[lldb] Option<String> with empty string incorrectly displayed as None

[jennjwang]

Description

When debugging Rust code with LLDB, Option containing an empty string (Some(String::from(""))) is incorrectly displayed as None in the debugger. However, Option<&str> with an empty string displays correctly as Some("").

This appears to be a regression in the LLDB formatters (rustlib/etc/lldb_providers.py).

Environment

• OS: macOS (Apple Silicon / aarch64-apple-darwin)
• Rust: 1.83.0 stable (and nightly)
• LLDB: bundled with Xcode
• IDE: VSCode + CodeLLDB v1.12.0

Affected Versions

Rust Version	CodeLLDB Version	Status
~1.80	v1.10.0	✅ Works correctly
1.81+	v1.11.0+	❌ Bug present

Steps to Reproduce

fn main() {
// Case 1: String - BROKEN
let ss = String::from("");
let v = Some(ss);
let is_none = v.is_none();
println!("{v:?} {is_none}"); // Prints: Some("") false

  // Case 2: &str - WORKS
  let ss2 = "";
  let v2 = Some(ss2);
  println!("{v2:?}");  // Prints: Some("")

}

Set a breakpoint at println! and inspect variables in LLDB.

Expected Behavior

Variable	Expected Display
v (OptionString)	Some("")
is_none	false

Actual Behavior

Variable	Actual Display
v (OptionString)	None ❌
is_none	false ✅

The fact that is_none = false proves that v is actually Some, but the debugger displays it as None.

Screenshots

Analysis

The issue likely lies in rustlib/etc/lldb_providers.py, specifically in how ClangEncodedEnumProvider handles niche-optimized enums like Option. When the String is empty, the memory layout may be misinterpreted as None.

Related

• Similar issue was previously fixed in CodeLLDB: Unable to inspect for correct value in rust vadimcn/codelldb#726