[Vm-dev] socketRecordSize is probably not 64-bit friendly

[Holger Hans Peter Freyther]

On Sun, Mar 22, 2015 at 01:58:05PM -0400, David T. Lewis wrote:

> On my machine, sizeof(SQSocket) is 16 for both 32 bits and 64 bits. I would
> have expected it to be 12 for the 32-bit case, but maybe the compiler is
> aligning it differently for some reason.

yes, it should be 12 :)



> In any case, "Smalltalk wordSize * 3" would not be right, because the
> actual data structure is this:
> 
> 	typedef struct
> 	{
> 	  int   sessionID;
> 	  int   socketType;  /* 0 = TCP, 1 = UDP */
> 	  void  *privateSocketPtr;
> 	}  SQSocket, *SocketPtr;


$ vi test.c
struct SQSocket {
	int sessionID;
	int socketType;
	void *privateSocketPtr;
};

extern void bla(struct SQSocket*);

int foo(void)
{
	struct SQSocket sock;
	bla(&sock);
}

$ cc -o test.o -ggdb3 -c test.c

$ pahole test.o 
struct SQSocket {
	int                        sessionID;            /*     0     4 */
	int                        socketType;           /*     4     4 */
	void *                     privateSocketPtr;     /*     8     4 */

	/* size: 12, cachelines: 1, members: 3 */
	/* last cacheline: 12 bytes */
};


Does it really say 16 for you on ia32?