First, a little of the history of this topic is
in order. In 1994, Tom Cargill published the seminal article
"Exception Handling: A False Sense of Security" (Cargill94).
It demonstrated conclusively that, at that time, the C++ community
did not yet fully understand how to write exception-safe code. In
fact, we didn't even know what all the important exception-safety
issues were, or how to correctly reason about exception safety.
Cargill challenged anyone to demonstrate a conclusive solution to
this problem. Three years passed. A few people wrote partial
responses to aspects of Cargill's example, but no one showed a
comprehensive solution.
Then, in 1997, Guru of
the Week #8 appeared on the Internet newsgroup comp.lang.c++.moderated. Number 8 generated
weeks of discussion and presented the first complete solution to
Cargill's challenge. Later that year, a greatly expanded version
that was updated to match the latest changes to draft standard C++
and demonstrating no fewer than three complete solutions, was
published in the September and November/December issues of
C++ Report under the title
"Exception-Safe Generic Containers." (Copies of those original
articles will also appear in the forthcoming book C++ Gems II [Martin00].)
In early 1999, on the Effective C++ CD (Meyers99), Scott Meyers included
a recombined version of the articles, together with Cargill's
original challenge, with the updated text of his classic books
Effective C++ and More Effective C++.
This miniseries has come a long way since its
original publication as Guru of the Week
#8. I hope you enjoy it and find it useful. Particular
thanks go to fellow committee members Dave Abrahams and Greg Colvin
for their insights into how to reason about exception-safety and
their thoughtful critiques of several drafts of this material. Dave
and Greg are, with Matt Austern, the authors of the two complete
committee proposals for adding the current exception-safety
guarantees into the standard library.
This miniseries tackles both major features,
exception handling and templates, at once, by examining how to
write exception-safe (works properly in the presence of exceptions)
and exception-neutral (propagates all exceptions to the caller)
generic containers. That's easy enough to say, but it's no mean
feat.
So come on in, join the fun, and try your hand
at implementing a simple container (a Stack that users can
push and pop) and see the issues involved with making it
exception-safe and exception-neutral.
