regression 1.50: Duplicate symbol linker error

[rylev]

In the latest crater run, a crate that compiles on 1.49, did not compile on 1.50 with a linker error you can see here.

@rustbot modify labels: +regression-from-stable-to-beta

[nagisa]

Seems like a not-genuine-regression, its just a case of cargo building and linking two different versions of the same crate (secp256k1), which appears to export no_mangle symbols if the error message looks right.

[wesleywiser]

Discussed in the release triage meeting. The above theory sounds plausible but we want to make sure there's not an actual issue here.

One possibility @Mark-Simulacrum mentioned is that our rules around no_mangle symbols being exported has changed somehow in this release. @petrochenkov do you happen to know if something like that has changed in this release?

[petrochenkov]

No, I didn't follow the no_mangle changes.

[apiraino]

Removing I-prioritize label as it looks this is on the radar along with the other crater run issues

[Mark-Simulacrum]

I can confirm this is a regression from 1.49. However, I'm having trouble bisecting this - nightlies seem to fail with the linker error for a while back; I ran bisect up to 2020-07-20.

Not sure what to do - maybe worth pinging cleanup group to try to minify at least.

[apiraino]

@rustbot ping cleanup