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comp.lang.c FAQ list · Question 4.2

Q: 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);

A: The pointer you declared is p, not *p. When you're manipulating the pointer itself (for example when you're setting it to make it point somewhere), you just use the name of the pointer:

	p = malloc(10);
It's when you're manipulating the pointed-to memory that you use * as an indirection operator:
	*p = 'H';

(It's easy to make the mistake shown in the question, though, because if you had used the malloc call as an initializer in the declaration of a local variable, it would have looked like this:

	char *p = malloc(10);
When you break an initialized pointer declaration up into a declaration and a later assignment, you have to remember to remove the *.)

In summary, in an expression, p is the pointer and *p is what it points to (a char, in this example).

See also questions 1.21, 7.1, 7.3c, and 8.3.

References: CT&P Sec. 3.1 p. 28

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