Re: packing fun

Don't sure about what your problem is on padding.

#pragma pack(push)
#pragma pack(4)
struct Alice
{
    int Integer1;
    char Char1;
    // HERE COMPILER WILL ADD PADDING BYTES TO 0
    char u8Padding1[3];  // == 0
};

struct Bob : Alice
{
    char Char2;
    // HERE COMPILER WILL ADD PADDING BYTES TO 0
    char u8Padding2[3];  // == 0
};
#pragma pack(pop)

So in memory, we will have 2 structure which are both aligned on 4 bytes :
Integer1    Char1    u8Padding1    Char2    u8Padding2
|     4             1              3           |     1               3
|
+-------------------------------+---------------------+
|                  Alice                       |              Bob
|

If you don't want to loose space in memory (is there any warrior of low
memory using in C++ coding ;p) push & pop the stack to fit to the minimum
size required or reduced size of variables like this :

struct Alice
{
    int         i24Integer1 : 24;           // Will have previous Integer1
which fit in 24 bits instead 32
    int         i8Integer1   : 8;            // Will have previous Char1
};
==> sizeof (Alice) = 4 instead 8 and we keep 4 bytes alignment.

Vincent


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