On 09/10/2012, at 14:32, Bob Tanner <basic at us.netrek.org> wrote:
> On 2012-10-08 23:24:42 +0000, James Cameron said:
> 48 bytes is wrong.  32 bytes is right.  Your compiler might be
> aligning the structure members for performance.  Give a suitable
> alignment directive to your compiler.  We use __attribute__((packed))
> in the server code.  Check the offset to each member using whatever
> language facilities are available.  In C we can use sizeof() and
> offsetof().
> So here's the debug using Jame's excellent advise.
> typedef struct _youServerPacket
> {
>     char    type;				 /* SP_YOU */
>     char    pnum;				 /* Guy needs to know this... */
>     char    hostile;
>     char    swar;
>     char    armies;
>     char    tractor;
>     char    pad2;
>     char    pad3;
>     unsigned flags;
>     long    damage;
>     long    shield;
>     long    fuel;
>     unsigned short etemp;
>     unsigned short wtemp;
>     unsigned short whydead;
>     unsigned short whodead;
> } __attribute__ ((packed)) youServerPacketStruct;

If you really want types of a known width and signedness you should use stdint.h, then you have..
typedef struct _youServerPacket
    int8_t     type;				 /* SP_YOU */
    int8_t     pnum;				 /* Guy needs to know this... */
    int8_t     hostile;
    int8_t     swar;
    int8_t     armies;
    int8_t     tractor;
    int8_t     pad2;
    int8_t     pad3;
    uint8_t    flags;
    int32_t    damage;
    int32_t    shield;
    int32_t    fuel;
    uint16_t   etemp;
    uint16_t   wtemp;
    uint16_t   whydead;
    uint8_t    whodead;
} __attribute__ ((packed)) youServerPacketStruct;

This will always give you the same answer no matter the size of int/long/etc..

Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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