[patch libstdc++] Optimize synchronization in std::future if futexes are available.

[Sandra Loosemore]

Re:

> On 17/01/15 01:45 -0500, Hans-Peter Nilsson wrote:
>> On Fri, 16 Jan 2015, pinskia@gmail.com wrote:
>>> > On Jan 16, 2015, at 9:57 PM, David Edelsohn <dje.gcc@gmail.com> wrote:
>>> >
>>> > This patch has broken bootstrap on AIX
>>> >
>>> > May I mention that this really should have been tested on systems
>>> > other than x86 Linux.
>>>
>>> It also broke all newlib targets too. So you could have tested one listed in the sim-test web page.
>>
>> For those interested, PR64638.
>
> Should be fixed in trunk now, by this patch.

I'm now getting this error in an arm-none-linux-gnueabi cross build:


In file included from 
/scratch/sandra/arm-fsf2/obj/gcc-mainline-0-arm-none-linux-gnueabi-i686-pc-linux-gnu/arm-none-linux-gnueabi/libstdc++-v3/include/future:44:0,
                  from 
/scratch/sandra/arm-fsf2/src/gcc-mainline/libstdc++-v3/src/c++11/functexcept.cc:34:
/scratch/sandra/arm-fsf2/obj/gcc-mainline-0-arm-none-linux-gnueabi-i686-pc-linux-gnu/arm-none-linux-gnueabi/libstdc++-v3/include/bits/atomic_futex.h:71:3: 
error: #error We require lock-free atomic operations on int
  # error We require lock-free atomic operations on int
    ^

It used to work a few days ago....  nothing changed in my build 
environment except that I did "svn up" in my gcc source directory....

-Sandra