Clang as default compiler November 4th

[Please confine your replies to toolchain_at_freebsd.org to keep the thread
on the most relevant list.]

For the past several years we've been working towards migrating from
GCC to Clang/LLVM as our default compiler.  We intend to ship FreeBSD
10.0 with Clang as the default compiler on i386 and amd64 platforms.  To
this end, we will make WITH_CLANG_IS_CC the default on i386 and amd64
platforms on November 4th.

What does the mean to you?

 * When you build world after the default is changed /usr/bin/cc, cpp, and
   c++ will be links to clang.

 * This means the initial phase of buildworld and "old style" kernel
   compilation will use clang instead of gcc.  This is known to work.

 * It also means that ports will build with clang by default.  A major
   of ports work, but a significant number are broken or blocked by
   broken ports. For more information see:
     http://wiki.freebsd.org/PortsAndClang

What issues remain?

 * The gcc->clang transition currently requires setting CC, CXX, and CPP
   in addition to WITH_CLANG_IS_CC.  I will post a patch to toolchain_at_
   to address this shortly.

 * Ports compiler selection infrastructure is still under development.

 * Some ports could build with clang with appropriate tweaks.

What can you do to help?

 * Switch (some of) your systems.  Early adoption can help us find bugs.

 * Fix ports to build with clang.  If you don't have a clang system, you
   can use the CLANG/amd64 or CLANG/i386 build environments on
   redports.org.

tl;dr: Clang will become the default compiler for x86 architectures on 2012-11-04

-- Brooks