Code
Project structure:
project/
├── Cargo.toml
├── build.rs
└── src/
├── foo.c <── empty
└── lib.rs <── empty
Cargo.toml:
[package]
name = "project"
edition = "2024"
build = "build.rs"
[build-dependencies]
ar = "0.9.0"
cc = "1.0"
build.rs:
use ar::Builder;
use std::{env, fs::{self, File}, path::Path, process::Command};
fn main() {
let build_path = env::var("OUT_DIR").expect("OUT_DIR not set by Cargo");
let lib_path = Path::new(&build_path).join("lib");
let l_path = lib_path.join("libl.a");
if !lib_path.exists() {
fs::create_dir_all(&lib_path).expect("Failed to create 'lib' directory");
}
let mut builder = Builder::new(File::create(&l_path).unwrap());
let max_name_length = 15; // set this to 14 to hide the bug
cc::Build::new()
.file("src/foo.c")
.compile_intermediates()
.iter()
.map(|object| { // only needed to trim the object filename for hiding the bug
let object_path = Path::new(&object);
let file_name = object_path.file_stem().expect("could not take file stem");
let base_name = file_name.display().to_string();
let trimmed_name = base_name.get(base_name.len().saturating_sub(max_name_length)..).unwrap_or(&base_name);
let new_path = object_path.parent().expect("could not take parent").join(format!("{}.o", trimmed_name));
fs::rename(object_path, &new_path).expect("Failed to rename object file");
new_path
})
.for_each(|object| builder.append_path(object).expect("could not add object to archive"));
Command::new("ranlib")
.arg(&l_path)
.status()
.expect("Failed to run ranlib");
println!("cargo:rustc-link-search={}", lib_path.display());
println!("cargo:rustc-link-lib=static={}", "l");
}Meta
rustc --version --verbose:
rustc 1.90.0 (1159e78c4 2025-09-14)
binary: rustc
commit-hash: 1159e78c4747b02ef996e55082b704c09b970588
commit-date: 2025-09-14
host: x86_64-unknown-linux-gnu
release: 1.90.0
LLVM version: 20.1.8
Error output
error: the compiler unexpectedly panicked. this is a bug.
Backtrace
thread 'rustc' panicked at compiler/rustc_codegen_ssa/src/back/archive.rs:481:29:
range end index 1576 out of range for slice of length 1556
stack backtrace:
0: 0x7f7c4ea00f83 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hdcfcb6d4c8489523
1: 0x7f7c4f202d77 - core::fmt::write::h8a494366950f23bb
2: 0x7f7c505d14d1 - std::io::Write::write_fmt::h6556609fca33d0b1
3: 0x7f7c4ea00de2 - std::sys::backtrace::BacktraceLock::print::hb2a626a81e06b2dc
4: 0x7f7c4ea04887 - std::panicking::default_hook::{{closure}}::h4f78485264f12d10
5: 0x7f7c4ea043eb - std::panicking::default_hook::h2c66fc99e962531d
6: 0x7f7c4da627e3 - std[9479b33d5e275715]::panicking::update_hook::<alloc[252dd2b3abdfe4a]::boxed::Box<rustc_driver_impl[773a1ede480c2143]::install_ice_hook::{closure#1}>>::{closure#0}
7: 0x7f7c4ea050ce - std::panicking::rust_panic_with_hook::h33ac55f64bbd807d
8: 0x7f7c4ea04dca - std::panicking::begin_panic_handler::{{closure}}::h30e7cb89678a57fe
9: 0x7f7c4ea01459 - std::sys::backtrace::__rust_end_short_backtrace::hed60f27456c16ced
10: 0x7f7c4ea04aad - __rustc[de2ca18b4c54d5b8]::rust_begin_unwind
11: 0x7f7c4b0d01a0 - core::panicking::panic_fmt::h62f63d096dd276af
12: 0x7f7c4d428157 - core::slice::index::slice_end_index_len_fail::do_panic::runtime::he43cf2c157f763ee
13: 0x7f7c4c9bc5aa - core::slice::index::slice_end_index_len_fail::hb04774ae50b54dc9
14: 0x7f7c503266a0 - <rustc_codegen_ssa[8cc6941b80b7847a]::back::archive::ArArchiveBuilder>::build_inner
15: 0x7f7c50323c2c - <rustc_codegen_ssa[8cc6941b80b7847a]::back::archive::ArArchiveBuilder as rustc_codegen_ssa[8cc6941b80b7847a]::back::archive::ArchiveBuilder>::build
16: 0x7f7c50329236 - rustc_codegen_ssa[8cc6941b80b7847a]::back::link::link_binary
17: 0x7f7c504c7628 - <rustc_interface[c9c4c8df4db17049]::queries::Linker>::link
18: 0x7f7c504c131b - rustc_interface[c9c4c8df4db17049]::interface::run_compiler::<(), rustc_driver_impl[773a1ede480c2143]::run_compiler::{closure#0}>::{closure#1}
19: 0x7f7c503751c1 - std[9479b33d5e275715]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[c9c4c8df4db17049]::util::run_in_thread_with_globals<rustc_interface[c9c4c8df4db17049]::util::run_in_thread_pool_with_globals<rustc_interface[c9c4c8df4db17049]::interface::run_compiler<(), rustc_driver_impl[773a1ede480c2143]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
20: 0x7f7c50374ea2 - <<std[9479b33d5e275715]::thread::Builder>::spawn_unchecked_<rustc_interface[c9c4c8df4db17049]::util::run_in_thread_with_globals<rustc_interface[c9c4c8df4db17049]::util::run_in_thread_pool_with_globals<rustc_interface[c9c4c8df4db17049]::interface::run_compiler<(), rustc_driver_impl[773a1ede480c2143]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[42326c15e70145c1]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
21: 0x7f7c5037a7c5 - std::sys::pal::unix::thread::Thread::new::thread_start::hb6e99e73da4d28f8
22: 0x7f7c49c6bac3 - start_thread
at ./nptl/pthread_create.c:442:8
23: 0x7f7c49cfd8c0 - __GI___clone3
at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81:0
24: 0x0 - <unknown>
build.rs compiles foo.c into a static library by following the following steps:
- generate the object
.o file (compile_intermediates())
- pack it into
.a archive (ar::Builder)
- add index with
ranlib
An additional step for trimming the object filename was added to show that if the full simple name is less than 15, the panic does not manifest (set max_name_length).
Code
Project structure:
Cargo.toml:build.rs:Meta
rustc --version --verbose:Error output
Backtrace
build.rscompilesfoo.cinto a static library by following the following steps:.ofile (compile_intermediates()).aarchive (ar::Builder)ranlibAn additional step for trimming the object filename was added to show that if the full simple name is less than 15, the panic does not manifest (set
max_name_length).