Re: userland atomics

[jnemeth%victoria.tc.ca@localhost (John Nemeth)]

On May 4,  2:39pm, Matt Thomas wrote:
} On Dec 12, 2008, at 6:58 PM, John Nemeth wrote:
} 
} >      Do we have any kind of atomic operations in userland?  I'm  
} > working
} > with Asterisk 1.6.0.1 on NetBSD 5.99.3.  Its configure script trys to
} > link this program (along with a lot of #define):
} >
} > int
} > main ()
} > {
} > int foo1; int foo2 = __sync_fetch_and_add(&foo1, 1);
} >   ;
} >   return 0;
} > }
} >
} > For some reason, the corfigure script believes that it is successful;
} > however, linking of Asterisk fails later due to a missing symbol.
} 
} That's because in a gcc later than ours that becomes a builtin to gcc.

     Supposedly it trys to link that.  It should fail at configure
time.  The configure.ac snippet is:

AC_MSG_CHECKING(for compiler atomic operations)
AC_LINK_IFELSE(
AC_LANG_PROGRAM([], [int foo1; int foo2 = __sync_fetch_and_add(&foo1, 1);]),
AC_MSG_RESULT(yes)
AC_DEFINE([HAVE_GCC_ATOMICS], 1, [Define to 1 if your GCC C compiler provides at
omic operations.]),
AC_MSG_RESULT(no)
)

} What you want to look at is atomic_ops(3).

     I'll keep that in mind.  Right now, I just want to get it working.

}-- End of excerpt from Matt Thomas