forked from OSchip/llvm-project
73 lines
2.4 KiB
ReStructuredText
73 lines
2.4 KiB
ReStructuredText
.. index:: Replace-AutoPtr Transform
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=========================
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Replace-AutoPtr Transform
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=========================
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The Replace-AutoPtr Transform replaces the uses of the deprecated class
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``std::auto_ptr`` by ``std::unique_ptr`` (introduced in C++11). The transfer of
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ownership, done by the copy-constructor and the assignment operator, is changed
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to match ``std::unique_ptr`` usage by using explicit calls to ``std::move()``.
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The transform is enabled with the :option:`-replace-auto_ptr` option of
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:program:`cpp11-migrate`.
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Migration example:
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.. code-block:: c++
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-void take_ownership_fn(std::auto_ptr<int> int_ptr);
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+void take_ownership_fn(std::unique_ptr<int> int_ptr);
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void f(int x) {
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- std::auto_ptr<int> a(new int(x));
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- std::auto_ptr<int> b;
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+ std::unique_ptr<int> a(new int(x));
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+ std::unique_ptr<int> b;
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- b = a;
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- take_ownership_fn(b);
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+ b = std::move(a);
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+ take_ownership_fn(std::move(b));
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}
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Known Limitations
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=================
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* If headers modification is not activated or if a header is not allowed to be
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changed this transform will produce broken code (compilation error), where the
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the headers' code will stay unchanged while the code using them will be
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changed.
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* Client code that declares a reference to an ``std::auto_ptr`` coming from code
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that can't be migrated (such as a header coming from a 3\ :sup:`rd` party
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library) will produce a compilation error after migration. This is because the
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type of the reference will be changed to ``std::unique_ptr`` but the type
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returned by the library won't change, binding a reference to
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``std::unique_ptr`` from an ``std::auto_ptr``. This pattern doesn't make much
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sense and usually ``std::auto_ptr`` are stored by value (otherwise what is the
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point in using them instead of a reference or a pointer?).
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.. code-block:: c++
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// <3rd-party header...>
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std::auto_ptr<int> get_value();
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const std::auto_ptr<int> & get_ref();
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// <calling code (with migration)...>
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-std::auto_ptr<int> a(get_value());
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+std::unique_ptr<int> a(get_value()); // ok, unique_ptr constructed from auto_ptr
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-const std::auto_ptr<int> & p = get_ptr();
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+const std::unique_ptr<int> & p = get_ptr(); // won't compile
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* Non-instantiated templates aren't modified.
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.. code-block:: c++
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template <typename X>
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void f() {
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std::auto_ptr<X> p;
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}
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// only 'f<int>()' (or similar) will trigger the replacement
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