GCC 4.8 has been released. C++-related improvements include the following highlights.

Language improvements:

• G++ now implements the C++11 thread_local keyword...
• G++ now implements the C++11 attribute syntax, e.g.
    [[noreturn]] void f();
  and also the alignment specifier, e.g.
    alignas(double) int i;
• G++ now implements C++11 inheriting constructors, e.g.
    struct A { A(int); };
  struct B: A { using A::A; }; // defines B::B(int)
  B b(42); // OK
• G++ now supports a -std=c++1y option for experimentation with features proposed for the next revision of the standard, expected around 2017. Currently the only difference from -std=c++11 is support for return type deduction in normal functions, as proposed in N3386.
• The G++ namespace association extension, __attribute ((strong)), has been deprecated. Inline namespaces should be used instead.

Standard library improvements:

Improved experimental support for the new ISO C++ standard, C++11, including:

• forward_list meets the allocator-aware container requirements;
• this_thread::sleep_for(), this_thread::sleep_until() and this_thread::yield() are defined without requiring the configure option --enable-libstdcxx-time;
• SSE optimized normal_distribution and simd_fast_mersenne_twister_engine.
• Use of hardware RNG instruction for random_device on new x86 processors (requires the assembler to support the instruction.)