On Tue, Mar 17, 2020 at 05:35:13PM -0400, Reinhard Tartler wrote: > Control: forwarded -1 aspectc-develop...@aspectc.org > > Hi Adrian, > > Olaf, the upstream developer, has a question regarding your patch to > aspectc++. > Would you mind having a look and ideally sharing your reply to everyone? > > Thank you! > -rt > > On 3/17/20 11:05 AM, Olaf Spinczyk wrote: > > Hi Reinhard! > > > > Do you understand the reasons behind the patch? > > > > The difference is the following addition for linking: > > > > -Wl,--as-needed -latomic -Wl,--no-as-needed > > > > (1) I wonder why the atomics (e.g. __atomic_fetch_add_4) are not > > available by default in armel. They seem to be on most other platforms.
Most other platforms have processor instructions for atomics. Older arm processors do not,[1] they are implemented with a kernel helper. It is a bug in gcc that linking with libatomic is not done automatically: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81358 > > (2) Why is "--as-needed ... --no-as-needed" necessary? It is not necessary. It avoids linking with libatomic when it is not needed on other platforms. > > (3) Could -latomic also be placed at the end of the list of libraries > > (behind the additional libraries needed for Clang 9.0.x)? The further behind the better, it has to come after static libraries using it. > > Cheers, > > > > Olaf cu Adrian [1] The Debian armel port currently has a port baseline of armv5, the Debian armhf port (including the raspbian rebuild) target more recent processors with atomic instructions.
