Re: Trip report: March 2010 ISO C++ standards meeting
Thomas Richter wrote:
Herb Sutter wrote:
We discussed two things related to exception specifications:
noexcept (N3050), and deprecating exception specifications
(N3051). There was some spirited discussion of what happens
when you violate a promise not to throw. In the end, we
decided that in such a circumstance terminate() gets called,
and it s unspecified whether any cleanup is done for local
variables between the throw point and the point of the violated
noexcept. It s believed that for efficient implementations of
exception handling a noexcept will not add any overhead and
will not restrict optimization opportunities.
Let me ask a question on this: As I see it, the major benefit of
noexcept is that it offers the compiler an optimization opportunity,
i.e. additional information to unwrap the stack is not needed. Doesn't
the requirement to call terminate() imply that additional code must be
created by the compiler to cover the cases where an exception is thrown
nevertheless, e.g. as in
try {
...
} catch(...) {
terminate();
}
Good point/catch. It didn't occur to me when I first read Herb's
message. This decision deviates from the original proposal N2983:
"...The only impact of such an exception-specification is this:
if a function decorated with noexcept(true) throws an exception,
the behavior is undefined..."
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/
n2983.html#solution>
Cheers,
SG
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