Re: Passing scalar data around

[Sisyphus]

----- Original Message -----
From: "Ken Williams" <[EMAIL PROTECTED]>
To: "Sisyphus" <[EMAIL PROTECTED]>
Cc: "Miah Gregory" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Wednesday, January 29, 2003 5:01 PM
Subject: Re: Passing scalar data around


>
> On Tuesday, January 28, 2003, at 09:02  PM, Sisyphus wrote:
> > For dynamic memory allocation use New(), Newz(), or Newc() - and
> > Safefree()
> > instead of free().
> > Btw, there are many perfectly functional modules around with XS code
> > containing 'malloc' and 'free'. I'm not sure precisely under which
> > circumstances it becomes an issue.
>
> I think that the reason those modules usually work fine is that under
> most circumstances, New() and the like are just #define'd
> straightforwardly in terms of malloc() and the like.  But if someone
> builds with perl's malloc() instead of the system's, there may be
> problems.
>

Thanks Ken.
I think that means that the advice to use New() instead of malloc() applies
equally to both Inline and XS.
Or does it apply to one more than the other ?

Incidentally, I've never had any trouble with malloc(), though, having
learnt of New(), I've hardly ever used it.

I have struck trouble with calloc(), which I similarly no longer use.

Here's a little demo script that produces that problem. (I had been wanting
to re-create this to be sure that the problem with calloc() really does
exist for me.)

---------------------------------------------
use Inline C => <<'EOC';

void calloc_fun()
{
   long *buffer;

   buffer = (long *)calloc( 400, sizeof( long ) );
   if( buffer != NULL )
      printf( "Allocated 400 long integers\n" );
   else
      printf( "Can't allocate memory\n" );
   free( buffer );
}

void malloc_fun()
{
   long *buffer;

   buffer = malloc( 400 );
   if( buffer != NULL )
      printf( "Allocated 400 long integers\n" );
   else
      printf( "Can't allocate memory\n" );
   free( buffer );
}

EOC

for(1..1000) {malloc_fun()} # No problem
print "\n\n";
for(1..100) {calloc_fun()} # Crashes after 22 iterations.
---------------------------------------------------

The C code is taken from the MSDN website demos.
I tried rewriting the calloc() call as:
buffer = calloc( 400, sizeof( long ) );

It made no difference.
Anyway, no big deal ..... I just find it curious.

Cheers,
Rob