"invalid subrange count" compiling `[(); 1 << 63]` with -g enabled

[ollie27]

The following produces an LLVM error with -g enabled:

let _a = [(); 1 << 63];

The error is:

invalid subrange count
!16 = !DISubrange(count: -9223372036854775808)
LLVM ERROR: Broken function found, compilation aborted!

[nagisa]

cc @michaelwoerister

[michaelwoerister]

Thanks for the bug report!

[cristicbz]

I've also hit this (with similar code), but in my case the "invalid subrange count" message showed up, but the code still compiled and passed the tests. Not sure if it's miscompiled or not.

Edit: Obviously this didn't crash because llvm assertions are disabled in stable. Yeah, still an important question around: is the code at risk of being miscompiled?

[tromey]

Yeah, still an important question around: is the code at risk of being miscompiled?

The error comes from the debuginfo verifier, so I think at worst you'd see invalid or incorrect DWARF.