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GSL::finally can make use of move semantics

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for eg consider this case
[code]
string value = "someVeryLongErrorMessageIAm";
finally([value] { PrintErrorMessage(value); }
[/code]
With the current changes before the call to PrintErrorMessage there will be 3 calls to copy constructor for string(1 when it's captured in closure, 2nd when finally is called and 3rd when it's passed to Final_act . With my patch there will be 1 call to the copy constructor and 2 to the move constructor for the scenario in example, so 2 potential deep copies will be saved for some objects.
Validated that code builds from root, and all tests pass after my change. Also validated that indeed copy constructor calls are saved for objects that support move semantics.
This commit is contained in:
saurabh singh 2015-09-27 16:11:12 +05:30
parent b40d3466c6
commit 437791e504
1 changed files with 5 additions and 2 deletions
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7
include/gsl.h
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@ -50,7 +50,7 @@ template <class F>
class Final_act
{
public:
explicit Final_act(F f) : f_(f) {}
explicit Final_act(F f) : f_(std::move(f)) {}
Final_act(const Final_act&& other) : f_(other.f_) {}
Final_act(const Final_act&) = delete;
@ -64,7 +64,10 @@ private:
// finally() - convenience function to generate a Final_act
template <class F>
Final_act<F> finally(F f) { return Final_act<F>(f); }
Final_act<F> finally(const F &f) { return Final_act<F>(f); }
template <class F>
Final_act<F> finally(F &&f) { return Final_act<F>(std::forward<F>(f)); }
// narrow_cast(): a searchable way to do narrowing casts of values
template<class T, class U>