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Subject: Re: [boost] 5 Observations - My experience with the boost libraries
From: John Phillips (phillips_at_[hidden])
Date: 2010-03-24 00:25:37

Tom Brinkman wrote:
> What is the point of having the source code, when it take an experienced
> developer many weeks to understand what the library is doing underneath?
> What is the practical value of a library that can only be maintained
> by the original developer(s)?
> This issue has surprised many, but has comes up often.
> If it takes more than a day to examine a libraries source code and
> have some idea what its doing, its very dangerous to use. This issue
> will cause many to avoid complex templated macro-style boost libraries.
> Tom Brinkman


   I disagree with the underlying principle of this argument, and I want
to expand on why.

   For some reason, people believe that because Boost comes with source
code, they can only use it if they can both read the source and maintain
it. This strikes me as contrary to the whole idea of a library.

   To my understanding, the reason to use a library is that the
underlying problem either is too cumbersome to allow for a new solution
to be built in a reasonable time, or because the solution contains some
set of subtle pitfalls that will lead a new development to make errors
that will not be obvious to diagnose or fix. In such a case, you off
load the work and specialized understanding needed to someone else, and
use what they produce.

   When using a library of any sort, there should be a limit to the
blind trust applied. You should combine whatever tests are provided with
the library along with tests created in house to assess the suitability
of the library for the intended use. If the library passes all the tests
you come up with that address your needs, and it passes the tests that
the developers came up with to address their vision of t=what it should
do, then you are assured that it is at least as good as anything you
would develop in house. So, you use it.

   Only if it fails at providing some identified need do you need to
worry about how to modify it and maintain it. (Almost all software does
fail, sooner or later, but until it does there is nothing to fix.) If it
is failing before you even try to use it, you contact the developer and
try to work toward improvement.

   If it happens to be simple, you can try to modify it yourself, but
this is always a dangerous course of action. After you create in house
modifications that your program depends on, you have cut yourself off
from all of the future development of the library without a potentially
large later development and merge effort. So, it is almost always better
to work with the providers of the library to get your requested fixes to
be a part of the future releases instead of making them independently
and hoping they will be compatible with future releases from a provider
who knows nothing of your changes. In general, this is a case of relying
on knowing the internal implementation of the library, instead of
depending on the provided interface. Almost no software promises
anything about the details of the internal implementation from one
release to the next, and it is almost always foolish to assume you know
what it will be.

   That means, good development practice implies that you never plan to
provide maintenance for a third party library wholly in house. So, any
argument that starts from wanting to provide it in house is already
starting from bad practice. From that foundation, it has no persuasive

   The truth is, third party libraries are tools provided by someone
else. When I use tools provided by someone else, I have a responsibility
to test them to generate reasonable assurance that they fulfill my
needs, and to work with a source that I think will be responsible in
those cases where new flaws are exposed. This is no different from using
closed source third party tools such as some of the Intel numerical
libraries, or the MS compilers. I might be able to hack the binaries to
do what I want (I work for a company that provides tools for analyzing
binaries and for modifying them, so this is possible. It is just
unlikely to work right.), but I would be making a mistake to try. If I
don't think Intel or MS are responsible enough to work with me when
flaws are discovered, then I should find ways not to use their tools. If
I use their tools, then I am committed to working with them to remediate
flaws, and I do not expect to be able to fix them independently, nor do
I think it would be a good course of action to do so if I could.

   So, a valid argument would be to say you don't think the Boost
developers would be responsible about trying to address problems you
exposed. If you believe that to be true, then that is a major problem
with Boost that we really do need to address.


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