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* E.14 * clean-up * add final * Added words to dictionary * cleanup * fix typo * Update CppCoreGuidelines.md
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@ -15992,80 +15992,56 @@ Sometimes, [`finally()`](#Re-finally) can make such unsystematic cleanup a bit m
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##### Reason
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A user-defined type is unlikely to clash with other people's exceptions.
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A user-defined type can better transmit information about an error to a handler. Information
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can be encoded into the type itself and the type is unlikely to clash with other people's exceptions.
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##### Example
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void my_code()
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throw 7; // bad
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throw "something bad"; // bad
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throw std::exception{}; // bad - no info
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Deriving from `std::exception` gives the flexibility to catch the specific exception or handle generally through `std::exception`:
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class MyException : public std::runtime_error
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{
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public:
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MyException(const string& msg) : std::runtime_error{msg} {}
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// ...
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throw Moonphase_error{};
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// ...
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}
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};
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void your_code()
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{
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try {
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// ...
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my_code();
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// ...
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}
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catch(const Bufferpool_exhausted&) {
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// ...
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}
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}
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// ...
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##### Example, don't
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throw MyException{"something bad"}; // good
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void my_code() // Don't
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{
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// ...
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throw 7; // 7 means "moon in the 4th quarter"
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// ...
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}
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Exceptions do not need to be derived from `std::exception`:
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void your_code() // Don't
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{
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try {
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// ...
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my_code();
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// ...
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}
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catch(int i) { // i == 7 means "input buffer too small"
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// ...
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}
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}
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class MyCustomError final {}; // not derived from std::exception
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##### Note
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// ...
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The standard-library classes derived from `exception` should be used only as base classes or for exceptions that require only "generic" handling. Like built-in types, their use could clash with other people's use of them.
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throw MyCustomError{}; // good - handlers must catch this type (or ...)
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##### Example, don't
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Library types derived from `std::exception` can be used as generic exceptions if
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no useful information can be added at the point of detection:
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void my_code() // Don't
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{
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// ...
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throw runtime_error{"moon in the 4th quarter"};
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// ...
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}
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throw std::runtime_error("someting bad"); // good
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void your_code() // Don't
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{
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try {
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// ...
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my_code();
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// ...
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}
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catch(const runtime_error&) { // runtime_error means "input buffer too small"
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// ...
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}
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}
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// ...
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**See also**: [Discussion](#Sd-???)
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throw std::invalid_argument("i is not even"); // good
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`enum` classes are also allowed:
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enum class alert {RED, YELLOW, GREEN};
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throw alert::RED; // good
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##### Enforcement
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Catch `throw` and `catch` of a built-in type. Maybe warn about `throw` and `catch` using a standard-library `exception` type. Obviously, exceptions derived from the `std::exception` hierarchy are fine.
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Catch `throw` of built-in types and `std::exception`.
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### <a name="Re-exception-ref"></a>E.15: Throw by value, catch exceptions from a hierarchy by reference
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@ -343,6 +343,8 @@ Murray93
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mutex
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mutexes
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mx
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MyCustomError
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MyException
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myMap
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MyMap
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myset
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