Use `noexcept` when exiting a function because of a `throw` is impossible or unacceptable

Reason

To make error handling systematic, robust, and efficient.

Example

double compute(double d) noexcept
{
    return log(sqrt(d <= 0 ? 1 : d));
}

Here, we know that compute will not throw because it is composed out of operations that don't throw. By declaring compute to be noexcept, we give the compiler and human readers information that can make it easier for them to understand and manipulate compute.

Note

Many standard-library functions are noexcept including all the standard-library functions "inherited" from the C Standard Library.

Example

vector<double> munge(const vector<double>& v) noexcept
{
    vector<double> v2(v.size());
    // ... do something ...
}

The noexcept here states that I am not willing or able to handle the situation where I cannot construct the local vector. That is, I consider memory exhaustion a serious design error (on par with hardware failures) so that I'm willing to crash the program if it happens.

Note

Do not use traditional exception-specifications.

See also

discussion.