Broken perf map when newline in RegExp with Node24

[GuillaumeLagrange]

Version

24.7.0

Platform

$ uname -a
Linux badlands 6.12.70 #1-NixOS SMP PREEMPT_DYNAMIC Wed Feb 11 12:40:29 UTC 2026 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

// repro.js
const re = new RegExp("HELLO\nWORLD", "sy");
const str = "HELLO\nWORLD";
for (let i = 0; i < 100_000; i++) {
  re.lastIndex = 0;
  re.exec(str);
}

Note: A hot loop (100_000 iterations) is required to trigger JIT compilation of the RegExp, else the symbol is not present in the perf map.

node --perf-basic-prof repro.js
Then look for HELLO in the outputted /tmp/perf-<pid>.map

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

Always

What is the expected behavior? Why is that the expected behavior?

Node 22 output (correct):

7f7035fc5ec0 358 RegExp:HELLO\nWORLD

What do you see instead?

Node 24 output (broken, on multiple line):

7f2306002980 358 RegExp.> src: 'HELLO
WORLD' flags: 'sy'

Additional information

I did not find any spec for these file except for https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt

This seems to corroborate the fact that each symbol should be a single line, and newline should be escaped

[himself65]

Looks like a v8 issue, open an issue on upstream: https://issues.chromium.org/issues/490381618

[Renegade334]

The fix for this (v8/v8@7b7365d) is a non-trivial set of changes to the regexp engine, which doesn't translate directly to the versions of the regexp internals present in v25 and earlier. It will cherry-pick to v26 without any issue, but I suspect that the ratio of bug size to amount of hacking required will preclude this from being backported.