c++ - Does the standard make any guarantee that adding a constructor does not change the size? -

lets have class

struct foo {     uint32_t x;     uint32_t y; }; 

does c++ standard make mention whether sizeof(foo) should same sizeof(bar) if bar adds constructor ?

struct bar {     uint32_t x;     uint32_t y;     bar(uint32_t = 1,uint32_t b = 2) : x(a),y(b) {} }; 

the reason why asking foo send across network void* , cannot change size, if possible add constructor.

i found related: here , here, there answers focus on virtuals changing size , looking more definite "[...] implementations know of [...]".

ps: avoid misunderstanding... not asking how constsruct foo , send void* nor asking workaround make sure size not change, curious, whether standard says sizeof in specific case.

c++ 98 guarantees layout “plain old data” objects , don't permit constructors.

c++ 11 introduces “standard layout types”, still guarantee layout, permit constructors , methods added (and permits non-virtual bases added exceptions empty classes , duplicates).