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UEFI: fmt::Debug for TcpStream/TcpListener is unimplemented!() and panics

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
rust
Domain
networking, operating-systems

Research direction

Start by reading the fmt::Debug implementations in library/std/src/sys/net/connection/uefi/mod.rs at lines 165–170 and 233–238, then check nearby platform implementations for the expected formatting style. Implement non-panicking debug output for TcpStream and TcpListener; done when formatting either type with {:?} no longer panics on UEFI.

Written by the indexing model from the issue text.

Description

C-bug needs-triage O-UEFI T-libs

On UEFI, the fmt::Debug implementations for TcpStream and TcpListener call
unimplemented!(), so any debug-print or log of these types panics the process
from safe code — including {:?}, .unwrap_err() on a Debug-bound error, or
any logging layer that formats them.

I tried this code:

use std::net::TcpListener;

let listener = TcpListener::bind("0.0.0.0:8080").unwrap();
println!("{listener:?}"); // panics: not yet implemented

I expected to see this happen: a Debug rendering (even a minimal
non-exhaustive one), as on all other platforms.

Instead, this happened: the impl is a stub
(library/std/src/sys/net/connection/uefi/mod.rs:165-170, and 233-238 for TcpListener):

impl fmt::Debug for TcpStream {
    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // FIXME(implement this)
        unimplemented!()
    }
}

Any debug-formatting of these types panics — a crash from safe code on a shipped
platform. The same applies to TcpListener.

Meta

Found by static analysis of main @ dc44e7f. Related: #100499.

rustc --version --verbose:

rustc 1.101.0-dev
binary: rustc
commit-hash: dc44e7f2c436b6041742e138b9c2176f093196d5
commit-date: 2026-10-24
host: x86_64-unknown-linux-gnu
release: 1.101.0-dev
Backtrace 

thread 'main' panicked at 'not yet implemented', library/std/src/sys/net/connection/uefi/mod.rs:167
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: <std::sys::net::connection::uefi::TcpStream as core::fmt::Debug>::fmt
   3: core::fmt::write
   4: std::io::stdio::_print
(representative; captured on a UEFI target)

@rustbot label +C-bug +T-libs +O-uefi

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