[cfe-dev] [PATCH] Added support to libc++ for GCC 4.3, GCC 4.5, and most recent head of Clang.

[Jesse Towner]

Okay, please disregard the original patch, there were some bugs that
came up when I ran the test suite on OS X with GCC 4.2.1. This patch
should take care of them.

Just to recap, I've tested it now on GCC 4.3.4, GCC 4.4.3, GCC 4.5.1,
GCC 4.6 (head), and Clang/LLVM 2.8 (head) with and without-std=c++0x on
Ubuntu 10.04 x86-64; GCC 4.2.1 and Clang/LLVM 2.8 (head) on OSX 10.6.4
(both i386/x86-64); and GCC 4.2.1 on iOS 4.0.1 (both ARMv6/ARMv7).

Remarkably, many of the tests built and passed with Clang/LLVM 2.8 on
OSX, although not quite as many as GCC was able to handle.

I had to add an additional tweak to the cmath header for OSX when
building with Clang with -std=c++0x, as that flag disables the GNU
extensions mode and defines __STRICT_ANSI__, and the current math.h
headers with OSX/iOS (Xcode 3.2.3) don't bring in a number of the C99
math functions when __STRICT_ANSI__ is defined.

Here's the revised change list:

- Better C++0x feature detection for both GCC and Clang (using Clang's
__has_feature builtin preprocessor macro). Added explicit detection for
defaulted and deleted functions.
- Fix for Clang compilation error: Changed __config header to recognize
Clang's support for builtin unicode character types char16_t and
char32_t.
- Fix for Clang compilation error: #undef'd __STRICT_ANSI__ in cmath on
Apple platforms to get all C99 function symbols pulled in. Used clang's
new push_macro/pop_macro pragmas to restore __STRICT_ANSI__ afterward.
- Fixes for GCC 4.3: Moved a lot of the GCC 4.3 C++0x feature support up
to 4.4 for now in __config header, as although they exist in 4.3,
various parts of libc++ assumed that they were fully implemented or
implied the existence of other C++0x features. Also fine-tuned some
preprocessor conditional checks in iterator, memory, thread, type_traits
and utility headers to account for this. It'd probably be possible to
rewrite a bunch of the offending areas (things that use variadic
templates and auto/decltype) so that they could work in 4.3.
- Fix for GCC 4.5 compilation error: Added conditional operator
overloads for comparing generic pointer types against nullptr_t to
handle stricter/more fickle template argument type matching in this
compiler.
- Fix for GCC 4.5 compilation error: Changed both std::move and
std::forward C++0x-specific implementations to explicitly cast the
object to an r-value reference type as GCC 4.5 implements the new
wording for move semantics and rvalue references
(http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3053.html).
This didn't introduce warning messages in any of the other compilers I
tested with, so not sure what compiler was originally causing the issues
here.
- Fix for GCC 4.6: Changed libc++ to use GCC 4.6's builtin nullptr
keyword.

Cheers,

Jesse
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