How to avoid dangling pointers?


 
Thread Tools Search this Thread
Top Forums Programming How to avoid dangling pointers?
# 1  
Old 12-20-2013
How to avoid dangling pointers?

To get rid of dangling pointers, after freeing the pointer, can we assign NULL. Is this be an acceptable solution. Since
Code:
free(NULL)

won't do any operation.

Code:
main(){
 void *ptr = malloc(10);
 free(ptr); 
 ptr = NULL;
 free(ptr);
}

# 2  
Old 12-20-2013
The second call to free() has no effect, stop after the assignment of NULL to the pointer.
# 3  
Old 12-20-2013
To avoid free-ing dangling pointers: "Don't do that". If you're finding your programs in situations where it's even trying to free dangling pointers, that's a big problem you should solve instead of just mitigating. Fix the problem.

Basically, you want it to crash when you do that. You want it to crash right now, when the problem is still on the stack, not when it's too late to find out what crashed it. There are some really badly-coded heaps out there, i.e. Microsoft, which will happily swallow bad data and crash far later under untraceable circumstances.

Last edited by Corona688; 12-20-2013 at 12:52 PM..
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Programming

Pointers and array

Hello, I read from a book exercise for a challenge. How to print out each letter of char array a by two different pointers pa and ppa in the example? I have tried my code for letter "r" by testing without full understanding as only the first one worked. #include<stdio.h> int main() { char... (17 Replies)
Discussion started by: yifangt
17 Replies

2. Programming

Pointer to pointers

Hi guys, I'm trying to understand pointers in C and made a simple example and I've problems with It. Can someone help? #include <stdio.h> #include <stdlib.h> #include <assert.h> int f1(char **str_); int main(int argc, char **argv) { char *str = NULL; f1(&str); ... (3 Replies)
Discussion started by: pharaoh
3 Replies

3. Programming

Problem With Pointers

Hi guys. What is the difference between these: 1. int *a; 2. int (*a); (2 Replies)
Discussion started by: majid.merkava
2 Replies

4. Programming

Need help with the Pointers in C

I have a special character called . When it is declared as a character variable its showing it can be printed. But when it is declared as a character pointer variable its showing it cannot be printed. I am just wondering why its happening like this.. c1 = '@'; c2 = ''; char *fp; fp="XX"; if... (1 Reply)
Discussion started by: sivakumar.rj
1 Replies

5. UNIX for Advanced & Expert Users

shared pointers

I am new to shared pointer conceot in C++ and hence require some clarification: For example: class A { public: virtual ~A() { } int x; }; typedef boost::shared_ptr<A>... (1 Reply)
Discussion started by: uunniixx
1 Replies

6. Programming

restricted pointers

Hi all. I am trying to use restricted pointers to allow the gcc compiler optimize the code, but I have not been able to make it work so far. I am testing with this code: #include <stdlib.h> #include <stdio.h> #include <time.h> #include <sys/time.h> void vecmult(int n, int * restrict a, int... (0 Replies)
Discussion started by: carl.alv
0 Replies

7. Programming

pointers

Hi I mash with pointers in C. I solve this problem about 5 hours and I don't know how I should continue. void InsertFirst (tList *L, int val) { tElemPtr new; if((new = malloc(sizeof(tElemPtr))) == NULL) Error(); new->data = val; new->ptr = L->frst; L->frst = new;... (2 Replies)
Discussion started by: Milla
2 Replies

8. Programming

pointers

is this a valid c declaration int (*ptr(int *b)); plz explain... (4 Replies)
Discussion started by: areef4u
4 Replies

9. Shell Programming and Scripting

functiom pointers

Hi all i wonder about function pointers as i never used them in my C code . could any tell me why and where exactly function pointers come into picture . thanq (1 Reply)
Discussion started by: Raom
1 Replies

10. Programming

Pointers to Arrays

Below is the program i tried to execute...... main() { static int a = {0,1,2,3,4}; static int *p = {a, a+1, a+2, a+3, a+4}; printf (\n %u %u %d, p, *p, *(*p) ); } This works, but i wanted to know why both a and *p are declared as "static". If we dont declare a as static... (2 Replies)
Discussion started by: Jayathirtha
2 Replies
Login or Register to Ask a Question