== Why is this an issue?

Throwing an exception from a destructor may result in a call to `std::terminate`.

By default, compilers implicitly declare destructors as `noexcept`, so `std::terminate` is called when they exit with an exception.
Destructors may still propagate an exception if they are explicitly declared as `noexcept(false)`.
However, even a destructor declared as `noexcept(false)` calls `std::terminate` when it throws during stack unwinding.

The following example illustrates the severity of the underlying problem:

The destructor of a container needs to call the destructors for all managed objects.
Suppose a call to an object's destructor throws an exception.
In that case, there are only two _conceptual_ ways to proceed:

1. Abort the destruction.
   This results in a partially destroyed object and possibly many more objects whose destructors are never called.
2. Ignore the exception and proceed with destroying the remaining objects.
   However, this potentially results in more partially destroyed objects if further destructors throw an exception.

Because both options are undesired, destructors should never `throw` exceptions.

=== What is the potential impact?

In most cases, throwing exceptions in destructors makes the program unreliable:

 * If `std::terminate` is called, the program terminates in an implementation-defined, abrupt, and unclean manner.
 * The program's behavior is undefined if a standard library component (a container, an algorithm, ...) manages a user-defined object that throws an exception from its destructor.

include::{docdir}/how_to_fix_it.adoc[]

== Resources

=== Documentation

include::{docdir}/documentation.adoc[]

=== External coding guidelines

* {cpp} Core Guidelines - https://github.com/isocpp/CppCoreGuidelines/blob/e49158a/CppCoreGuidelines.md#c36-a-destructor-must-not-fail[C.36: A destructor must not fail]
* {cpp} Core Guidelines - https://github.com/isocpp/CppCoreGuidelines/blob/e49158a/CppCoreGuidelines.md#c37-make-destructors-noexcept[C.37: Make destructors `noexcept`]
* MISRA {cpp}:2008, 15-5-1 - A class destructor shall not exit with an exception.

=== Related rules

include::{docdir}/related_rules.adoc[]