[erlang-questions] Line numbers for logging/errors.

[Hynek Vychodil]

May be I missed some, but it works for me in R11B-5

-module(temp).
-export([test/0]).
-define(log(Message, Var), log_message(?MODULE, ?LINE, Message, ??Var,
Var)).



log_message(Module, Line, Message, VarName, Var) ->
     io:format("log: {~p, ~p} ~s ~s = ~p~n", [Module, Line, Message,
               VarName, Var]).

test() ->
    X = {a,b},
    ?log("Unexpected post", X). % here is line 20

%end

$ erl -smp
Erlang (BEAM) emulator version 5.5.5 [source] [smp:1] [async-threads:0]
[hipe] [kernel-poll:false]

Eshell V5.5.5  (abort with ^G)
1> c(temp).
{ok,temp}
2> temp:test().
log: {temp, 20} Unexpected post X = {a,b}
ok
3>


On Wed, Mar 12, 2008 at 4:08 PM, Richard Kelsall <r.kelsall@REDACTED>
wrote:

> Nohl Attila Rajmund wrote:
> > Yes, erlang has excellent trace facilities, it shows me that the 'rfmm'
> > function was called - unfortunately it doesn't show that which of the 10
> > rfmm functions was called.
>
> Breaking a small subject off the main thread. I haven't written much
> Erlang yet so maybe I'm just missing something, but I get the impression
> Erlang won't tell me the line number when something goes wrong. I feel
> it would be useful to know this and very in keeping with the Erlang
> approach of making bugs nice and visible. So my vote while we're all
> requesting changes to Erlang :) is for more line number visibility.
>
> On a related subject I've played around with the LINE macro to tag
> my own logging/error messages with line numbers and the best I could
> produce was something like this :
>
>   -define(log(Line, Message, Var), log_message(?MODULE, Line, Message,
>           ??Var, Var)).  % LINE macro always gives '1' if I put it here.
>
>   log_message(Module, Line, Message, VarName, Var) ->
>      io:format("log: {~p, ~p} ~s ~s = ~p~n", [Module, Line, Message,
>                VarName, Var]).
>
> and then in my code I can do things like
>
>     ?log(?LINE, "Unexpected post", Other),
>
> This works fine, but it would be nice to just write
>
>     ?log("Unexpected post", Other),
>
> and get the line number somehow. Can this be done?
>
>
> Richard.
>
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>



-- 
--Hynek (Pichi) Vychodil
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