llvm-project/clang-tools-extra/docs/clang-tidy/checks/misc-throw-by-value-catch-b...

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.. title:: clang-tidy - misc-throw-by-value-catch-by-reference
misc-throw-by-value-catch-by-reference
======================================
`cert-err09-cpp` redirects here as an alias for this check.
`cert-err61-cpp` redirects here as an alias for this check.
Finds violations of the rule "Throw by value, catch by reference" presented for
example in "C++ Coding Standards" by H. Sutter and A. Alexandrescu.
Exceptions:
* Throwing string literals will not be flagged despite being a pointer. They
are not susceptible to slicing and the usage of string literals is idomatic.
* Catching character pointers (``char``, ``wchar_t``, unicode character types)
will not be flagged to allow catching sting literals.
* Moved named values will not be flagged as not throwing an anonymous
temporary. In this case we can be sure that the user knows that the object
can't be accessed outside catch blocks handling the error.
* Throwing function parameters will not be flagged as not throwing an
anonymous temporary. This allows helper functions for throwing.
* Re-throwing caught exception variables will not be flragged as not throwing
an anonymous temporary. Although this can usually be done by just writing
``throw;`` it happens often enough in real code.
Options
-------
.. option:: CheckThrowTemporaries
Triggers detection of violations of the rule `Throw anonymous temporaries
<https://www.securecoding.cert.org/confluence/display/cplusplus/ERR09-CPP.+Throw+anonymous+temporaries>`_.
Default is `1`.
.. option:: WarnOnLargeObject
Also warns for any large, trivial object caught by value. Catching a large
object by value is not dangerous but affects the performance negatively. The
maximum size of an object allowed to be caught without warning can be set
using the `MaxSize` option.
Default is `0`.
.. option:: MaxSize
Determines the maximum size of an object allowed to be caught without
warning. Only applicable if `WarnOnLargeObject` is set to `1`. If option is
set by the user to `std::numeric_limits<uint64_t>::max()` then it reverts to
the default value.
Default is the size of `size_t`.