Variable order and location within the section - optimization level dependent

[Janáček Jiří]

-----Original Message-----
From: Ian Lance Taylor [mailto:iant@google.com] 
Sent: Wednesday, October 16, 2013 4:30 PM
To: Janáček Jiří
Cc: gcc-help@gcc.gnu.org
Subject: Re: Variable order and location within the section - optimization level dependent

On Wed, Oct 16, 2013 at 7:06 AM, Janáček Jiří <jiri.janacek@skoda.cz> wrote:
>
> I do know this approach. I have created sections with the appropriate address ranges and located the variables into those sections by the below mentioned attribute.
> If no optimization is turned on, then the order (means also the address offset of the variable) is correct.
> If -O1 is turned on, the variables order within the section is exactly opposite.
> If -O1 is turned on and the flag -fno-toplevel-reorder is turned on as well, then the order is equal to the requested one. But I would like to apply such a behavior (no reorder) just for some variables in some modules. Other modules should be optimized by -O1 level.
> So I am curious which attributes can define this behavior.

Please don't top-post.  Thanks.

It sounds like you are saying that you want to have your global variables appear in a specific order in a specific section.

There is no attribute that will make that happen.  Sorry.  The obvious workaround would be to use a struct.

Ian

------------------

Hello Ian,

Right, the obvious solution is to apply a struct - originally I intended to avoid this way (there are some internal reasons for that).
IMHO the description of the "-fno-toplevel-reorder" flag (http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options) is a bit confusing - I mean especially this section: "For new code, it is better to use attributes.”

Thanks for your support,
JiriJ