This bug report might shed some light on this: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47460
I wonder if I've misunderstood the GCC docs at https://gcc.gnu.org/onlinedocs/gcc-4.9.1/gcc/_005f_005fsync-Builtins.html#_005f_005fsync-Builtins. My reading of the docs was that if the platform doesn't support the needed instructions then GCC will generated a call to e.g. __sync_fetch_and_add_1, where that function *is provided by GCC* as a fallback. Now I'm wondering if I'm supposed to supply that fallback. On Wed, Jul 16, 2014 at 9:32 PM, Páli Gábor János <pali.ga...@gmail.com> wrote: > 2014-07-16 20:57 GMT+02:00 Niklas Larsson <metanik...@gmail.com>: > > I get the same failure when I try to build HEAD. Turns out the error > occurs > > on the 32-bit Windows build, and my successful build was a 64-bit build. > My > > 64-bit build still succeeds. > > Perhaps you should specify -march=i586 for the C compiler? > > I have tried Johan's test program (posted in this thread earlier) with > -march=i386 and it generates a function call for > __sync_fetch_and_add_1(). (No cmpxchg?) In case of -march=i486, > __sync_fetch_and_add_8() is generated (this cpu type does have a > cmpxchg8b instruction). > > I faced this error earlier because the FreeBSD/i386 builder has been > failing for a while [1] as it assumes -march=i486 by default. With > -march=i586, everything builds just fine. On GNU/Linux, it is not a > problem as it builds C code with -march=i686. > > [1] http://haskell.inf.elte.hu/builders/freebsd-i386-head/317/10.html >
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