How is it that this can happen?

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Their is a Spreadsheet /*then a*/ CreateObject(){} //I am confused how this is legal.
What does it mean?

C++

Spreadsheet CreateObject() { return Spreadsheet(3, 2); };
int main(){ }

What I have tried:

Their is a Spreadsheet /*then a*/ CreateObject(){} //I am confused how this is legal.
What does it mean?

Spreadsheet CreateObject() { return Spreadsheet(3, 2); };
int main(){ }

Posted 13-Dec-18 14:53pm

Member 13010616

Updated 13-Dec-18 21:06pm

Mohibur Rashid

v2

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Mohibur Rashid 13-Dec-18 22:48pm

What exactly are you talking about?

2 solutions

Solution 2

That is perfectly legal (and idiomatic) C++ code, due to RVO[^] there is usually no performance loss.

Posted 13-Dec-18 21:06pm

CPallini

Comments

KarstenK 14-Dec-18 5:17am

Thanks for the info. But it has its traps: https://docs.microsoft.com/en-us/previous-versions/ms364057(v=vs.80)

CPallini 14-Dec-18 5:59am

You are welcome. Traps? You know, C++ has tons of them. As a matter of fact programming in C++ is like playing Minesweeper. :-D
By the way 'naked new' usage is also discouraged nowdays, in favour of smart pointers, see for instance:
https://docs.microsoft.com/en-us/cpp/cpp/smart-pointers-modern-cpp?view=vs-2017
It is worth nothing the article is, in turn, a bit dated:
auto song2 = make_unique<song>(L"Nothing on You", L"Bruno Mars");
would be suggested, today :-)

KarstenK 14-Dec-18 6:55am

Smart pointers is a good point.

My C++ skills are a bit "old school" now ... ;-)

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KarstenK · Accepted Answer · 2018-12-13T20:27:00

This a function implementation in the format Object function body like

C++

int func() { return 0; };

It is not a good idea for objects because the Spreadsheet object is allocated in the function body and the a copy on the stack.

Better is to work with object pointers:

C++

Spreadsheet* CreateObject() { return new Spreadsheet(3, 2); };

Which you wont write into a function. And you need to delete the Spreadsheet* somewhere.