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Top Forums Programming Segfaults on pointer deletion Post 302503281 by gaurav1086 on Thursday 10th of March 2011 06:09:36 AM
Old 03-10-2011
Bug

Quote:
Originally Posted by ctote
Hey Everyone,

I have a check similar to this:
Code:
if (ptr)
{
   delete ptr;
   ptr = null;
}

When I'm debugging in AIX (using dbx), if I attempt to print the value of 'ptr' it says "ptr is not defined" - however, it still enters that if block. So, I'm getting segfaults on the delete statement. Can anyone suggest why the if() block is entered?
Hi ctote,

if a ptr is NOT NULL, then it is true, (for ex. containing a junk values, aka bad pointer). if you did not define your ptr to NULL when you declare/free them, you should be careful about re-using them. Try to print the 'ptr' before entering the 'if block' and after you exiting the 'if block' and see if there is any difference.

Cheers,
Gaurav.
 

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ATOMIC_DEC(3)						   BSD Library Functions Manual 					     ATOMIC_DEC(3)

NAME
atomic_dec, atomic_dec_32, atomic_dec_uint, atomic_dec_ulong, atomic_dec_ptr, atomic_dec_64, atomic_dec_32_nv, atomic_dec_uint_nv, atomic_dec_ulong_nv, atomic_dec_ptr_nv, atomic_dec_64_nv -- atomic decrement operations SYNOPSIS
#include <sys/atomic.h> void atomic_dec_32(volatile uint32_t *ptr); void atomic_dec_uint(volatile unsigned int *ptr); void atomic_dec_ulong(volatile unsigned long *ptr); void atomic_dec_ptr(volatile void *ptr); void atomic_dec_64(volatile uint64_t *ptr); uint32_t atomic_dec_32_nv(volatile uint32_t *ptr); unsigned int atomic_dec_uint_nv(volatile unsigned int *ptr); unsigned long atomic_dec_ulong_nv(volatile unsigned long *ptr); void * atomic_dec_ptr_nv(volatile void *ptr); uint64_t atomic_dec_64_nv(volatile uint64_t *ptr); DESCRIPTION
The atomic_dec family of functions decrement (by one) the variable referenced by ptr in an atomic fashion. The *_nv() variants of these functions return the new value. The 64-bit variants of these functions are available only on platforms that can support atomic 64-bit memory access. Applications can check for the availability of 64-bit atomic memory operations by testing if the pre-processor macro __HAVE_ATOMIC64_OPS is defined. SEE ALSO
atomic_ops(3) HISTORY
The atomic_dec functions first appeared in NetBSD 5.0. BSD
April 11, 2007 BSD
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