Re: Article on possible improvements to C++

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Tue, 01 Dec 2009 16:32:55 +0100

Message-ID:

<hf3crf$al$1@news.eternal-september.org>

* io_x:

"Alf P. Steinbach" <alfps@start.no> ha scritto nel messaggio
news:heajk5$ugs$1@news.eternal-september.org...

* dragan:

Alf P. Steinbach wrote:

  #include <stdio.h>

  struct S
  {
      void* operator new( size_t const size, char const* const blah )
      {
          printf( "allocation function called, arg = \"%s\"\n", blah );
          return ::operator new( size );
      }

      S( int const whatever )
      {
          printf( "constructor called, arg = %d\n", whatever );
      }
  };

  int main()
  {
      S* const p = new( "Get it?" ) S( 42 );
  }

are you sure all your "const" are right?

You can add some if you want.

are you sure that the memory point from p is not a memory leak?

p does leak.

It's not an example of memory management.

Is there anhoter way to call
"void* operator new( size_t const size, char const* const blah )"
other than "new( "Get it?" ) S( 42 )"?

Yes.

even if i write

  int main()
  {
      S* const p = new( "Get it?" ) S( 42 );

delete p;

}

it calls, the "delete p" string, the [default] distructor of S?

Yes.

------------------------
#include <stdio.h>
#include <stdlib.h>
#define P printf
#define i8 signed char
#define V void

struct S{
public:
void* (operator new)(size_t size, char* blah)
    {printf( "allocation function called, arg = \"%s\"\n", blah );
     return (::operator new)(size);
    }
S(int whatever)
    {Sarr=0;
     printf( "constructor called, arg = %d\n", whatever );
     if(whatever<=0) return;
     Sarr= (i8*) malloc(whatever);
     P("S(int)");
    }
S(){
     printf( "void costructor\n");
     Sarr= (i8*) malloc(1024);
     P("S()");
    }
~S(){
      printf("distructor\n");
      free(Sarr);
     }
i8* Sarr;
};

int main(void)
{// S* p=new("Get it?") S( 42 );
// S* p=new("Get it?") S;
// S* p=new("Get it?") S();
   S* p=new("Get it?")S;
delete p;
P("\nEND\n");
return 0;
}

here the memory pointed from p [ came from (::operator new)(size)]
is really free?

Don't know if you have introduced any undefined behavior or the like, but if
not, then yes it's freed.

Cheers & hth.,

- Alf