illegal instruction crash in rust 1.78

[amircodota]

Since rust 1.78, windows produced binaries have a dependency on the api-ms-win-core-synch-l1-2-0.dll which seems to be missing on some installations of windows 10 and 11.

We've had reports from users of our binary that our latest version fails with error 0xc000001d

[veera-sivarajan]

@rustbot label -needs-triage +O-windows +A-linkage

[ChrisDenton]

I doubt this is a linkage issue as 0xc000001d is STATUS_ILLEGAL_INSTRUCTION. Meaning that an attempt was made to execute an illegal CPU instruction. See NTSTATUS values.

[amircodota]

Hmmm.... could this be that the missing DLL causes this issue? Like trying to jump to address 0x0?

Here's what I know -

1. Rust 1.78 added the dependency on this DLL. Before 1.78, this dependency did not exist.
2. On the machines in question, Dependency Walker shows only this specific dll is missing.

I am now build a new binary with rust 1.77.2. Will distribute it and report back if it fixed the issue or not

[ChrisDenton]

api-ms-win-core-synch-l1-2-0.dll is not a real DLL, it's an "api set". Windows will automatically redirect it to the real DLL. I strongly suspect that is not the issue, not least because it's listed by the documentation (e.g. https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-wakebyaddressall) and used by Synchronization.lib.

If you can use an affected machine directly then you could try using windbg to see what instruction is causing this.

[amircodota]

@ChrisDenton I'm not that familiar with windbg and native code debugging, but if you can provide instructions, I'll see if my user agrees to try it :-)

[ChrisDenton]

Ah, that might be more complicated. Can you get a backtrace from them? And their CPU information, if possible?

If they did want to have a go at windbg, it can be downloaded from here and there's a tutorial. However, it should be relatively simple in this case. You just run windbg and, from the file menu, click "Launch Executable" then find the exe to run. After that you just click the green "Go" button and when the exe crashes it should highlight the offending instruction in yellow.

[amircodota]

A quick update - I heard back from the user and it seems downgrading to rust 1.77.2 fixed the issue.
Not sure if it is related to the missing DLL or not, but I'll try to keep digging.

[amircodota]

Here's the output from windbg. Hope it helps narrow it down :-)

[bjorn3]

ud2 is an instruction that allows a program to intentionally crash. What is the function name of the function at TabNine_fa79b5ff476d1afe+0x95a5a8?

[amircodota]

can you guide me on how to figure this out?

This exe is compiled using x86_64-pc-windows-gnu with profile production

[profile.production]
inherits = "release"
lto = true