Line-based breakpoints set dozens of unwanted ones

[jdm]

Debugging code from https://github.com/mozilla-servo/rust-mozjs/, if I set a breakpoint in gdb inside gc_callback in rust.rs I see messages like Breakpoint 2 at 0x408fad: rust.rs:70. (26 locations). This correctly breaks on the line, but trying to advance continues to break on the line each time in inlined code like transmute and borrow.

[michaelwoerister]

Good catch! I think I had a patch once that would turn off emitting source locations for inlined functions but it will probably be bit-rotted by now. I'll look into it next!

[michaelwoerister]

Can we try to come up with some minimal code to reproduce this behavior reliably? As @alexcrichton pointed out, it would be great to have an autotest before closing the issue.

[jdm]

fn bar() -> int {
    let s = Some(5).unwrap();
    s
}

fn main() {
    let _ = bar();
}

(gdb) b inline.rs:2
Breakpoint 1 at 0x404ebb: inline.rs:2. (2 locations)
(gdb) r
Starting program: /tmp/inline 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 1, inline::bar () at inline.rs:2
2       let s = Some(5).unwrap();
(gdb) n

Breakpoint 1, option::Option$LT$T$GT$::unwrap::he0fbfb416e1da23bIaa::v0.0 () at inline.rs:2
2       let s = Some(5).unwrap();
(gdb) n
inline::bar () at inline.rs:3
3       s
(gdb) q

[michaelwoerister]

Wow, that was quick :)
Thanks a lot!

[michaelwoerister]

At least for this example the issue seems to be fixed after PR #13441 has landed. I'll add this to the autotests next week and then, I think, we can close this issue.