Richard Earnshaw <rearn...@arm.com> writes: > Older versions of the Arm architecture lack support for __sync > operations directly in hardware and require calls into appropriate > operating-system hooks. But such hooks obviously don't exist in a > freestanding environment. > > Consquently, it is incorrect to assume during configure that such > functions will exist and we need a configure-time check to determine > whether or not these routines will work. > > libbacktrace: > > * configure.ac: Always check if the compiler supports __sync > operations. > * configure: Regenerated. > --- > > A consequence of this assumption that these functions 'just work' (TM) > is that we build libbacktrace with threading support, but that then > fails at link time when we find out that they do not. I'm not sure I > really understand why we can assume that having with_target_subdir set > is enough to assume that the operations exist: it isn't for Arm and it > looks like it wasn't for hpux either. Perhaps the whole logic here > needs reconsideration...
My understanding was that libatomic would provide implementations of the __sync operations where required. I guess that is not always the case, though I don't understand why that should be. In any case, this patch is fine. Thanks. Ian
