RFC - Remove support for PCH post 4.8

[Chris Lattner]

On Nov 27, 2012, at 11:05 PM, Xinliang David Li <davidxl@google.com> wrote:

> On Tue, Nov 27, 2012 at 10:40 PM, Chris Lattner <clattner@apple.com> wrote:
>> 
>> On Nov 27, 2012, at 9:08 PM, Miles Bader <miles@gnu.org> wrote:
>> 
>>> Chris Lattner <clattner@apple.com> writes:
>>>> Clang has fantastic support for PCH... and soon modules.  We don't
>>>> plan to drop PCH support when modules is implemented.
>>> 
>>> Do you have a pointer to the modules proposal clang will implement?
>> 
>> Most of it is implemented in mainline Clang already.
> 
> For Object-C or C++?

C and Objective-C are nearly complete, C++ support is still in progress.

> 
>> Here is a recent talk describing it:
>> http://llvm.org/devmtg/2012-11/Gregor-Modules.pdf
>> 
> 
> It is likely that the module file format will be standardized in the
> future, so it is better for different communities to start move in the
> same direction. Is the module format adopted by Clang documented
> anywhere?

No, the design does not require a binary compatible file format.  Header files and module maps remain "the truth".  Any binary file format produced by a compiler as a side effect of building is an implementation detail of that compiler.

-Chris