== Why is this an issue?

Some exception classes are designed to be used only as base classes to more specific exceptions, for instance, ``++std::exception++`` (the base class of all standard {cpp} exceptions), ``++std::logic_error++`` or ``++std::runtime_error++``.


Catching such generic exception types is usually a bad idea because it implies that the "catch" block is clever enough to handle any type of exception.

=== Noncompliant code example

[source,cpp,diff-id=1,diff-type=noncompliant]
----
try {
  /* code that may throw std::system_error */
} catch (const std::exception &ex) { // Noncompliant
  /*...*/
}
----

=== Compliant solution

[source,cpp,diff-id=1,diff-type=compliant]
----
try {
  /* code that may throw std::system_error */
} catch (const std::system_error &ex) {
  /*...*/
}
----

=== Exceptions

There are cases, though, where you want to catch all exceptions because no exceptions should be allowed to escape the function, and generic ``++catch++`` handlers are excluded from the rule:

* In the main function
* In a class destructor
* In a ``++noexcept++`` function
* In an ``++extern "C"++`` function

Additionally, if the ``++catch++`` handler is throwing an exception (either the same as before, with ``++throw;++`` or a new one that may make more sense to the callers of the function) or is never exiting (because it calls a ``++noreturn++`` function, for instance ``++exit++``), then the accurate type of the exception usually does not matter any longer: this case is excluded too.

== Resources

* CWE - https://cwe.mitre.org/data/definitions/396[CWE-396 - Declaration of Catch for Generic Exception]
* {cpp} Core Guidelines - https://github.com/isocpp/CppCoreGuidelines/blob/e49158a/CppCoreGuidelines.md#e14-use-purpose-designed-user-defined-types-as-exceptions-not-built-in-types[E.14: Use purpose-designed user-defined types as exceptions (not built-in types)]


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Catch a more specific exception instead of a generic one.


=== Highlighting

type of the variable in the catch clause


'''
== Comments And Links
(visible only on this page)

=== on 17 Aug 2016, 16:15:17 Ann Campbell wrote:
I made some tiny edits [~alban.auzeill]

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]
