Referencing this question and answer Memory alignment : how to use alignof / alignas? "Alignment is a restriction on which memory positions a value's first byte can be stored." Is there a portable way in C++ to find out the highest granularity of alignment that is required for instructions not to fault (for example in ARM)? Is alignof(intmax_t)
sufficient since its the largest integer primitive type?
Further, how does something in malloc align data to a struct's boundaries? For example if I have a struct like so
alignas(16) struct SomethingElse { ... };
the SomethingElse
struct is required to be aligned to a boundary that is a multiple of 16 bytes. Now if I request memory for a struct from malloc like so
SomethingElse* ptr = malloc(sizeof(SomethingElse));
Then what happens when malloc returns a pointer that points to an address like 40
? Is that invalid since the pointer to SomethingElse
objects must be a multiple of 16?
You might be looking for std::max_align_t