From: Viet Le <vietlq85@gmail.com>
To: "caml-list@inria.fr" <caml-list@inria.fr>
Subject: Re: [Caml-list] Macro expansion for logging with call site (file & line)
Date: Tue, 25 Jul 2017 22:26:02 +0100 [thread overview]
Message-ID: <CAG_8+G4V+LdnQetuDirz1JSzCrXYnVts8skrfcYJR3vCW1e=4g@mail.gmail.com> (raw)
In-Reply-To: <CAG_8+G68ZcbdbbVgbfSVF9kTKJTG9FaM129a8=Q26Zf8NSvubA@mail.gmail.com>
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The main point is to avoid dragging __LOC__ to line 9, and use a
function/operator instead. It would look pretty ugly to have: report __LOC__
"bad bug".
Thanks.
On 25 July 2017 at 22:17, Viet Le <vietlq85@gmail.com> wrote:
> Hi,
>
> I would like to write a logger in OCaml. In C++ it's pretty
> straightforward with macro expansion that gives correct call site (file &
> line):
>
> $ cat -n cpp-logger.cpp
> 1 #include <iostream>
> 2
> 3 #define LOG_START do {\
> 4 std::cerr << __FILE__ << ":" << __LINE__ << ": "
> 5 #define LOG_END std::endl; } while (0)
> 6
> 7 int main()
> 8 {
> 9 LOG_START << "Got problem!" << LOG_END;
> 10 return 0;
> 11 }
>
> $ ./a.out
> cpp-logger.cpp:9: Got problem!
>
> In OCaml we have __LOC__ and __LOC_OF__:
>
> http://caml.inria.fr/pub/docs/manual-ocaml/libref/Pervasives.html
>
> However it's not trivial to get correct call site:
>
> $ cat -n yahoo.ml
> 1 print_string "yahoo\n";;
> 2
> 3 Printf.printf "__LOC__ = %s\n" __LOC__;;
> 4
> 5 let report s =
> 6 let loc, _ = __LOC_OF__ s in
> 7 Printf.printf "LOC of the expression (%s): %s\n" s loc ;;
> 8
> 9 report "bad bug" ;;
>
> $ ./a.outyahoo
> __LOC__ = File "yahoo.ml", line 3, characters 31-38
> LOC of the expression (bad bug): File "yahoo.ml", line 6, characters 28-29
>
> I expect line 9 but I get line 6 in OCaml. I would appreciate some help to
> get this working. Does it involve campl4/5 / ppx?
>
> Thanks.
>
> --
> Kind regards,
> Viet
>
--
Kind regards,
Viet
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prev parent reply other threads:[~2017-07-25 21:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-25 21:17 Viet Le
2017-07-25 21:26 ` Viet Le [this message]
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