[arch-general] makepkg.conf CFLAGS

[LoneVVolf]

On 01-06-14 14:03, Yamakaky wrote:
> Hi
>
> I just discovered the gcc option march=native. It enables all the 
> local-supported optimizations, without downsides except the 
> non-portability of the binaries. Is there a reason why it isn't 
> enabled by default, as cross platform compilation isn't used by most 
> of the users (I think) ?
>
> Yamakaky

Yamakaky, the non-portability is a very big downside imo.

When using -march=native on a core i7, those packages won't run on an 
amd processor or on an intel atom. They  might even give problems on a 
core i3.


All official packages for arch are build on systems running arch.
With current makepkg default, all packages build will run on all systems 
with same architecture (x86-64 / i686) .
Now assume makepkg had -march=native as default.
packages build for official repos now will fail on all systems that 
don't have same cpu family.
This effectively forces all devs to change makepkg defaults.
Incase they forget it, their offficial build will fail.

some user-specific examples :
user has a netbook with an intel atom processor and needs to compile 
program foo to work on it.
building foo on the netbook takes over an hour.
User tries building foo on his main system with a core i7, SSD etc and 
finds building foo takes only a few minutes there. foo build with 
makepkg default on the i7 will run flawlessly on the netbook.


user has an ageing AMD FX system and wants to replace that with an intel 
core i7 system.
they don't feel like re-installing, so just transfer the harddrive to 
the intel system.
if they used -march=native everything they build on the AMD FX system 
will need to be rebuild on the core i7 .

LW