• Thomas Kuehne (7/7) Aug 23 2004 The alignment size of the type "real" is smaller than it's size.
• Russ Lewis (7/14) Aug 23 2004 Thinking about 32bit machines for a moment...real requires 3 reads or

"Thomas Kuehne" <eisvogel users.sourceforge.net> writes:

The alignment size of the type "real" is smaller than it's size.

real.sizeof: 10
real.alignof: 2

Maybe I don't get the point of ".alignof".
Shouldn't it be at least ".sizeof"?

system: Linux / i686

Thomas

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

Thomas Kuehne wrote:
 The alignment size of the type "real" is smaller than it's size.
 
 real.sizeof: 10
 real.alignof: 2
 
 Maybe I don't get the point of ".alignof".
 Shouldn't it be at least ".sizeof"?

Thinking about 32bit machines for a moment...real requires 3 reads or 
writes, so long as it is aligned to a 2 byte boundary.  Aligning it to a 
4 byte boundary (or even more) doesn't gain you anything.  You just 
don't want to hit an odd address, since then you might require 4 accesses.

On the other hand, you might be bad performance if a real crosses a 
cache line boundary...perhaps that is an argument for real.alignof=16 ?