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Re: problem with sizeof struct alignment

Demmer, Thomas wrote:

Andrew Hill <dru at treshna dot com> wrote

I have this struct

typedef struct { double arrival; double departure; char status; int bookingid; int userid; } RoomStatus;

I'm using gcc with no compiler options or flags. Under linux with gcc, sizeof(RoomStatus) returns me 28 - as i would expect. If I use a borland C++ compiler it also returns a sizeof 28. But with cygwin + gcc it returns a sizeof 32. I'm a bit confused. Does cgwin + gcc align to nearest 8bytes for structs? Is there a compiler option to tell it to use 4 byte alignment? Is it just me whos having this problem?

I checked the sizeof for int, double and char and they all correct,
changing the char to an int or specifically saying its a 4bit int
doens't seem to make any difference.

gcc -mno-align-double is your friend to achieve ABI compatibility. This mis-feature
was introduced with gcc-3.whatever. Search the mailing
list for a remark from Brian Ford giving a heads up on this problem.

Thanks I'll try that. Found the orginal post by Brian.

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