LTO enabled built `node` binary doesn't exit

[richardlau]

Version

v17.0.0-pre

Platform

Linux b4436f7227be 4.18.0-240.10.1.el8_3.x86_64 #1 SMP Wed Dec 16 03:30:52 EST 2020 x86_64 GNU/Linux (the gcc:11 container)

Subsystem

No response

What steps will reproduce the bug?

./configure --enable-lto --ninja
ninja -C out/Release
out/Release/node -p process.versions

How often does it reproduce? Is there a required condition?

Every time

What is the expected behavior?

Node.js prints the contents of process.versions and exits.

What do you see instead?

Contents of process.versions is printed but the process does not exit.

Additional information

Doesn't happen with regular non-LTO builds.

I've been testing inside the gcc:11 container (following the steps in /~https://github.com/nodejs/node/blob/master/.github/workflows/daily.yml). Please note that the build is succeeds but the GitHub workflow doesn't attempt to run the built binary (or run any tests). Interestingly the repl will exit but running scripts or tests does not.

Use of ninja isn't the issue -- the problem replicates if building with make.

Earlier versions of gcc can't build Node.js with LTO enabled (see #38570).

AFAICT this also occurs with the current v16.x-staging (e.g. before the V8 9.4 update). I haven't gone back any further yet.

[richardlau]

Problem exists all the way back to Node.js 16.1.0.

Node.js 16.0.0 fails to compile with --enable-lto.

/usr/bin/ld: /tmp/ccB2LnG9.ltrans53.ltrans.o: in function `cppgc::internal::MarkerBase::VisitRoots(cppgc::EmbedderStackState)':
<artificial>:(.text+0xafa7): undefined reference to `PushAllRegistersAndIterateStack'
/usr/bin/ld: /tmp/ccB2LnG9.ltrans54.ltrans.o: in function `heap::base::Stack::IteratePointers(heap::base::StackVisitor*) const':
<artificial>:(.text+0x1486): undefined reference to `PushAllRegistersAndIterateStack'
collect2: error: ld returned 1 exit status

[kasicka]

Little off topic, but would it make sense to have LTO label?

[danbev]

This issue only happens when Node.js is configured with --enable-lto and only for Release builds, not for Debug builds. The issue seems to be that there is an active libuv handle that is causing the event loop to block, hence the process not exiting/hanging.

This debugging session contains details about this issue and for those how don't want to read through all of that the summary is that GCC LTO was generating some incorrect code (not blaming GCC, or anyone else for that matter) which was causing this issue. After some investigating the issue pointed me to libuv/libuv#2588 and adding -fno-strict-aliasing to Node.js libuv build and the correct code is generated also for LTO builds and this issue is gone. I'll open a PR shortly for this.