Re: = delete - what does this do?

From:

Alberto Ganesh Barbati <AlbertoBarbati@libero.it>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 23 Jul 2008 06:29:44 CST

Message-ID:

<YHBhk.31953$Ca.15595@twister2.libero.it>

amarzumkhawala@gmail.com ha scritto:

I was looking at the std thread class for c++:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2497.html#thread.threads

I was wondering what the "= delete" does when declaring a constructor?

--> thread(const thread&) = delete;

The "= delete" is a new syntax that will be introduced in C++0x to
declare that a certain function will *not* be provided. It can be used
to suppress the implicit generation of the copy constructor (as in this
case) or assignment operator, replacing the common hackish idiom of
declaring them private. This allows the compiler to provide a more
meaningful diagnostic.

The = deleted can be used on any function, including non-member
functions. For example:

   void f(double x) { /* ... */ }
   void f(int) = deleted;

   f(1.0); // ok
   f(1); // error: function is deleted

without the deleted function, f(1) would have been converted 1 to 1.0
and f(double) would be called.

HTH,

Ganesh

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