Incorrect HashMap visualization in WinDbg

[nanguye2496]

I tried to debug this program in WinDbg.

use std::fmt;

#[derive(PartialEq, Eq, Hash)]
struct Student {
    name: String,
    country: String,
}

impl fmt::Display for Student {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.name, self.country)
    }
}

fn main() {
    use std::collections::HashMap;
    let mut map = HashMap::new();
    let s1 = Student { name: String::from("Tom"), country: String::from("UK") };
    let s2 = Student { name: String::from("Alex"), country: String::from("US")};
    map.insert(s1, 10);
    map.insert(s2, 8);
    for (k,v) in map.iter() {
        println!("{}, {}", k, v);
    }
}

When examining the variable map in WinDbg, I got this visualization:

The screenshot illustrates two problems:

• The Name column displays meaningless numeric values (0x0, 0x1) instead of the keys.
• The Value column displays error messages instead of the values.

These two problems are filed under the same bug report since I've discovered that they can both be tied to the same cause - WinDbg's failure to perform the casting of base.table.ctrl.pointer to tuple<$T1, $T2>* in HashMap's natvis entry.

<Item Name="{((tuple&lt;$T1, $T2&gt;*)base.table.ctrl.pointer)[-(i + 1)].__0}">((tuple&lt;$T1, $T2&gt;*)base.table.ctrl.pointer)[-(i + 1)].__1</Item>

Meta

This bug is discovered on rustc 1.52.0-dev and WinDbg debugger engine version: 10.0.21306.10

[nanguye2496]

I've attempted to remove the whitespace between $T1 and $T2. This fix does yield the correct visualization on WinDbg, but makes VSCode and VS C++ debuggers unable to visualize Rust HashMap. Since this bug is debugger specific, the proper solution should come from the WinDbg side.

[ChrisDenton]

Did this issue every get fixed on the WinDbg side?