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C 11 Move Constructor Not Called, Default Constructor Preferred
Question:
In C 11, when instantiating an object via another object, why might the move constructor not be called when it should be?
Answer:
Upon instantiation, the compiler may occasionally apply a technique known as copy elision. Copy elision allows the direct construction of a temporary object into the target it would be copied or moved into, bypassing the copy or move constructor/destructor pair.
The standard allows copy elision in the following circumstances:
In the given example, when instantiating z with X("test"), copy elision occurs because it is considered a temporary object that has not been bound to a reference. Consequently, it is constructed directly into z, bypassing the move constructor and constructing z using the default constructor instead.
Explicitly calling move(X("test")) prevents copy elision and forces the use of the move constructor, as observed in the modified output.
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