HugeClass& LoveHugeStuff::giveBigStuff() {
HugeClass hc;
hc.doStuffThatMakeMeHuge();
return hc
}
returning a local object reference alternative
Author
Say I have a two classes LoveHugeStuff and HugeClass
now.. (syntax might be screwed, it is only an example)
You can either create it on the heap and return a pointer (thus forcing the client to free it), or use a smart pointer.
Although i do not understand what your exactly trying to accomplish, but perhaps you could use the return optimization. (assuming C++, not sure if this will work in other languages)
This looks very similar to:
HugeClass hc();
return hc;
But the compiler will optimize the first mentioned method.
When it sees syntax such as: return HugeClass(); it will build the object directly in the location of the outside return value. This means that no tempory object has to be contructed in the function and as a consequence the object doesn''t have to be copied. Thus saving a copy-constructor call as well as a destructor call.
class HugeClass{public: HugeClass(){ // this constructor does something that will make it huge }};HugeClass giveBigStuff(){ return HugeClass();}This looks very similar to:
HugeClass hc();
return hc;
But the compiler will optimize the first mentioned method.
When it sees syntax such as: return HugeClass(); it will build the object directly in the location of the outside return value. This means that no tempory object has to be contructed in the function and as a consequence the object doesn''t have to be copied. Thus saving a copy-constructor call as well as a destructor call.
quote:Original post by Direct4DA good compiler will optimise the second method, too.
This looks very similar to:
HugeClass hc();
return hc;
But the compiler will optimize the first mentioned method.
I just realized that the second method does not work.
It treats:
HugeClass hc();
as an function prototype.
So i should have written:
HugeClass hc;
return hc;
btw: just tested if my compiler (Borland Builder 6) would do the optimize you mentioned...
It won''t. (compiled as release build with all optimization options on)
It treats:
HugeClass hc();
as an function prototype.
So i should have written:
HugeClass hc;
return hc;
btw: just tested if my compiler (Borland Builder 6) would do the optimize you mentioned...
It won''t. (compiled as release build with all optimization options on)
Quote:Original post by CoriianderIt shouldn't. That's waht its designed for.
Even auto_ptr destroys the object when the function goes out of scope.
show us the code you tried.
Alternative solution:
IOW, the caller is responsible for constructing HugeClass.
void LoveHugeStuff::giveBigStuff(HugeClass *hc) { // Store a private pointer to hc hc->doStuffThatMakeMeHuge();}IOW, the caller is responsible for constructing HugeClass.
void LoveHugeStuff::giveBigStuff(HugeClass *& hc) { hc = new HugeClass; hc->doStuffThatMakesMeHuge();}This topic is closed to new replies.
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