[gpm] Check return codes everywhere

[Markus Elfring]

> Maybe adding errno to gpm_report() as an additional argument
> and strerror() it, if it's non-zero could do the job.

Would you like to introduce this little improvement for better error explanations?


> I must confess that I would like to have gpm cleaned up much more,
> before we add more dependencies on other projects.

I am curious which refactorings will be acceptable for the current source files
to complete the error handling.


> I personally see no advantage using try{} catch(),

(C++) exceptions provide a means to support more powerful error reporting.
Will all function implementations stick to a traditional C coding style forever?

Usual design choices are described in greater detail in the article "Exception
Handling Alternatives" by Detlef Vollmann.
http://accu.org/index.php/journals/546


> the ACC idea looks somehow nice, maybe something for the future.

Are there any chances to integrate a tool like "AspectC++" into the software
build process?
http://aspectc.org/

How do you think about to write filters for specific function interfaces?

Regards,
Markus