DWARF does not emit DW_TAG_label

[ratmice]

In the following rust code it would be nice if this emitted a DW_TAG_label

fn foo() {
    'rs_label: {
        break 'rs_label;
    }
}

In the equivalent C code,

int main() {
  c_label:
    return 0;
}

This will emit a DW_TAG_label

 <2><55>: Abbrev Number: 3 (DW_TAG_label)
    <56>   DW_AT_name        : (indirect string, offset: 0): c_label

Meta

rustc --version --verbose:

rustc 1.88.0-nightly (cb31a009e 2025-04-27)
rustc 1.86.0 (05f9846f8 2025-03-31)

[moxian]

The label information does not exist in the MIR presently AFAICT, so adding that would probably be the first step
@rustbot label: -C-bug +C-enhancement +T-compiler +A-debuginfo +A-MIR

[bjorn3]

What would be the benefit of emitting this? Adding unnecessary things to the debuginfo still increases the size of the debuginfo and it already is way too big.

[ratmice]

It allows you to set breakpoints on labels, in the c example you can break main:c_label in gdb,
the gdb linespec processor would need fixing to deal the with quote in rust labels, but it is probably reasonable to escape it.

Edit:
In that sense it allows you to avoid specifying line numbers for stable breakpoints: instead of break main.rs:3 or whatever.

There is another way to do this, using https://crates.io/crates/probe and specifying a breakpoint on a probe.
But that only works in userspace on platforms that support probes.