Wireshark-dev: Re: [Wireshark-dev] [Wireshark-commits] rev 35975: /trunk/epan/dfilter/ /trunk/e
From: Gerald Combs <[email protected]>
Date: Thu, 17 Feb 2011 09:49:58 -0800
On 2/17/11 1:23 AM, Guy Harris wrote:

> To correct this warning, examine the pointer for null value as shown in the following code:
> 
> 	#include <malloc.h>
> 	void f( )
> 	{
> 	  char *p = ( char * )malloc ( 10 );
> 	  if ( p ) 
> 	  {
> 	    *p = '\0';
> 	    // code ...
>     
> 	    free( p );
> 	  }
> 	}
> "
> 
> (not "if ( p != NULL )", just "if ( p )").

That doesn't produce any errors with "/analyze". The following tests
compile without errors as well:

--------
#include <malloc.h>

void f( )
{
  char *p;

  if (p = ( char * ) malloc( 10 )) {
    *p = '\0';
   free( p );
  }
}
--------

--------
#include <malloc.h>
#include <stdlib.h>

void f( )
{
  char *p;
  int testval = 1;

  if (((p = ( char * ) malloc( 10 )) != NULL) && testval) {
    *p = '\0';
   free( p );
  }
}
--------

However this produces an error:

--------
#include <malloc.h>

void f( )
{
  char *p;
  int testval = 1;

  if ((p = ( char * ) malloc( 10 )) && testval) {
    *p = '\0';
   free( p );
  }
}
--------

test.c(9) : warning C6011: Dereferencing NULL pointer 'p': Lines: 5, 6, 8, 9



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