node:fs: calling writeFileSync/appendFileSync with negative 0 causes an assertion failure

[xunuwu]

Version

v26.8.1

Platform

Linux nixdesk 6.18.48 #1-NixOS SMP PREEMPT_DYNAMIC Fri Aug 28 06:22:54 UTC 2026 x86_64 GNU/Linux

Subsystem

fs

What steps will reproduce the bug?

require("node:fs").writeFileSync(-0, "")

or

require("node:fs").appendFileSync(-0, "")

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

it always happens on my machine. i have not tried on any other computer or os

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

for it to do the same thing as positive zero i assume

What do you see instead?

❯ echo 'require("node:fs").writeFileSync(-0, "")' | node -

  #  node[264400]: void node::fs::WriteFileUtf8(const v8::FunctionCallbackInfo<v8::Value>&) at ../../src/node_file.cc:2764
  #  Assertion failed: (*path) != nullptr

----- Native stack trace -----

 1: 0x629c801c0228  [node]
 2: 0x629c801c0b97 node::Assert(node::AssertionInfo const&) [node]
 3: 0x629c801cda7b  [node]
 4: 0x729babdcfae9 

----- JavaScript stack trace -----

1: writeFileSync (node:fs:2997:20)
2: [stdin]:1:20
3: runScriptInThisContext (node:internal/vm:219:10)
4: node:internal/process/execution:485:12
5: [stdin]-wrapper:6:24
6: runScriptInContext (node:internal/process/execution:483:60)
7: evalFunction (node:internal/process/execution:317:30)
8: evalTypeScript (node:internal/process/execution:329:3)
9: node:internal/main/eval_stdin:51:5
10: node:internal/process/execution:239:5


fish: Job 1, 'echo 'require("node:fs").writeF…' terminated by signal SIGABRT (Abort)

Additional information

No response

[christianaurichzm]

I was already digging into a similar fs fast-path issue when I saw this, so I took a look.

It seems to come from the JS isInt32() check accepting -0 while V8's IsInt32() does not. I also noticed that readFileSync(-0, 'utf8') hits the same mismatch in the read fast path.

I opened #65888 with a small fix for both cases.