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From: Kevin S. Van Horn (Kevin.VanHorn_at_[hidden])
Date: 2002-11-02 16:14:17

A few months ago there was some talk about checking preconditions. In
some places in the Boost libraries, exceptions are thrown, and in others,
assert() or its equivalent is used. I mentioned that you generally want
to core dump when you're debugging, but in many enterprise settings this
is not acceptable for production code, and it is preferable to throw an
exception (e.g., abort a single transaction). What you really want is to
allow the user to choose which behavior you get.

If it does not already exist somewhere in the Boost internals, and nobody
else is already working on it, I propose to contribute a small debug
library to Boost. The intent is that this library both be used internally
to Boost and also made available to Boost users. Here are the essentials:

1. There are macros BOOST_DBG_ASSERT(e) and BOOST_DBG_ASSERT_MSG(e, msg).
These check that e is true, and either cause an abort or an exception
throw if e is false. The second form allows one to give additional
explanatory information if e is false.

2. If BOOST_NDEBUG is defined, then both of the above two macros are

3. If BOOST_NDEBUG is not defined but BOOST_DEBUG_THROW is defined, then
the DB_ASSERT macros throw an exception containing the test expression,
file number, line number, and (optional) explanatory message.

Over time I expect that additional debug facilities would be added to this
library, in response to user input. For example, I think it would be useful
to have facilities that make it easy to define checked iterators such as exist
in STLport's debug mode. However, I think it best to start with the
smallest useful unit of functionality.

I also would like to get more familiar with the Boost internals, and as I
review the code for various libraries I expect to be submitting patches /
enhancements that make use of the new debug facilities.


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