Re: [Boost-users] Extracting "friendly" information from boost::exception

Subject: Re: [Boost-users] Extracting "friendly" information from boost::exception
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2012-07-22 17:27:37

On Sat, Jul 21, 2012 at 2:50 PM, Andreas M. Iwanowski <namezero_at_[hidden]>wrote:

>  Dear boost experts.****
>
> ** **
>
> We are using boost::exception in a project of ours, and are trying to
> extract some information from an exception****
>
> to display to the user.****
>
> ** **
>
> For example, diagnostic_information(e) returns this:****
>
> ** **
>
> d:\projects\<project>\ClassName.cpp(376): Throw in function void
> __thiscall ClassName::CInetExceptionHandler<struct
> ClassName::BadLoginException>(class CInternetException *) const****
>
> Dynamic exception type: class boost::exception_detail::clone_impl<struct
> ClassName::BadLoginException>****
>
> std::exception::what: Unknown exception****
>
> [struct tag_implementation_ClassName_SpecificInfo_errstr *] = Error: 12014
> Context: 0 Message: The password was not allowed****
>
> ** **
>
> [struct tag_interface_CDataInterface_errstr *] = ClassName reports: Bad
> FTP login****
>
> ** **
>
> ** **
>
> What I want is to extract "Error: 12014 Context: 0 Message: The password
> was not allowed" or "ClassName reports: Bad FTP login"****
>
> from that exception.****
>
> ** **
>
> However, these exceptions may be generated in DLLs that the main program
> know nothing about.****
>
> ** **
>
> To simplify, here is what I do and want ot be happening:****
>
> ** **
>
> 1. Main program calls method in DLL****
>
> 2. Main program knows this method can throw expections of type
> boost::exception****
>
> 3. Main program catches such exception****
>
> 4. Main program obtains string that is user-friendly from this exception**
> **
>

Use boost::get_error_info. See
www.boost.org/doc/libs/release/libs/exception/doc/get_error_info.html.

Ideally, error messages shouldn't be passed in exception objects. Instead,
pass the information that the catch site needs to format the message. So,
I'd suggest that the "4. Main program obtains a string that is
user-friendly" should probably be "4. Main program formats a user-friendly
message out of the error_info objects stored in the exception."

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode