rspec/rules/S1181/cfamily/rule.adoc

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

=== Noncompliant code example

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

=== Compliant solution

[source,cpp]
----
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

* https://cwe.mitre.org/data/definitions/396[MITRE, CWE-396] - Declaration of Catch for Generic Exception
* https://github.com/isocpp/CppCoreGuidelines/blob/036324/CppCoreGuidelines.md#Re-exception-types[{cpp} Core Guidelines E.14] - Use purpose-designed user-defined types as exceptions (not built-in types)


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