 |
| Register | Login | |||||
 |
Main
| Memberlist
| Active users
| ACS
| Commons
| Calendar
| Online users Ranks | FAQ | Color Chart | Photo album | IRC Chat |
|
| | ||
|
| Register | Login | |||||
|
Main
| Memberlist
| Active users
| ACS
| Commons
| Calendar
| Online users Ranks | FAQ | Color Chart | Photo album | IRC Chat |
|
| | ||
| 0 user currently in Programming. | 3 guests |
| Acmlm's Board - I2 Archive - Programming - NULL Pointers |
 |  |  |
| Add to favorites | "RSS" Feed | Next newer thread | Next older thread |
| User | Post | ||
beneficii Lakitu Level: 36 Posts: 375/567 EXP: 299656 For next: 8454 Since: 06-27-04 From: Cordova, TN, USA Since last post: 14 hours Last activity: 6 hours |
| ||
| I wonder, If you malloc a pointer or create any variable, will it ever get assigned the address of 0 (NULL)? In other words, will a pointer ever get a NULL address from the system? (edited by beneficii on 07-30-05 01:09 PM) |
|||
Dish Spiny Level: 38 Posts: 489/596 EXP: 355646 For next: 14801 Since: 03-15-04 From: Disch Since last post: 18 days Last activity: 18 days |
| ||
| On most systems -- no, you will never get a return of 0 (except on error). However, that's why you're supposed to use NULL and not 0 (since were a system to have 0 a valid address, you would only have to redefine NULL to make it something else). I never stuck to that though, and I treat NULL as 0 always. Even if 0 were a valid address... the lowest you could get would probably be like 8 or 16 or something -- since memory allocation functions allocate a bit more than you request and prefix it with information (like allocated size, and boundary checks) |
|||
|
beneficii Lakitu Level: 36 Posts: 376/567 EXP: 299656 For next: 8454 Since: 06-27-04 From: Cordova, TN, USA Since last post: 14 hours Last activity: 6 hours |
| ||
Originally posted by Disch Whoo, that just took a load off my back! Thanks Disch! My guess is that 0 is used by the system somehow (like for BIOS or something). |
|||
Ramsus Octoballoon Level: 19 Posts: 153/162 EXP: 34651 For next: 1126 Since: 01-24-05 From: United States Since last post: 39 days Last activity: 71 days |
| ||
| When used as a pointer value in C, the constant 0 is always considered NULL according to the language's standard, not the actual memory address 0. In fact, the system can use any value it wants to represent a NULL pointer and the constant 0 will always be equivalent to it in any pointer context (e.g. assignment to a pointer variable). If you're doing system-specific C code and store pointer addresses in something not a pointer, like an integer, you'll need to typecast 0 as (void *) in order to store an actual NULL value. |
|||
|
HyperLamer <||bass> and this was the soloution i thought of that was guarinteed to piss off the greatest amount of people Sesshomaru Tamaranian Level: 118 Posts: 6167/8210 EXP: 18171887 For next: 211027 Since: 03-15-04 From: Canada, w00t! LOL FAD Since last post: 2 hours Last activity: 2 hours |
| ||
| No OS I know of would assign memory that low. That area's generally reserved for the OS or BIOS. OSes usually reserve the lowest memory addresses for themselves. |
| Add to favorites | "RSS" Feed | Next newer thread | Next older thread |
| Acmlm's Board - I2 Archive - Programming - NULL Pointers |
| | |
