4.1 What are pointers really good for, anyway?
4.2 I'm trying to declare a pointer and allocate some space for it, but it's not working. What's wrong with this code?
char *p; *p = malloc(10);
4.3 Does *p++ increment p, or what it points to?
4.4 I'm trying to use pointers to manipulate an array of ints. What's wrong with this code?
int array[5], i, *ip; for(i = 0; i < 5; i++) array[i] = i; ip = array; printf("%d\n", *(ip + 3 * sizeof(int)));I expected the last line to print 3, but it printed garbage.
4.5 I have a char * pointer that happens to point to some ints, and I want to step it over them. Why doesn't
((int *)p)++;work?
4.6 Why can't I perform arithmetic on a void * pointer?
4.7 I've got some code that's trying to unpack external structures, but it's crashing with a message about an ``unaligned access.'' What does this mean?
4.8 I have a function which accepts, and is supposed to initialize, a pointer:
void f(int *ip) { static int dummy = 5; ip = &dummy; }But when I call it like this:
int *ip; f(ip);the pointer in the caller remains unchanged.
4.9 Suppose I want to write a function that takes a generic pointer as an argument and I want to simulate passing it by reference. Can I give the formal parameter type void **, and do something like this?
void f(void **); double *dp; f((void **)&dp);
4.10 I have a function
extern int f(int *);which accepts a pointer to an int. How can I pass a constant by reference? A call like
f(&5);doesn't seem to work.
4.11 Does C even have ``pass by reference''?
4.12 I've seen different syntax used for calling functions via pointers. What's the story?
4.13 What's the total generic pointer type? My compiler complained when I tried to stuff function pointers into a void *.
4.14 How are integers converted to and from pointers? Can I temporarily stuff an integer into a pointer, or vice versa?
4.15 How do I convert an int to a char *? I tried a cast, but it's not working.
4.16 What's wrong with this declaration?
char* p1, p2;I get errors when I try to use p2.
4.17 What are ``near'' and ``far'' pointers?