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Subject: Re: [boost] [exception] ostringstream like
From: Fabien Castan (fcastan_at_[hidden])
Date: 2010-08-16 10:21:57

> No, I mean that if you do advanced string manipulation in the exception
> itself, you may screw up, adn cause a bad_alloc beign thrown and masking
> your own exception.

Create an error sentence with some values inside is not really an
advanced string manipulation.
You can have 2 kinds of errors: bug inside a custom operator<< or a
memory problem.
There is no particular reason to not have sufficient memory to create an
error sentence when throwing something like a logic_error.

> Just make your own, informative exception type deriving from logic_error.
The problem is not really the kind of exception, but an easy way to
create message with boost exception tag system.

The idea is to create a new base class for tags allowing to use an
ostringstream with tags, which is not possible.
typedef ::boost::error_info<struct tag_message,std::ostringstream> message;

This little class only remap operator+ call to operator<< on an internal
typedef ::boost::error_info<struct
tag_message,::boost::error_info_sstream> message;

I use it in my code, but I ask here if we can hope to see such things in
boost exception.
I would prefer to use a standard boost object rather than a custom class.

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