo.ml", line 1, characters 0-1:
Error: Preprocessor error



Is this normal? Is there a workaround for this?

Thanks,
 David

-- 
David Teller-Rajchenbach
 Security of Distributed Systems
  http://www.univ-orleans.fr/lifo/Members/David.Teller
   « Ce matin Un crétin A tué un chercheur. » (air connu)
   Latest News of French Research: System being liquidated. Researchers angry.

Re: [Caml-list] Behavior of camlp4o when used with -pp?

[Jake Donham]

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On Tue, Feb 10, 2009 at 12:20 PM, David Rajchenbach-Teller <
David.Teller@ens-lyon.org> wrote:

> camlp4o -no_comments foo.ml
>
> understands option "-no_comments" correctly and pretty-prints the
> contents of foo.ml, minus comments
>
>
> However, when using camlp4o as a preprocessor,
>
> ocamlc -i -pp "camlp4o -no_comments" foo.ml
> -no_comments: unknown or misused option
> Use option -help for usage
> File "foo.ml", line 1, characters 0-1:
> Error: Preprocessor error
>

The default Camlp4 printer is the "auto" printer, which checks if its output
fd is a TTY; if so it uses the OCaml printer (which has -no_comments), if
not it uses the DumpOCamlAst printer (which does not). The point of this is
to pass the serialized AST through to the compiler without reparsing, for
speed and also to preserve the original locations in code that's been
transformed by a syntax extension.

Basically there is no reason to use -no_comments with -pp. But if you really
want to you can also give -printer o to camlp4o so you always get the OCaml
printer instead of autoselecting.

Jake

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Re: [Caml-list] Behavior of camlp4o when used with -pp?

[David Rajchenbach-Teller]

Well, in that case, it's an attempt to work around a camlp4 bug. And I'm
not attempting to use -no_comments itself, it's just the shortest
example I could find of the behavior.

Thanks,
 David

On Tue, 2009-02-10 at 13:10 -0800, Jake Donham wrote:
> Basically there is no reason to use -no_comments with -pp. But if you
> really want to you can also give -printer o to camlp4o so you always
> get the OCaml printer instead of autoselecting.
> 
> Jake
> 
-- 
David Teller-Rajchenbach
 Security of Distributed Systems
  http://www.univ-orleans.fr/lifo/Members/David.Teller
   « Ce matin Un crétin A tué un chercheur. » (air connu)
   Latest News of French Research: System being liquidated. Researchers angry.