Question

I need to have a static void* array[1024]; in a library and i need to have it set to NULL for every entries.

My question is about the best way to set the entire array to NULL, is a memset (array, NULL, sizeof (void*) * 1024) the best solution?

Answer 1

static pointers are automatically initialized to NULL. See C99:TC3 6.7.8, §10:

If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static storage duration is not initialized explicitly, then:

• if it has pointer type, it is initialized to a null pointer;
• if it has arithmetic type, it is initialized to (positive or unsigned) zero;
• if it is an aggregate, every member is initialized (recursively) according to these rules;
• if it is a union, the first named member is initialized (recursively) according to these rules.

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Also, contrary to what others have written,

memset(array, 0, sizeof(array)); 

isn’t guaranteed to result in null pointers. On some systems, a pointer with all its bits set to 0 might actually be valid. For mainstream systems, that’s not the case, but with embedded systems, one never knows.

The safe way to set all entries to a null pointer is to either loop over the entries yourself and set them to NULL, or to use an uninitialized static array which you can memcpy() over the array you want to set to NULL.