Re: [Lapackpp-devel] error handling

[Christian S. <sti...@tu...>]

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Dominik Wagenfuehr schrieb:
>> As for the output - I think this is usually redirected to
> ~/.xsession-errors,
> 
> What's the Windows pendant?

I don't know. I don't know windows that much.

>> and at the next failed assert() you will get a thrown LaException
>> instead of a failed assert. Is this what you wanted?
> 
> I will take a look at it. Maybe I should describe how I do my error
> handling in libraries. :)
> 
> I have a special static class called MyMessage with different enums for
> each error that can occur. If in a function an error occures I do
> 
> MyMessage::Set(ERROR_DEFINEMENT, "Class::FunctionA");
> return(true);
> 
> The functionB that called this failed functionA sees in the return
> argument that something went wrong. It now can decide if to goes one or do
> 
> MyMessage::Append("Class::FunctionB");
> return(true);
> 
> In this way I will create an error stack in the static class. At top
> level (that means in the GUI in most cases) I finally now can get the
> error and the stack
> 
> MyMessage::GetMessage() and MyMessage::GetStack()
> 
> and give the user a correct output. This means in a console application
> a console output, in a GUI-app maybe a little window message.

I think you can do this very well by using the new modifications in
laexcp.h, and then you enclose each lapackpp call by

try{
 // ...
}
catch (LaException &e) {
  MyMessage::Set(BLA, e.what() );
}

and continue accordingly.

> Further sometimes the user can decide what he wants to do now. In most
> cases he should copy the message, save all his data (as far as this is
> possible) and send a bug report to me. But if the GUI  just crashes
> (maybe after an hour of computing something) without any output the user
> may become a little impatient. ;)
> 
> I know that this is complicated especially implementing the return
> values of all functions (it took me a dew days to change my code.) And
> now I could not return something else but do most things by call by
> reference. The advantage of it is that my library (or better the program
> of a user with my library) never crashes unless the programmer does not
> catch my error output and just go on as nothing happens.
> 
> You can read something about this indirect error control in
> Piegl/Tiller: "The NURBS Book", p. 607, chapter "B-spline Programming
> Concept / Error control". There my be better programming books for it
> but this one explained it clear enough. :)

This kind of error handling seems a bit twisted to me, and at least the
"one static class" concept isn't any different than the standard libc
approach with one static variable errno. Whatever. I guess it will work
anyway.

Have fun,

Christian
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