Re: why do we poison -Os?

[Kumar Gala <galak@kernel.crashing.org>]

On Aug 23, 2011, at 8:45 PM, Richard Purdie wrote:

> On Tue, 2011-08-23 at 20:32 -0500, Kumar Gala wrote:
>> If tinylogin is the only issue why modify/patch gcc?  I see we have
>> meta/recipes-core/tinylogin/tinylogin-1.4/use_O2_option.patch to deal
>> with this?
>> 
>> Not allowing -Os at all, which is our current situation on PPC is
>> problematic.  So trying to see if this issue is really limited to gcc
>> 4.5 or not.  How can I reproduce it with current poky.git?
> 
> We were seeing problems when makefiles were putting -Os into compiler
> flags without our knowledge. In some cases -Os was silently corrupting
> binaries. We therefore ended up adding the poison so if anything was
> using the option we knew to generate buggy code, we'd know about it.

So, I'm trying to figure out if it was just tinylogin or more that had issues.

> If we know gcc to be safe using that option we can drop the patch and
> users can enable it where it makes sense to them. I still don't like
> makefiles changing compiler optimisations from under us though. Last I
> heard, -Os was still very badly supported and not recommended by the gcc
> community.

That's a different issue altogether.  I think its bad that we dont allow -Os at all which is what I'm trying address and the fact that its pretty necessary to build u-boot because it has size limitations.

- k