things that store it as word size for alignment purposes (most common afaik), things that pack multiple books into one byte (normally only things like bool sequences/structs), etc
you can call malloc(1) ofc, but calling malloc_usable_size(malloc(1)) is giving me 24, so it at least allocated 24 bytes for my 1, plus any tracking overhead
yeah, as I said, in a stack frame. not surprised a compiler packed them into single bytes in the same frame (but I wouldn’t be that surprised the other way either), but the system v abi guarantees at least 4 byte alignment of a stack frame on entering a fn, so if you stored a single bool it’ll get 3+ extra bytes added on the next fn call.
computers align things. you normally don’t have to think about it. Consider this a TIL moment.
things that store it as word size for alignment purposes (most common afaik), things that pack multiple books into one byte (normally only things like bool sequences/structs), etc
Nope. bools only need to be naturally aligned, so 1 byte.
If you do
struct SomeBools { bool a; bool b; bool c; bool d; };its 4 bytes.
sure, but if you have a single bool in a stack frame it’s probably going to be more than a byte. on the heap definitely more than a byte
Nope. - if you can’t read RISC-V assembly, look at these lines
sb a5,-17(s0) ... sb a5,-18(s0) ... sb a5,-19(s0) ...That is it storing the bools in single bytes. Also I only used RISC-V because I’m way more familiar with it than x86, but it will do the same thing.
Nope, you can happily
malloc(1)and store a bool in it, ormalloc(4)and store 4 bools in it. A bool is 1 byte. Consider this a TIL moment.c++ guarantees that calls to malloc are aligned https://en.cppreference.com/w/cpp/memory/c/malloc .
you can call
malloc(1)ofc, but callingmalloc_usable_size(malloc(1))is giving me 24, so it at least allocated 24 bytes for my 1, plus any tracking overheadyeah, as I said, in a stack frame. not surprised a compiler packed them into single bytes in the same frame (but I wouldn’t be that surprised the other way either), but the system v abi guarantees at least 4 byte alignment of a stack frame on entering a fn, so if you stored a single bool it’ll get 3+ extra bytes added on the next fn call.
computers align things. you normally don’t have to think about it. Consider this a TIL moment.