[PATCH] D15455: [Driver] Let -static override the toolchain default PIC setting.

[Joerg Sonnenberger via cfe-commits]

On Fri, Dec 18, 2015 at 12:45:47PM -0800, Bob Wilson via cfe-commits wrote:
> 
> > On Dec 17, 2015, at 10:59 AM, Bob Wilson via cfe-commits <cfe-commits at lists.llvm.org> wrote:
> > 
> > 
> >> On Dec 17, 2015, at 10:16 AM, Joerg Sonnenberger via cfe-commits <cfe-commits at lists.llvm.org> wrote:
> >> 
> >> On Wed, Dec 16, 2015 at 11:59:10PM +0000, Bob Wilson via cfe-commits wrote:
> >>> We can change this to be Darwin-specific if you prefer, but we should
> >>> maintain compatibility with GCC and previous Clang releases in this behavior.
> >> 
> >> Who is really affected by this? I don't care too much about obscure
> >> Darwin hacks, but I really wonder why it isn't better to just explicitly
> >> add -fno-PIC (e.g. when building a kernel module). It's not like that
> >> will break on older versions of GCC or Clang.
> > 
> > Apple has internal projects that are failing to build. This behavior has been in places for many years and I don’t even know how we could find all the people relying on this behavior. Yes, we could break them and force everyone to add -fno-PIC, but typically when we make disruptive and incompatible changes like that, we need to stage the changes and give people a transition plan. For example, we could keep the old behavior but add a warning about the change, something like “warning: -static may be changed in future versions of clang to stop implying -fno-PIC”. After a year or two, we could then go ahead with the change. That is all a lot of work and there needs to be some significant benefit to justify breaking compatibility with older compilers. I don’t see any significant benefit here. It’s a 2-line change to the driver.
> 
> Joerg, I’m going to interpret your “I don’t care too much” comment as
> an indication that you’re not opposed to moving forward with the
> Darwin-specific change to restore the previous behavior. I went ahead
> and committed the change in r256026.

Correct.

> I can also add another data point on the impact. We just spent several
> days tracking down a problem that turned out to be caused by this. The
> code built successfully but crashed at run-time. It was extremely
> difficult to figure out what was going wrong.

OK, nasty. I'd like to see the warning suggested above at some point :)

Joerg