calloc is a library function, as opposed to a system call, so it calling memset is no different from the caller doing so. calloc will do the write in "copy on

calloc is a library function, as opposed to a system call, so it calling memset is no different from the caller doing so. calloc will do the write in "copy on write". Calling memset on every byte in a buffer should qualify as "touching it". This is why I said "in user space".