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- HUGE amount of operations.
HUGE amount of operations.
This seemingly small program:
produced this gigantic output:
I realy dont know what could cause all that things to happen, as it seems it just copys and moves a bit, not a lot, but THAT...!
BTW: I realise it prints just 1, not the real value! why?
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produced this gigantic output:
move constructed from value default constructed copy assignment move constructed from value default constructed move assignment destructor called... default constructed default constructed move assignment destructor called... default constructed copy assignment copy assignment move constructed from value default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... default constructed copy assignment copy assignment copy assignment move constructed from value default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... default constructed copy assignment copy assignment move assignment default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... destructor called... move constructed from value destructor called... destructor called... destructor called... destructor called... move constructed from value destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy assignment copy assignment copy constructed from object move constructed from value destructor called... move constructed from value default constructed copy assignment move constructed from value default constructed move assignment destructor called... move constructed from value destructor called... destructor called... destructor called... destructor called... move constructed from value 1 destructor called... destructed destructor called... move constructed from value destructor called... destructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... move constructed from value destructor called... move constructed from value default constructed copy assignment move constructed from value default constructed move assignment destructor called... move constructed from value destructor called... destructor called... destructor called... destructor called... destructed default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... default constructed copy assignment copy assignment move assignment default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... destructor called... destructor called... move constructed from value destructor called... destructor called... destructor called... destructor called... move constructed from value destructor called... destructor called... destructor called... |
I realy dont know what could cause all that things to happen, as it seems it just copys and moves a bit, not a lot, but THAT...!
BTW: I realise it prints just 1, not the real value! why?
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I don't think you constructed it correctly.
This part seems wrong:
Shouldn't it be something like this?
You might have accidentally triggered implicit casts the way you did it.
Also, the constructor taking an rvalue reference to T should be moving x. You're just copying it and pointlessly erasing the old value.
foo<foo<foo<foo<int>>>> a(foo<foo<foo<int>>>(foo<int>(10)));This part seems wrong:
foo<foo<foo<int>>>(foo<int>(10))Shouldn't it be something like this?
foo<foo<foo<int>>>(foo<foo<int>>(foo<int>(10)))You might have accidentally triggered implicit casts the way you did it.
Also, the constructor taking an rvalue reference to T should be moving x. You're just copying it and pointlessly erasing the old value.
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Where to begin...
This tells the compiler
1: call T's default constructor to initialize a
2: call T's default constructor again to initialize a temporary
3: call T's operator= to trash the value you just stored in a, and move over the contents of the temprary
4. call T's destructor
5: output "default constructed".
Start with writing constructors correctly.
There is also an ambiguity error with "a!=T(0)" which clang++ points out.
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This tells the compiler
1: call T's default constructor to initialize a
2: call T's default constructor again to initialize a temporary
3: call T's operator= to trash the value you just stored in a, and move over the contents of the temprary
4. call T's destructor
5: output "default constructed".
Start with writing constructors correctly.
There is also an ambiguity error with "a!=T(0)" which clang++ points out.
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| Also, the constructor taking an rvalue reference to T should be moving x. You're just copying it and pointlessly erasing the old value |
here's an example from a tutorial how to make a move constructor:
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(I added the 1. and 2.)
1.: COPYING!
2.: ERASING THE OLD VALUE!
OK, as I added im my original post, it printed the wrong value. I menaged to fix it, but (of course) it added a lot more lines to the output!
The new foo class:
The new (RIGHT) output:
For some reason the int() operator was calling the bool() operator. Anyway I fixed it, and unfortunatly added more output. Again, why?
and, does anyone know how to make improvements?
BTW, does std::move also sat the value to the default? That would be awsome.
The new foo class:
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The new (RIGHT) output:
default constructed copy assignment move constructed from value default constructed move assignment destructor called... default constructed default constructed move assignment destructor called... default constructed copy assignment copy assignment move constructed from value default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... default constructed copy assignment copy assignment copy assignment move constructed from value default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... default constructed copy assignment copy assignment move assignment default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy assignment copy assignment copy constructed from object default constructed copy assignment copy constructed from object copy constructed from object 10 destructor called... destructed destructor called... default constructed destructor called... destructed default constructed move assignment destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... default constructed default constructed copy assignment copy constructed from object copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructed default constructed default constructed move assignment destructor called... default constructed default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... default constructed copy assignment copy assignment move assignment default constructed default constructed move assignment destructor called... default constructed copy assignment move assignment default constructed move assignment destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed default constructed move assignment destructor called... default constructed copy constructed from object destructor called... destructor called... default constructed destructor called... destructor called... destructor called... default constructed destructor called... destructor called... |
For some reason the int() operator was calling the bool() operator. Anyway I fixed it, and unfortunatly added more output. Again, why?
and, does anyone know how to make improvements?
BTW, does std::move also sat the value to the default? That would be awsome.
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foo<int> is a type.
foo<foo<int>> is a type. This type requires the type foo<int> to exist.
foo<foo<foo<int>>> is a type. This type requires foo<int> and foo<foo<int>> to exist.
ad nauseum.
So when you instantiate a type of foo<foo<int>> you're instantiating an object of type foo<int> and an object of type foo<foo<int>>. When you instantiate an object of type foo<foo<foo<int>>> you're instantiating an object of type foo<int>, an object of type foo<foo<int>> and an object of type foo<foo<foo<int>>>. ad, nauseum.
Avoid doing this as much as possible, and work on your understanding of move semantics.
Here's your code, corrected to avoid generating so many temporaries with a different driver:
You can see how injecting unneeded temporaries into this can make it look much worse.
Your move constructor 'example' was dealing with raw pointers and ownership. Your code does not.
foo<foo<int>> is a type. This type requires the type foo<int> to exist.
foo<foo<foo<int>>> is a type. This type requires foo<int> and foo<foo<int>> to exist.
ad nauseum.
So when you instantiate a type of foo<foo<int>> you're instantiating an object of type foo<int> and an object of type foo<foo<int>>. When you instantiate an object of type foo<foo<foo<int>>> you're instantiating an object of type foo<int>, an object of type foo<foo<int>> and an object of type foo<foo<foo<int>>>. ad, nauseum.
| and, does anyone know how to make improvements? |
Avoid doing this as much as possible, and work on your understanding of move semantics.
Here's your code, corrected to avoid generating so many temporaries with a different driver:
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foo<int> a(10): move constructed from value destructor called... foo<foo<int>> b(10): move constructed from value move-constructed from object move constructed from value destructor called... destructor called... destructor called... foo<foo<foo<int>>> c(foo<int>(10)): move constructed from value move-constructed from object move constructed from value move-constructed from object move-constructed from object move constructed from value destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... foo<foo<foo<foo<int>>>> d(foo<foo<int>>(10)): move constructed from value move-constructed from object move constructed from value move-constructed from object move-constructed from object move constructed from value move-constructed from object move-constructed from object move-constructed from object move constructed from value destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... destructor called... Press any key to continue . . . |
You can see how injecting unneeded temporaries into this can make it look much worse.
Your move constructor 'example' was dealing with raw pointers and ownership. Your code does not.
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| does std::move also sat the value to the default |
Just a small clarification, hopefully.
std::move does nothing at all. It does not compile into any code.It is only if you use std::move() as an argument in a function call (including operators), and that function has both lvalue-reference and rvalue-reference overloads,
std::move tells the compiler to call to the rvalue overload of the function.
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