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31 lines
1.5 KiB
Text
31 lines
1.5 KiB
Text
A tt(unique_ptr) hi(unique_ptr: move constructor) may be initialized
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using an rvalue reference to a tt(unique_ptr) object for the same type:
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verb(
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unique_ptr<type> identifier(other unique_ptr object);
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)
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The move constructor is used, e.g., in the following example:
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verb(
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void mover(unique_ptr<string> &¶m)
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{
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unique_ptr<string> tmp(move(param));
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}
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)
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Analogously, the assignment operator can hi(unique_ptr: assignment) be
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used. A tt(unique_ptr) object may be assigned to a temporary tt(unique_ptr)
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object of the same type (again move-semantics is used). For example:
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verbinclude(-a examples/uniqueother.cc)
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The example illustrates that
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itemization(
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it() tt(hello1) is initialized by a pointer to a dynamically alloctated
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tt(string) (see the next section).
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it() The tt(unique_ptr hello2) grabs the pointer controlled by tt(hello1)
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using a move constructor. This effectively changes tt(hello1) into a
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0-pointer.
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it() Then tt(hello3) is defined as a default tt(unique_ptr<string>). But
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then it grabs its value using move-assignment from tt(hello2) (which, as a
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consequence, is changed into a 0-pointer as well)
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)
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If tt(hello1) or tt(hello2) had been inserted into tt(cout) a
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emi(segmentation fault) would have resulted. The reason for this should now be
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clear: it is caused by dereferencing 0-pointers. In the end, only tt(hello3)
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actually points to the originally allocated tt(string).
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