[cfe-dev] Proposed C++ optimization with big speed gains with big objects

[Klaim - Joël Lamotte]

On Tue, Sep 25, 2012 at 6:26 PM, Ladislav Nevery <neuralll at gmail.com> wrote:

> int a=1;
> a=2;
>
> The moment I agreed to assign new value I agreed to old value being lost.
> This is normal and expected behavior.
>

For the value yes, but not for the destructor call.

If my understanding is correct, if I have this kind of code:


class TextFile
{
public:
   TextFile( std::string path )
{
  m_file.open( path );
 // add checks here
}
   ~TextFile()
   {
      m_file.close();
   }

   TextFile& operator=( const TextFile& other )
   {
       // clear our file's content
   m_file.clear();
   // copy the content of other's file
   m_file.write( other.m_file );
   }

private:

   FileHandler m_file;

};

Then the standard guarantee me that the destructor will be called only if
the instance goes out of scope, not on copy or move.
If I understand correctly what you propose, this code wouldn't do what I
assume it would. It would call the destructor and then change the semantic
of the type.

Joel Lamotte
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20120926/705f0932/attachment.html>