I've been stuck for a few days on a problem with linking clangd-fuzzer getting OoM killed right at the end of buildPhase 18 hours into the clang build. Even -j1 isn't enough.
I tried useMoldLinker, but that's broken right now (due to something not putting NIX_CFLAGS_LINK under env?).
Then I tried updating the system again, but now useMoldLinker causes eval to overflow the stack.

Has anyone found a reasonable solution to building clang (LLVM 20 and 21) without needing ludicrous amounts of memory?
If push comes to shove I could perhaps suffer a larger swap file...

For reference:

[nixos@nixos:~/system]$ free -h
               total        used        free      shared  buff/cache   available
Mem:           7.7Gi       6.0Gi       105Mi          0B       1.6Gi       1.5Gi
Swap:           15Gi       152Mi        15Gi

(There is high memory usage right now because it's in the middle of retrying clang.)

I had a build almost ending already, and this is what the RSS looked like just within 10s of the OoM kill:

436704 bin/c-index-test
4203668 bin/clang-tidy
2798596 bin/clangd-fuzzer

So yeah I think --cores 1 is worth a try, though it'll probably take over 2 days to build a single clang version (and I need 2). 🫠

In reply to @misuzu:matrix.org
https://riseproject.dev/2026/03/24/announcing-the-rise-risc-v-runners-free-native-risc-v-ci-on-github/

ld.mold: line 292: 8914 Killed

Not even mold can handle it (--cores 4). Time to suffer the 6-day long --cores 1 build.

System rebuild is finally done.
My u-boot env was so scuffed that the new version didn't boot.
I flashed the latest version of u-boot, reset the env, and now it boots.

[root@nixos:~]# uname -a
Linux nixos 6.19.8 #1-NixOS SMP PREEMPT Fri Mar 13 16:26:05 UTC 2026 riscv64 GNU/Linux

[root@nixos:~]# nixos-version
26.05.20260316.b0515cb (Yarara)