I can trace a function call with specific arguments with a command like this:
dbg:tpl(foo, bar, dbg:fun2ms(fun([baz,_]) -> return_trace(),
exception_trace() end)).
However, it's a long to type, I'd like to have a wrapper around it.
The naive solution doesn't even compile:
-module(d).
-export([mfa/3]).
mfa(M, F, A) ->
dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
exception_trace() end)).
because there are no return_trace() and exception_trace() functions in
the module. Even if it'd compile, I couldn't call it like this:
d:mfa(foo, bar, [baz, _]).
because the _ variable is not bound. Is there a simple workaround or
shall I start to read up on parse_transforms?
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This might not be answering the exact question you are asking, but have you
tried using the built in trace patterns ?
They can save you a lot of typing. The build in trace patterns are
documented in the dbg man page (under the tpl/0 function).
For example, you can use
dbg:tpl(foo, bar, x)
as an alias for
dbg:tpl(foo, bar, x, [{'_', [], [{exception_trace}]}]).
Best regards
Philip
On Tue, Nov 6, 2012 at 2:33 PM, Attila Rajmund Nohl <attila.r.n...@gmail.com
> I can trace a function call with specific arguments with a command like
> this:
> dbg:tpl(foo, bar, dbg:fun2ms(fun([baz,_]) -> return_trace(),
> exception_trace() end)).
> However, it's a long to type, I'd like to have a wrapper around it.
> The naive solution doesn't even compile:
> -module(d).
> -export([mfa/3]).
> mfa(M, F, A) ->
> dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
> exception_trace() end)).
> because there are no return_trace() and exception_trace() functions in
> the module. Even if it'd compile, I couldn't call it like this:
> d:mfa(foo, bar, [baz, _]).
> because the _ variable is not bound. Is there a simple workaround or
> shall I start to read up on parse_transforms?
> _______________________________________________
> erlang-questions mailing list
> erlang-questi...@erlang.org
> http://erlang.org/mailman/listinfo/erlang-questions
> I can trace a function call with specific arguments with a command like
> this:
> dbg:tpl(foo, bar, dbg:fun2ms(fun([baz,_]) -> return_trace(),
> exception_trace() end)).
> However, it's a long to type, I'd like to have a wrapper around it.
> The naive solution doesn't even compile:
> -module(d).
> -export([mfa/3]).
> mfa(M, F, A) ->
> dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
> exception_trace() end)).
> because there are no return_trace() and exception_trace() functions in
> the module. Even if it'd compile, I couldn't call it like this:
> d:mfa(foo, bar, [baz, _]).
> because the _ variable is not bound. Is there a simple workaround or
> shall I start to read up on parse_transforms?
> _______________________________________________
> erlang-questions mailing list
> erlang-questi...@erlang.org
> http://erlang.org/mailman/listinfo/erlang-questions
> I can trace a function call with specific arguments with a command like this:
> dbg:tpl(foo, bar, dbg:fun2ms(fun([baz,_]) -> return_trace(),
> exception_trace() end)).
> However, it's a long to type, I'd like to have a wrapper around it.
> The naive solution doesn't even compile:
> -module(d).
> -export([mfa/3]).
> mfa(M, F, A) ->
> dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
> exception_trace() end)).
> because there are no return_trace() and exception_trace() functions in
> the module. Even if it'd compile, I couldn't call it like this:
> d:mfa(foo, bar, [baz, _]).
> because the _ variable is not bound. Is there a simple workaround or
> shall I start to read up on parse_transforms?
> _______________________________________________
> erlang-questions mailing list
> erlang-questi...@erlang.org
> http://erlang.org/mailman/listinfo/erlang-questions
> I can trace a function call with specific arguments with a command like this:
> dbg:tpl(foo, bar, dbg:fun2ms(fun([baz,_]) -> return_trace(),
> exception_trace() end)).
> However, it's a long to type, I'd like to have a wrapper around it.
> The naive solution doesn't even compile:
> -module(d).
> -export([mfa/3]).
> mfa(M, F, A) ->
> dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
> exception_trace() end)).
As described in the docs ( http://www.erlang.org/doc/man/dbg.html#fun2ms-1), you'll need to include ms_transform.hrl if calling dbg:fun2ms inside a module, so this:
---------------
-module(d).
-include_lib("stdlib/include/ms_transform.hrl").
-export([mfa/3]).
mfa(M, F, A) ->
dbg:tpl(M, F, dbg:fun2ms(fun(Args) when Args==A -> return_trace(),
exception_trace() end)).
----------------
compiles and works to a certain extent.
> because there are no return_trace() and exception_trace() functions in
> the module. Even if it'd compile, I couldn't call it like this:
> d:mfa(foo, bar, [baz, _]).
This is more tricky, you cannot send unbound variables to a function - it has little to do with dbg:fun2ms. Either you have to write your own parse_transform, which cannot be used from the shell, or you could use the match_spec syntax for the variables in the argument list and skip fun2ms altogether...
Look at this in the shell:
1> dbg:fun2ms(fun([baz,A,_]) -> return__trace(),exception_trace() end).
[{[baz,'_'],[],[{return_trace},{exception_trace}]}]
The argument list is translated so that anonymous variables become the atom '_' and named variables become '$n', where n is an integer > 0. You can write your function as:
mfa(M, F, A) ->
dbg:tpl(M, F, [{A,[],[{return_trace},{exception_trace}]}]).
and call it as:
d:mfa(foo,bar,[baz,'_']).
In that case you will not need the parse_transform.
BTW, you can remove return_trace, exception_trace includes return_trace.
> because the _ variable is not bound. Is there a simple workaround or
> shall I start to read up on parse_transforms?
> _______________________________________________
> erlang-questions mailing list
> erlang-questi...@erlang.org
> http://erlang.org/mailman/listinfo/erlang-questions
