Re: How to clear the nested vector?

["Bo Persson" <bop at gmb dot dk>]

----- Original Message ----- 
From: "Mr. H. Xia" <h.xia@sheffield.ac.uk>
To: "libstdc++" <libstdc++@gcc.gnu.org>
Sent: Tuesday, April 19, 2005 4:50 PM
Subject: How to clear the nested vector?


> Hi, all
>
> I am having problems with clearing a nested vector.
>
> for example:
>
> // face class, a user defined class.
> class face{
> int *A;
> public:
> void setup(unsigned n){
>   if(!A) A = new int [n];
> }
>
> ~face() {delete[] A}
> };


Shouldn't this have a copy constructor as well?


> // define the nested vector.
> vector< vector<face> > x;
>
> // somewhere
> x.resize(100);
>
> // somewhere
> face f;
> f.setup(5);
> x[20].push_back(f);
>
> /*
>  .
>  .
>  .
>  .
> */
>
> x.clear();
>
>
> but later when I clear x, the memory is not decreasing...
>
> Can someone tell me what is wrong with my procedure? Many thanks!
>
> Note: on Win32 with either VC6.0 , a simple x.clear() is working, but 
> on Linux no way is working.

That is a known bug in VC6.0, which is fixed in later versions. 
x.clear() should destroy the members of the vector, but is should not 
release the memory.


Bo Persson


> -- Johnix