https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84568
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:3fc22eedb033cbff1bf5a70c6a032d3c5ce2d867 commit r12-8161-g3fc22eedb033cbff1bf5a70c6a032d3c5ce2d867 Author: Palmer Dabbelt <pal...@rivosinc.com> Date: Thu Apr 14 17:22:58 2022 +0100 libstdc++: Default to mutex-based atomics on RISC-V The RISC-V port requires libatomic to be linked in order to resolve various atomic functions, which results in builds that have "--with-libstdcxx-lock-policy=auto" defaulting to mutex-based locks. Changing this to direct atomics breaks the ABI, this forces the auto detection mutex-based atomics on RISC-V in order to avoid a silent ABI break for users. See Bug 84568 for more discussion. In the long run there may be a way to get the higher-performance atomics without an ABI flag day, but that's going to be a much more complicated operation. We don't even have support for the inline atomics yet, but given that some folks have been discussing hacks to make these libatomic routines appear implicitly it seems prudent to just turn off the automatic detection for RISC-V. libstdc++-v3/ChangeLog: * acinclude.m4 (GLIBCXX_ENABLE_LOCK_POLICY): Force auto to mutex for RISC-V. * configure: Regenerate.
