FreeBSD 将会抛弃 gcc, 转而使用Apple的LLVM/Clang 。

FreeBSD 10 To Use Clang Compiler, Deprecate GCC

Posted by Michael Larabel on May 12, 2012

As indicated by the Q1-2012 FreeBSD Status Report, LLVM'sClang compiler is quickly replacing GCC for this popular BSD operating system.The developers are also making much progress in a GNU-free C++11 stack. ForFreeBSD 10 they're aiming for Clang as the default C/C++ compiler, deprecateGCC, and to have a BSD-licensed C++ stack. 

While the Q1-2012 FreeBSD Status Report was just talked about in theafore-linked article, the Clang and C++ items warranted their own more detailedarticle. 

Going back to 2009, FreeBSD developers have worked to replace GCC withLLVM/Clang. Over time, there's been numerous improvements especially with the FreeBSD 9.0 release. The FreeBSDdevelopers are interested in doing away with the GPL-licensed GNU CompilerCollection and instead use the Apple-sponsored LLVM/Clang work that's under aBSD-like license. 

As reported in the status report for the last quarter, Clang 3.0 is nowinstalled by default for FreeBSD 10.0-CURRENT and 9.0-STABLE. They're alsoworking to import a newer Clang snapshot since LLVM 3.1 and Clang 3.1 are about to be released (next week). OnFreeBSD 10.0-CURRENT, Clang can now build world and the generic FreeBSD kernelwithout emitting any error warnings. With more recent revisions, a new WITH_CLANG_IS_CC optionwill make Clang become the default cc, c++, and cpp commands. 

The intent is to make Clang become the default compiler for FreeBSD 10.0 and tothen deprecate GCC from FreeBSD. "The intent is to switch on this optionby default rather sooner than later, so we can start preparing for shipping10.0-RELEASE with Clang as as the default system compiler, and deprecating gcc." 

Additional information on building FreeBSD with Clang is available from this FreeBSD.org Wiki page. Any FreeBSD package notbuilding under Clang should be treated as a bug; "One of the most importanttasks at the moment is to actually build and run your entire FreeBSD systemwith Clang, as much as possible. Any compile-time or run-time problems shouldbe reported to the appropriate mailing list, or filed as a PR. If you havepatches and/or workarounds, that would be even better." 

There's also been other non-Apple operating systems toying with Clang fordifferent use-cases. There was also the Debian Clang experiment, which could buildmost of the Debian packages for popular architectures, but LLVM/Clang stillfalls behind in its support of the more obscure CPU architectures and platformscompared to GCC. Some vendors have also been playing around with the idea of usingClang to build the Linux kernel (it's possible to do withcertain kernel configurations, patches, and other headaches). 

LLVM/Clang is unlikely to replace GCC on any tier-one Linux distribution as thedefault in the foreseeable future, but it's interesting as a complementaryoption. Clang is quite good with its static analysis abilities, among other benefits. 

In terms of FreeBSD's mission for a GNU-free C++11 stack, the libc++ andlibcxxrt libraries have gained new features, support for the ARM EABI, and withClang 3.1 can now pass all C++11 atomic tests. The libcxxrt library is the new C++ run-time that was given by PathScale.There's still some work ahead in this area, but the status report mentions,"we're on track for a BSD licensed C++ stack in 10.0."

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