How to check whether all bytes in a memory block are zero

Question

I have a block of memory with elements of fixed size, say 100 bytes, put into it one after another, all with the same fixed length, so memory looks like this

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Answer 1

You could perhaps actually use memcmp without having to allocate a zero-valued array, like this:

static int memvcmp(void *memory, unsigned char val, unsigned int size)
{
    unsigned char *mm = (unsigned char*)memory;
    return (*mm == val) && memcmp(mm, mm + 1, size - 1) == 0;
}

The standard for memcmp does not say anything about overlapping memory regions.