void strong_swap(bool &all_good, T &a, T &b) - Boost.Outcome documentation

# `void strong_swap(bool &all_good, T &a, T &b)`

The standard `swap()` function provides the weak guarantee i.e. that no resources are lost. This ADL discovered function provides the strong guarantee instead: that if any of these operations throw an exception (i) move construct to temporary (ii) move assign `b` to `a` (iii) move assign temporary to `b`, an attempt is made to restore the exact pre-swapped state upon entry, and if that recovery too fails, then the boolean `all_good` will be false during stack unwind from the exception throw, to indicate that state has been lost.

This function is used within `basic_result::``swap(basic_result &)` if, and only if, either or both of `value_type` or `error_type` have a throwing move constructor or move assignment. It permits you to customise the implementation of the strong guarantee swap in Outcome with a more efficient implementation.

Overridable: By Argument Dependent Lookup (ADL).

Requires: That `T` is both move constructible and move assignable.

Namespace: `BOOST_OUTCOME_V2_NAMESPACE`

Header: `<boost/outcome/basic_result.hpp>`

Last revised: June 24, 2019 at 21:09:37 +0100