[LLVMdev] Darwin option processing

[Mike Stump]

On May 8, 2009, at 1:02 PM, Chris Lattner wrote:
> This goes against our general direction for llvm libraries: they  
> should generally all be built pic.

After reviewing yet more of the Makefile,rules file, I believe  
ENABLE_PIC is the right thing to check.  Currently ENABLE_PIC has to  
be set to get shared bits built, if the user wants them.  Given that,  
we can use that to control wether or not -mdynamic-no-pic is added.   
Because this _must_ be set, it is safe to use the setting of that flag  
to make the decision on wether to add -mdynamic-no-pic.  If that flag  
isn't set, the resulting objects, in general, can't be used in a  
shared library.

> This is because we don't know how they will be linked in.

Currently, the Makefile does know how the object will be used.  On  
darwin, -fno-common is only added when ENABLE_PIC is 1, and objects  
can't be used in a shared library unless -fno-common is added.