On 1/8/2025 10:24 AM, Corinna Vinschen wrote:
On Jan 7 21:27, Ken Brown wrote:
On 1/7/2025 3:18 PM, Corinna Vinschen wrote:
- mmap_record::prot flag, should be an array of protection bits per page
(POSIX page i e., 64K, not Windows page).
Question: Since it only takes 3 bits to store all possible protections, do
you think it's worth the trouble to pack the protections, so that each byte
stores the protection bits for 2 pages? Or should I just use an array of
unsigned char, with 1 byte for each page? Or did you have something else in
mind?
I hadn't thought deeply about this. I had a vague notion of a ULONG
array to match windows protection bits, but, as you note above, we
really only need 3 bits.
I don't think we have to define this as a bit field array, given this
isn't readily available in C and you would have to add bitfield
arithmetic by yourself. So, yeah, a char or maybe better uint8_t
might be the best matching type here.
Another question: Adding this array to mmap_record, we have two flexible
arrays in the class: one for page_map and one for the protection array.
My understanding is that a class or struct can have only one flexible
array member, and it has to be at the end. What's the best way to deal
with that? The only thing I can think of is to use a pointer instead of
an array for the protections, and then allocate memory for it separately
when an mmap_record is created. Or is there a better way?
Thanks.
Ken
