Re: [Caml-list] filename and line number.

[Gabriel Scherer <gabriel.scherer@gmail.com>]

There is a "macro" syntax extension that is distributed with Camlp4,
and can do basic cpp-like stuff, including __FILE__ and a __LOCATION__
macros.

For example, the following content, named test.ml:

  let test =
    __LOCATION__

When processed through 'camlp4o pa_macro.cmo', will result in:

  let test = Loc.of_tuple ("test.ml", 2, 13, 17, 2, 13, 29, false)

(To compile:  ocamlc -pp 'camlp4o pa_macro.cmo' ...)

The "Loc.of_tuple" call is a reference to a function implemented in
Camlp4 Loc module; if you make you project depend (at runtime, not
camlp4-time) on Camlp4 loc-handling libraries, you'll get functions to
manipulate the location and its information. You can also define your
own Loc module in test.ml:

  module Loc = struct
    let of_tuple
      ((file_name, start_line, start_bol, start_off, stop_line,
stop_bol, stop_off, is_ghost) as loc) =
        loc
  end

  let test =
    __LOCATION__

The source code (and some documentation in the head comment) for the
"macro" camlp4 extension is in
camlp4/Camlp4Parsers/Camlp4MacroParser.ml in the ocaml source tree.

The meaning of the weird tuple arguments can be found in the Camlp4
documentation. I have a not exactly up-to-date (I guess ocaml 3.11)
version of the documentation on my website, see:
  http://bluestorm.info/camlp4//camlp4-doc/Sig.Loc.html

Finally, Martin Jambon also has its own "cppo" tools mimicking cpp,
which I suppose doesn't rely on camlp4, and has __FILE__ and __LINE__
macros which may be in a more directly exploitable format. I have
never tried it though. See:
  http://martin.jambon.free.fr/cppo.html

On Tue, Aug 2, 2011 at 2:20 PM, Anders Fugmann <anders@fugmann.net> wrote:
> Hi,
>
> Do there exist a way to get filename and linenumber of the calling function
> - Or at least the of the current filename and line number?
>
> I guess this would involve a syntax camlp4 syntax extension, but I'm not a
> camlp4 wizard and google did not come up with any suggestions.
>
> Regards
> Anders Fugmann
>
>
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