[Haskell-cafe] :Trace has no history

[Pepe Iborra]

The debugger only instruments interpreted code, so evaluations
occurring inside library code do not show up in :trace. This is not a
terrible problem in practice, since usually seeing the evaluations
occurring in your code is what you need to debug the problem.

But since :trace is not showing you any evaluations at all, I wonder
if the problem might be that your code is not interpreted.
In order to ensure that it is, delete all the *.hi and *.o temporary
files lying around. You can also simply invoke ghci with the
-fbyte-code command line option.

If that fails, please complete the paste of your session below with
your invocation of ghci. There might be something else going on.

Thanks,
pepe

On Wednesday, September 1, 2010, Steve Severance <steve at medwizard.net> wrote:
> How do I tell? Does this mean that if the exception is occurring in a
> haskell library I can't get to it? I am trying to run down a
> Prelude.read: No Parse error and I need to see the value that it is
> failing to parse on.
>
> Thanks.
>
> Steve
>
> On Tue, Aug 31, 2010 at 11:05 AM, Pepe Iborra <pepeiborra at gmail.com> wrote:
>> Hi Steve
>>
>> The debugger only traces calls in interpreted code. Perhaps the call
>> to myMethod is being made from object code?
>>
>> Admittedly, the ghci debugger can take some effort to learn to use
>> properly. Make sure that you give a look to the ghc user guide if you
>> haven't done so yet.
>>
>>
>> Best,
>> pepe
>>
>> On Tuesday, August 31, 2010, Steve <sseveran at gmail.com> wrote:
>>> I am trying to debug a problem in GHCI. I invoke my method with trace
>>> but when it breaks on exception i can't get this history. Output is
>>> below. Thanks.
>>>
>>>
>>> relude Symbols> :set -fbreak-on-exception
>>> Prelude Symbols> :trace myMethod
>>> Loading package HUnit-1.2.2.1 ... linking ... done.
>>> Loading package syb-0.1.0.2 ... linking ... done.
>>> Loading package base-3.0.3.2 ... linking ... done.
>>> Loading package old-locale-1.0.0.2 ... linking ... done.
>>> Loading package time-1.1.4 ... linking ... done.
>>> Loading package random-1.0.0.2 ... linking ... done.
>>> Loading package QuickCheck-1.2.0.0 ... linking ... done.
>>> Loading package Decimal-0.1.0 ... linking ... done.
>>> Loading package array-0.3.0.0 ... linking ... done.
>>> Loading package Diff-0.1.2 ... linking ... done.
>>> Loading package bytestring-0.9.1.5 ... linking ... done.
>>> Loading package containers-0.3.0.0 ... linking ... done.
>>> Loading package mtl-1.1.0.2 ... linking ... done.
>>> Loading package old-time-1.0.0.3 ... linking ... done.
>>> Loading package convertible-1.0.9 ... linking ... done.
>>> Loading package utf8-string-0.3.4 ... linking ... done.
>>> Loading package HDBC-2.2.6 ... linking ... done.
>>> Loading package HDBC-mysql-0.6.3 ... linking ... done.
>>> Loading package parsec-2.1.0.1 ... linking ... done.
>>> Loading package network-2.2.1.7 ... linking ... done.
>>> Loading package HTTP-4000.0.9 ... linking ... done.
>>> Loading package binary-0.5.0.2 ... linking ... done.
>>> Loading package digest-0.0.0.8 ... linking ... done.
>>> Loading package filepath-1.1.0.3 ... linking ... done.
>>> Loading package unix-2.4.0.0 ... linking ... done.
>>> Loading package directory-1.0.1.0 ... linking ... done.
>>> Loading package pretty-1.0.1.1 ... linking ... done.
>>> Loading package zlib-0.5.2.0 ... linking ... done.
>>> Loading package zip-archive-0.1.1.6 ... linking ... done.
>>> Loading package Core-0.0.1 ... linking ... done.
>>> Beginning Update
>>> Stopped at <exception thrown>
>>> _exception ::
>>>  e = GHC.Exception.SomeException (GHC.Exception.D:Exception _
>>>
>>> (GHC.Show.D:Show ...) ....)
>>>                                  (GHC.IO.Exception.IOError Nothing
>>> GHC.IO.Exception.UserError ....)
>>> [<exception thrown>] Prelude Symbols> :history
>>> Empty history. Perhaps you forgot to use :trace?
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>>>
>>
>> --
>> -- José Iborra        http://www.dsic.upv.es/~jiborra
>> -- UPV Valencia       Telf. (+34) 96 387 00 00 (ext) 83529
>> -- Camino de Vera s/n. 46022 Valencia (Spain)
>>
>
>
>
> --
> ------------------------------------
> Steve Severance
> c. 240.472.9645
> e. steve at medwizard.net
> ------------------------------------
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>

-- 
-- José Iborra        http://www.dsic.upv.es/~jiborra
-- UPV Valencia       Telf. (+34) 96 387 00 00 (ext) 83529
-- Camino de Vera s/n. 46022 Valencia (Spain)