[Mono-dev] New error handling framework for mono

[Robert Jordan]

Hi,

Zoltan Varga wrote:
> Hi,
> 
>   I still it would be easier to simply pass a int* or use an int return
> value, instead of a structure which needs to be initialized/cleaned up, and
> store any excess state in TLS. This is because
> most code can't do anything with an error other than cleaning up and passing
> it up to the
> caller.
> 
> So the code below could look like:

I like this.

> 
>   err = foo ();
>   if (err)

Or the same pattern with excess state in TLS:

if (foo ())
	MonoError *err = mono_get_last_error ();
	...

Using the return value to signal an error condition
also makes the code more macro-able, e.g.:

#define MONO_CHECK(x) do { if ((x))
	abort (mono_get_last_error_message ()); } while (0)

#define MONO_TRY(x) if ((x)) goto cleanup


	MONO_CHECK (foo ());

and

	MONO_TRY (foo ());
	...

	cleanup:

Robert


> 
> 
>                                  Zoltan
> 
> On Thu, Aug 13, 2009 at 11:26 PM, Rodrigo Kumpera <kumpera at gmail.com> wrote:
> 
>> Hey,
>>
>> The attached patch implements the basics for the new MonoError struct that
>> will be used for error handling in the runtime.
>> It has only the basics to support the current exceptions the runtime handle
>> for it's operation.
>>
>> The usage is pretty much like the one in Paolo's email on the subject:
>>
>> gboolean do_stuff () {
>> MonoError error;
>> mono_error_init (&error, 0);
>> runtime_function_that_might_fail (..., &error)
>> if (!mono_error_is_ok (&error))
>>   goto fail;
>> return TRUE;
>>
>> fail:
>> mono_error_cleaup (&error);
>> return FALSE; //or raise an exception using mono_raise_exception
>> (mono_error_prepare_exception (&error));
>> }
>>
>> The idea is to replace all error handling code with using this (loader
>> error, type exception_data and JIT's exception_type).
>>
>> Still open is how this would be integrated on 2.6 and if functions should
>> error out if passed an already set error object.
>> The last point enables more concise code like:
>>
>> MonoError error;
>> MonoType *type = ...;
>> mono_error_init (&error);
>> MonoClass *class = mono_class_from_mono_type (type, &error);
>> mono_class_init (class, &error);
>> MonoMethod *method = mono_class_get_method_from_name (class, "Invoke", 1,
>> &error);
>> if (!mono_error_ok (&error))
>>   return NULL;
>> return mono_runtime_invoke (method, NULL, params, NULL);
>>
>> I left behind some aditional features I would like to add to help
>> development, like logging, signaling a breakpoint and
>> asserting if setting a second error to the same MonoError.
>>
>> It would be a good time to hear the feeback on everyone about this,
>> specially embedders, since this will be the basis for
>> error handling of the new API comming in 2.8.
>>
>> Please comment,
>> Rodrigo
>>
>>
>> _______________________________________________
>> Mono-devel-list mailing list
>> Mono-devel-list at lists.ximian.com
>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>
>>
> 
> 
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