CARGO_INCREMENTAL breaks debuginfo

[sophiajt]

In the same project, if I compile with CARGO_INCREMENTAL=1 and run the application through lldb, I get:

$ lldb target/debug/hello
(lldb) target create "target/debug/hello"
Current executable set to 'target/debug/hello' (x86_64).
(lldb) b main
Breakpoint 1: where = hello`main, address = 0x00000001000141d0

Same project without:

$ lldb target/debug/hello
(lldb) target create "target/debug/hello"
Current executable set to 'target/debug/hello' (x86_64).
(lldb) b main
Breakpoint 1: 2 locations.

The latter, I believe, is what we want as it's what you'd get by hand when using rustc. With incremental turned on, we can't easily step into the original source. Instead, we end up stepping through the assembly.

[sophiajt]

cc @michaelwoerister and @nikomatsakis

[michaelwoerister]

Is this on OSX? If so this might be the same problem as rust-lang/rust#39160.

[sophiajt]

Yes, this on macOS Jonathan

…

_____________________________ From: Michael Woerister <notifications@github.com<mailto:notifications@github.com>> Sent: Friday, April 7, 2017 9:00 PM Subject: Re: [rust-lang/cargo] CARGO_INCREMENTAL breaks debuginfo (#3905) To: rust-lang/cargo <cargo@noreply.github.com<mailto:cargo@noreply.github.com>> Cc: Jonathan Turner <jturner@mozilla.com<mailto:jturner@mozilla.com>>, Author <author@noreply.github.com<mailto:author@noreply.github.com>> Is this on OSX? If so this might be the same problem as rust-lang/rust#39160<rust-lang/rust#39160>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#3905 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AAhZVqf55Y3OJzTbuhLNht9UqH-VfWPIks5rtfs8gaJpZM4M2buK>.

[nikomatsakis]

@jonathandturner care to try and narrow it down by building w/o incremental, but w/ codegen-units?

[nikomatsakis]

eg, by setting RUSTFLAGS="-Zcodegen-units=256" or something; I guess it' snot clear what setting would do it, but something big is likely to work :)

[sophiajt]

@nikomatsakis - yes, I can confirm the -Ccodegen-units=256 causes the same issue.

[sophiajt]

Closing as a dupe of rust-lang/rust#39160

(plz fix kthx 😄)