Re: macOS/GCC support policy

[Eli Zaretskii]

> From: Philipp Stephani <address@hidden>
> Date: Fri, 2 Aug 2019 16:55:02 +0200
> Cc: Alan Third <address@hidden>, address@hidden, 
>       Emacs developers <address@hidden>
> 
> /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/objc/NSObject.h:22:4:
> error: unknown type name 'instancetype'
>    22 | - (instancetype)self;
>       |    ^~~~~~~~~~~~
> 
> (lots of similar errors follow)
> 
> This indicates that GCC treats the header as C instead of Objective C.
> Which is interesting because -x objective-c is given explicitly. Does
> GCC need some other flag to force compilation as Objective C?

Searching the Internet for this error seems to suggest that this SDK's
header files are supposed to be compiled only by clang, i.e. their GCC
compilation is deliberately broken by Apple.

Why does Emacs need AppKit/AppKit.h?  If this is for some important
functionality, and if we cannot find a compatible replacement, I guess
the conclusion is that we cannot build Emacs on macOS with GCC due to
the Apple system headers.