Don't panic on broken pipes when built without termcolor #221
Description
Depending on if termcolor crate is used or not env_logger's behavior on closed stderr (or stdout) is different. When using termcolor and the output is closed the process just hangs. When not using termcolor a panic occurs because of broken pipe and process is terminated.
I'm not sure how this case should work. Hanging indefinitely is bad and might lead to hard to debug issues. But to panic without possibility to recover is also bad.
An example for reproducing and testing (tested on macOS 11.6):
Cargo.toml:
[package]
name = "envltest"
version = "0.1.0"
edition = "2021"
[features]
termcolor = [ "env_logger/termcolor" ]
[dependencies]
env_logger = { version = "0.9", default_features = false }
log = "0.4"main.rs:
fn main() {
env_logger::builder()
// This is to not hide error messages on stderr
.target(env_logger::Target::Stdout)
.init();
for i in 0.. {
log::info!("{}", i);
std::thread::sleep(std::time::Duration::from_secs(1));
}
}When env_logger is build with no default features (as seen in Cargo.toml) the process is terminated as soon as stdout is closed (head -n3 takes three lines and closes stdout):
% cargo build && RUST_LOG=info /tmp/rust/target/debug/envltest | head -n3
Finished dev [unoptimized + debuginfo] target(s) in 0.02s
[INFO envltest] 0
[INFO envltest] 1
[INFO envltest] 2
thread 'main' panicked at 'failed printing to stdout: Broken pipe (os error 32)', library/std/src/io/stdio.rs:1193:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtracehowever, when compiled with termcolor crate the process just hangs until the process is terminated manually:
% cargo build --features termcolor && RUST_LOG=info /tmp/rust/target/debug/envltest | head -n3
Finished dev [unoptimized + debuginfo] target(s) in 0.02s
[INFO envltest] 0
[INFO envltest] 1
[INFO envltest] 2
^CBacktrace of broken pipe:
thread 'main' panicked at 'failed printing to stdout: Broken pipe (os error 32)', library/std/src/io/stdio.rs:1193:9
stack backtrace:
0: rust_begin_unwind
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/std/src/panicking.rs:517:5
1: std::panicking::begin_panic_fmt
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/std/src/panicking.rs:460:5
2: std::io::stdio::print_to
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/std/src/io/stdio.rs:1193:9
3: std::io::stdio::_print
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/std/src/io/stdio.rs:1205:5
4: env_logger::fmt::writer::termcolor::imp::BufferWriter::print
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/fmt/writer/termcolor/shim_impl.rs:47:39
5: env_logger::fmt::writer::Writer::print
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/fmt/writer/mod.rs:120:9
6: env_logger::fmt::Formatter::print
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/fmt/mod.rs:115:9
7: <env_logger::Logger as log::Log>::log::{{closure}}::{{closure}}
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/lib.rs:928:67
8: core::result::Result<T,E>::and_then
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/core/src/result.rs:966:22
9: <env_logger::Logger as log::Log>::log::{{closure}}
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/lib.rs:928:21
10: <env_logger::Logger as log::Log>::log::{{closure}}
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/lib.rs:947:33
11: std::thread::local::LocalKey<T>::try_with
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/std/src/thread/local.rs:399:16
12: <env_logger::Logger as log::Log>::log
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/env_logger-0.9.0/src/lib.rs:934:27
13: log::__private_api_log
at /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/log-0.4.14/src/lib.rs:1460:5
14: envltest::main
at ./src/main.rs:7:9
15: core::ops::function::FnOnce::call_once
at /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/library/core/src/ops/function.rs:227:5