Intermittent CI issue: AssertionError: Unexpected stderr LLVM ERROR: IO failure on output stream: Broken pipe != #36388

Looks like there are new intermittent CI issues of the form AssertionError: Unexpected stderr LLVM ERROR: IO failure on output stream: Broken pipe !=.

Not sure when they started happening? Maybe after #36100?

It could make sense to try to reproduce/bisect and fix this upstream in LLVM and possibly temporarily use llvm 22?

Examples:

• https://github.com/bitcoin/bitcoin/actions/runs/36684426510/job/109787331885?pr=36033#step:11:25384
• https://github.com/bitcoin/bitcoin/actions/runs/36602839470/job/109524274533?pr=36383#step:11:3974

Not sure when they started happening? Maybe after #36100?

Possibly. There seem to be reports of similar failures, in different contexts, from at least Clang 21.x: https://github.com/llvm/llvm-project/issues/174173.

I guess this is halfway expected:

• Bitcoin Core ignores sigpipe:

src/init.cpp-939-    // Ignore SIGPIPE, otherwise it will bring the daemon down if the client closes unexpectedly
src/init.cpp:940:    signal(SIGPIPE, SIG_IGN);

• The llvm-symbolizer inherits that, and when asked for ubsan suppressions over a pipe, and when that pipe gets closed (by Bitcoin Core getting killed by the test), it falls back to printing that error.

So I guess this could just use a graceful termination instead of a kill?