RE: sizeof different in x86 and arm.

[David Korn <dkorn at pixelpower dot com>]

>-----Original Message-----
>From: Cliff Tsai [mailto:clifftsai@minecard.com.tw]
>Sent: 24 May 2001 11:42


>    I have a simple struct as follow
>    
>    struct test_align
>     {
>     unsigned char Name[21];
>     unsigned char Version[8];
>     };
>
>    But on cygwin for x86,the sizeof(struct test_align) is 29;
>    
>    but on cygwin for arm,the sizeof(struct test_align) return 32
>    
>    WHY.

  I guess it's getting aligned.  x86 is happy to read any datatype from
any alignment address but I believe ARM likes things to be long word
aligned, so it puts three padding bytes after Name[] so that the first
byte of Version[] is aligned to a multiple of 4 bytes.

  I don't think it should really need to do this for chars, but I don't
know ARM very well so I can't explain the motivation.  However, the
simplest way to fix it will be by using either the 'packed' or 'aligned'
attributes - look them up in the gcc manual/info pages.

        DaveK
-- 
*** RIP: Douglas Adams. So long, and thanks for all the books. ***


**********************************************************************
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.

This footnote also confirms that this email message has been swept by
MIMEsweeper for the presence of computer viruses.

www.mimesweeper.com
**********************************************************************

------
Want more information?  See the CrossGCC FAQ, http://www.objsw.com/CrossGCC/
Want to unsubscribe? Send a note to crossgcc-unsubscribe@sourceware.cygnus.com