Continue to Ask Copy Control

rabbitdxj

Foo f = 100;
equal
Foo f(100);
Is that right?

killingme

Foo f = 100;
equal
Foo f(100);
Is that right?
----------
no,
Foo f = 100; equivalent to the third case of my reprinted article
Foo f(100);//The second case of my reprinted article

luyamin

tokillingme:

Oh, that might be a problem with g++.

But vc6 also has problems, Foo f = 100; This sentence may be directly interpreted as Foo f(100);, but according to the introduction in "C++ Primer", this should not be the case.

killingme

But vc6 also has problems, Foo f = 100; This sentence may be directly interpreted as Foo f(100);, but according to the introduction in "C++ Primer", this should not be the case.
----------------
It shouldn’t be like this, see the third case of my reprinted article for details
----
3. T a = v;
....
The reason why it emphasizes semantics is because the standard says that this call can be optimized...
--------------

zfy010317

The upstairs is a translator or written by myself, messy.

zfy010317

I don't think this rule is necessary.

T v = 0;
T v(0);

The only difference is the explicit keyword.

killingme

The upstairs is a translator or written by myself, messy.
-----------
I didn’t write it myself, I don’t have such a high level yet~-~
Reproduced others, where is the mess, that article puts the structure of the object
T a;
T a(v);
T a = v;
All kinds of situations have been mentioned, and it is a reference to the C++ standard. I feel that it is both complete and correct.

luyamin

Found the answer by myself:

"C++ Primer" said:

The copy form of initialization is primarily supported for compatibility with C usage. When it can do so, the compiler is permitted (but not obligated) to skip the copy constructor and create the object directly.
The initialization of the copy form (ie, initialize with the = sign, I note) is mainly for compatibility with C usage. When this usage is supported, the compiler is allowed (but not forced) to skip the copy constructor and create the object directly.

I think this passage has already answered my question.

Thank you all upstairs, especiallykillingme.