mikroC - C Compiler for Microchip PIC microcontrollers
mikroC
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You can also compare pointers to zero value – this tests if pointer actually points to anything. All pointers can be successfully tested for equality or inequality to NULL:
if (pa == NULL) { ... } if (pb != NULL) { ... }
Note: Comparing pointers pointing to different objects/arrays can be performed at programmer’s responsibility — precise overview of data’s physical storage is required.
Pointer Addition
You can use operators +, ++, and += to add an integral value to a pointer. The result of addition is defined only if pointer points to an element of an array and if the result is a pointer pointing into the same array (or one element beyond it).
If a pointer is declared to point to type, adding an integral value to the pointer advances the pointer by that number of objects of type. Informally, you can think of P+n as advancing the pointer P by (n*sizeof(type)) bytes, as long as the pointer remains within the legal range (first element to one beyond the last ele- ment). If type has size of 10 bytes, then adding 5 to a pointer to type advances the pointer 50 bytes in memory. In case of void type, size of the step is one byte.
For example:
int a[10]; // array a containing 10 elements of int int *pa = &a[0]; // pa is pointer to int, pointing to a[0]
*(pa + 3) = 6; // pa+3 is a pointer pointing to a[3], // so a[3] now equals 6
pa++; // pa now points to the next element of array, a[1]
There is no such element as “one past the last element”, of course, but a pointer is allowed to assume such a value. C “guarantees” that the result of addition is defined even when pointing to one element past array. If P points to the last array element, P+1 is legal, but P+2 is undefined.
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