padding mechanism in structures

[Roman Mashak]

Hello, All!

Could you please explain me how is the padding of 'structure' fields is
made?

For example:

struct {
char a1;
int a2;
double a3;
} str;

When I'm checking "sizeof str" in GCC compiler I get the value of size as
16, it means some bytes are padded right?

Thanks!

PS. Or, point me to Inet link, if there is one.

With best regards, Roman Mashak. E-mail: mr*@tusur.ru

[Jack Klein]

On Wed, 15 Jun 2005 15:34:34 +0200, "Mehta Shailendrakumar "
<sh************ *******@de.bosc h.com> wrote in comp.lang.c:

Please don't top-post in technical groups. Material you add belongs
after quoted material you are replying to. I have reformatted your
post and added my answer after your question, where they belong.

"Lawrence Kirby" <lk****@netacti ve.co.uk> wrote in message
news:pa******** *************** *****@netactive .co.uk...

On Wed, 15 Jun 2005 14:11:40 +0200, Mehta Shailendrakumar wrote:

see if this helps with sample code attachment
pack
#pragma pack( [ n] )

Note that the C language doesn't define a preprocessor directive called
#pragma pack. You compiler may provide one as an extension but you can't
assume that it will exist on other compilers or if it does it will act in
the same way.

Hello Lawrence,

I have fwded gcc compiler specific info.
Can you suggest portable way to control padding?
Thanks.

There is no portable way to control padding. Controlling padding is
not a C language issue, and is not necessary in any event.

And on some architectures attempting to modify padding will result in
hardware traps for misalignment.

--
Jack Klein
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