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Declare a void pointer.
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Declare a void pointer.
7,299 Views | (14 votes, avg: 4.21)
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void *malloc(size_t number_of_bytes);
I think the answer is simply
void* p;
malloc is just the library function called to allocated some memory and of course a void pointer will be returned , but it is the declaration of a void pointer.
Ofcourse declaring a void pointer means void* var;
we will use malloc to assign memory to var before using it ie before assigning it a value of any type.
void near * n_ptr;
Better is to use void *p.
Even you can associate the * or & to the type instead of the variable like void* p; But this may lead to a confusion when you go for this kind of declaration void* p, q.
By looking at this you may think q is also a void pointer but it is not so it becomes a ordinary variable.
To raushan:
we can declare a pointer of type void,but we cant declare a variable of type void bcoz datatype void doesnt exist.
Void pointers
At first glance, a void pointer seems to be of limited, if any, use. However, when combined with the ability to cast such a pointer to another type, they turn out to be quite useful and flexible.
Consider the example of the previous section, where we constructed a function pointer to a function of type void and argument int. Such a function pointer in this form could not be used for a void function with a different type of argument (for example, float). This can be done, however, through the use of void pointers, as the following example illustrates.
#include
void use_int(void *);
void use_float(void *);
void greeting(void (*)(void *), void *);
int main(void) {
char ans;
int i_age = 22;
float f_age = 22.0;
void *p;
printf(”Use int (i) or float (f)? “);
scanf(”%c”, &ans);
if (ans == ‘i’) {
p = &i_age;
greeting(use_int, p);
}
else {
p = &f_age;
greeting(use_float, p);
}
return 0;
}
void greeting(void (*fp)(void *), void *q) {
fp(q);
}
void use_int(void *r) {
int a;
a = * (int *) r;
printf(”As an integer, you are %d years old.\n”, a);
}
void use_float(void *s) {
float *b;
b = (float *) s;
printf(”As a float, you are %f years old.\n”, *b);
}
Although this requires us to cast the void pointer into the appropriate type in the relevant subroutine (use_int or use_float), the flexibility here appears in the greeting routine, which can now handle in principle a function with any type of argument.
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