Tue 2002-11-19 15:49, Stas Degteff (2:5080/102) wrote to andrew clarke:

 ac>> I found the bug!

 ac>> So, I think Msged and my XMSGAPI code were being compiled using 
 ac>> differing structure alignments.  But I seem to recall there were 
 ac>> explicit #pragma pack statements in the original SMAPI code.

 > This is not need: XMSG used as message buffer and only elements of this 
 > structure read/write.

No, there's more to it than that!

XMSG is also used as a parameter to MsgWriteMsg().  If an application
program thinks sizeof(XMSG) == 248, and the precompiled SMAPI library
thinks sizeof(XMSG) == 238, you will have CORRUPT DATA (as I demonstrated).

Also, in msgapi.h there is:

#define XMSG_FROM_SIZE  36
#define XMSG_TO_SIZE    36
#define XMSG_SUBJ_SIZE  72

#define XMSG_SIZE (94 + XMSG_FROM_SIZE + XMSG_TO_SIZE + XMSG_SUBJ_SIZE)

So, the library basically requires that sizeof(XMSG) MUST BE 36 + 36 + 72 +
94 == 138.  But ever since the #pragmas were removed there's been nothing
in the source code to tell the C compiler not to pad the structure!

Regards
Andrew

-- mail{at}ozzmosis.com

--- Msged/NT 6.1.1