Whatever. PPC lets you do it as well (with a performance penalty). The reality is that gcc is lame -- doubles are aligned to 8 byte boundaries on the stack, or in the static section. Why shouldn't they be in a struct as well? Any reasonable ABI should have this be.

Nevermind that (at least on 32-bit OSes), this would produce an unaligned double:

class foo { double a; virtual void blah() { }; };

well..gcc (!=lame imho) does have the compiler flags and also things like:

struct foo { int x[2] __attribute__ ((aligned (8))); };

i think that as much as structs look simpler and are in just for the c compat, they can end up more or less as an 'issue trap'. i generally try to avoid them and unions asm-asp.

the class 'treatment' on the other hand will most likely have no performance penalty what so ever.

ps: basically the above line solves the alignment of 'b' as:
struct test1 { double b __attribute__ ((aligned (8))); };

and now 'b' is considered independent of the compiler flags (-mno-align-double / -align-double)

ps2:
/sorry for multiple posts/

or...alternatively using pragma pack, which should be more portable but apparently not recommended with gcc:

//-----------
#include

#pragma pack(push, 8) //align = 8
#pragma pack(8)

struct test1 { double b; };
struct test2 { int a; test1 b; };
test2 foo;

#pragma pack(pop) //pop back
#pragma pack()

int main()
{
printf("%dn",(int)&foo.b.b - (int)&foo);
return 0;
}
//-----------

yeah, the __attribute__ use is the only solution that realistically works on OS X. Have to do some #ifdefs etc so that you can make stuff compile on other compilers too. the #pragma packs dont work on OS X. gcc != lame, but whoever decided that structs with doubles should be packed to 4 byte boundaries on these ABIs was not very thoughtful. "Avoiding structs" is not a good idea, IMO, because of course classes are structs, too.