Re: [gentoo-user] lazy gcc switching

[Bill Longman <bill.longman@gmail.com>]

On 07/21/2010 03:22 AM, Dale wrote:
> Alan McKinnon wrote:
>> On Wednesday 21 July 2010 10:53:19 fajfusio@wp.pl wrote:
>>   
>>> Hi
>>>
>>> I've just switched to gcc 4.3.4 from 4.1.2 using gcc-config tool. I
>>> don't
>>> want to rebuild any package now. As time goes on my packages will be
>>> compiled with new version. I hope that after a few month there will be
>>> only a number of packages not compiled with a new gcc. Then I want to
>>> recompile them on demand including libtool if necessary.
>>>
>>> Do you think my plan have a chance to succeed.
>>>      
>> Yes.
>>
>> Why do you think you would even need to get into a long compile? Have
>> you been
>> reading that GCC Upgrade Guide at gentoo.org? You know, the one that
>> is so
>> flat out wrong on so many levels?
>>
>>    
> 
> I recently upgraded my gcc and I must confess, I did do a emerge -e
> system.  Is it needed, nope.
> 
> OP, Alan is correct on this.  You don't really need to re-emerge
> everything.  If, like me, you want to be on the safe side, just do a
> emerge -e system and let the rest recompile as you update.
> 
> Another good thing about this way, if this version of gcc causes you
> trouble, you can downgrade and only have to re-emerge system.  ;-)   I
> did upgrade gcc once and had serious issues with it.  Wouldn't compile a
> kernel, programs crashing and other weird things.  After a downgrade,
> all went back to normal.  The only thing worse than a emerge -e world is
> having to do it twice.  LOL

And to play devil's advocate, I'll chime in with my experience. The 4.4
GCC, at least on AMD CPUs, creates noticeably faster code. I recompiled
all my packages after I upgraded to 4.4 and it was a *noticeable*
difference.

But, to make perfectly clear what Alan and Dale have stated previously,
it is not a requirement to recompile anything. The binaries that are
created still call the same system calls as they did before. The kernel
still publishes them in the same locations. And to prove to yourself
this is true, grab a statically linked binary, compiled for a stock
standard i686, and run it on your machine.