Using __attribute((packed))__ on picky architectures

["Darren Rook" <route66@xxxxxxxxx>]

Hello,

the usage of __attribute__((packed)) on a structure is well
documented, but I am curious about the ramifications of using this on
an architecture that requires 16bit or 32bit alignment.

For example:

	struct test
	{
    	    UINT8  field1;
    	    UINT16 field2;
    	    UINT8  field3;
	} __attribute__((__packed__));

   struct test t;

   void handle(UINT16 *val)
   {
      // some code that works with val
   }

   handle(&t.field2);

If this code is used on a 16bit architecture that does not implicitly
allow 8bit addressing, the handle() function may cause an address
exception because field2 may not be 16bit aligned because of the
packing.

Is there some method to tell the compiler that *val may not be word
aligned, so the compiler can generate code to work around the
alignment issue (instead of assuming the *val will be word aligned)?

Thanks,
Darren