std::arch::is_aarch64_feature_detected panics on aarch64 ilp32 targets

[h3fang]

I tried this code targeting aarch64-unknown-linux-gnu_ilp32:

fn main() {
    println!("Hello, world!");
}

I expected the code to run and print Hello, world!.

The release build did work as expected, but the debug build panicked immediately.

Meta

rustc --version --verbose:

rustc 1.91.0-nightly (a1208bf76 2025-09-03)
binary: rustc
commit-hash: a1208bf765ba783ee4ebdc4c29ab0a0c215806ef
commit-date: 2025-09-03
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0

Backtrace

thread '<unnamed>' (26966) panicked at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/bit.rs:7:5:
bit index out-of-bounds
stack backtrace:
   0:   0x67df18 - std::backtrace_rs::backtrace::libunwind::trace::ha888a12b7aef67b6
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:   0x67df18 - std::backtrace_rs::backtrace::trace_unsynchronized::hb1cf980d8ad8d153
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2:   0x5cc4ec - std::sys::backtrace::_print_fmt::h216f0cd897531371
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:66:9
   3:   0x5d92dc - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8cac44eeae6f1dcf
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:39:26
   4:   0x6dd174 - core::fmt::rt::Argument::fmt::hab3fc168f0d5532c
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:173:76
   5:   0x6e0d94 - core::fmt::write::hb93fdafb8e2f7f02
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:1468:25
   6:   0x623a34 - std::io::default_write_fmt::h8eed98e2a173ba5e
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:639:11
   7:   0x624d30 - std::io::Write::write_fmt::h374458ccfe0748f0
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:1954:13
   8:   0x5cccac - std::sys::backtrace::BacktraceLock::print::h36b039c3ce9060f6
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:42:9
   9:   0x5e57b0 - std::panicking::default_hook::{{closure}}::ha72b36dc3eae2870
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:301:27
  10:   0x5e566c - std::panicking::default_hook::h2fe0bb98267cb206
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:328:9
  11:   0x5e61f4 - std::panicking::panic_with_hook::h4a45c3c563138742
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:834:13
  12:   0x5e5d40 - std::panicking::panic_handler::{{closure}}::hd10b483ce921483f
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:700:13
  13:   0x5cd018 - std::sys::backtrace::__rust_end_short_backtrace::h90c201f540c43f11
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:174:18
  14:   0x5e3cd4 - __rustc[4dd267c369f14767]::rust_begin_unwind
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:698:5
  15:   0x6e2abc - core::panicking::panic_fmt::h3117ee1fcee79620
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:75:14
  16:   0x6bbd88 - std_detect::detect::bit::test::hcdd5f6d004b84a0e
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/bit.rs:7:5
  17:   0x6bc57c - <std_detect::detect::os::aarch64::AtHwcap as core::convert::From<std_detect::detect::os::auxvec::AuxVec>>::from::hd66e67cf609dafd0
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/os/linux/aarch64.rs:212:19
  18:   0x6bd74c - <T as core::convert::Into<U>>::into::h769583641c1250f0
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:784:9
  19:   0x6bace4 - std_detect::detect::os::aarch64::detect_features::h6bf17fd79d1a3c84
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/os/linux/aarch64.rs:26:35
  20:   0x6bbf9c - std_detect::detect::cache::detect_and_initialize::h7bc2971772ecb795
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:178:16
  21:   0x653820 - std_detect::detect::cache::test::{{closure}}::hb4db31dc3bb28ff9
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:202:53
  22:   0x5db664 - core::option::Option<T>::unwrap_or_else::h90d750cd835c5e5f
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1060:21
  23:   0x6537dc - std_detect::detect::cache::test::h11e18dbf97eed812
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:202:35
  24:   0x601620 - std_detect::detect::check_for::h05ca2a92f6939a0d
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/mod.rs:89:5
  25:   0x5b9d38 - std_detect::detect::arch::aarch64::__is_feature_detected::lse::h1ab2316e94fbafcb
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/macros.rs:198:21
  26:   0x5f61a0 - std::sys::configure_builtins::RUST_LSE_INIT::init_lse::h5120613a3cdc8e6a
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/configure_builtins.rs:15:12
  27: 0xf7b1dc34 - __libc_start_main
  28:   0x5b86b0 - _start
                       at /usr1/compiler_cpu/open_source/hcc_arm64le_build_src/linaro-glibc/csu/../sysdeps/aarch64/start.S:81:0
  29:        0x0 - <unknown>

thread '<unnamed>' (26966) panicked at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:225:5:
panic in a function that cannot unwind
stack backtrace:
   0:   0x67df18 - std::backtrace_rs::backtrace::libunwind::trace::ha888a12b7aef67b6
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:   0x67df18 - std::backtrace_rs::backtrace::trace_unsynchronized::hb1cf980d8ad8d153
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2:   0x5cc4ec - std::sys::backtrace::_print_fmt::h216f0cd897531371
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:66:9
   3:   0x5d92dc - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8cac44eeae6f1dcf
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:39:26
   4:   0x6dd174 - core::fmt::rt::Argument::fmt::hab3fc168f0d5532c
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:173:76
   5:   0x6e0d94 - core::fmt::write::hb93fdafb8e2f7f02
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:1468:25
   6:   0x623a34 - std::io::default_write_fmt::h8eed98e2a173ba5e
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:639:11
   7:   0x624d30 - std::io::Write::write_fmt::h374458ccfe0748f0
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:1954:13
   8:   0x5cccac - std::sys::backtrace::BacktraceLock::print::h36b039c3ce9060f6
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:42:9
   9:   0x5e57b0 - std::panicking::default_hook::{{closure}}::ha72b36dc3eae2870
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:301:27
  10:   0x5e566c - std::panicking::default_hook::h2fe0bb98267cb206
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:328:9
  11:   0x5e61f4 - std::panicking::panic_with_hook::h4a45c3c563138742
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:834:13
  12:   0x5e5d40 - std::panicking::panic_handler::{{closure}}::hd10b483ce921483f
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:700:13
  13:   0x5cd018 - std::sys::backtrace::__rust_end_short_backtrace::h90c201f540c43f11
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:174:18
  14:   0x5e3cd4 - __rustc[4dd267c369f14767]::rust_begin_unwind
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:698:5
  15:   0x6e267c - core::panicking::panic_nounwind_fmt::runtime::h02d65aeedacd27db
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:117:22
  16:   0x6e2620 - core::panicking::panic_nounwind_fmt::h9affb9da96f5b8e3
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/intrinsics/mod.rs:2380:9
  17:   0x6e2558 - core::panicking::panic_nounwind::h6e2452b4c310eef1
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:225:5
  18:   0x6e28b8 - core::panicking::panic_cannot_unwind::h5c5caf45a331068b
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:337:5
  19:   0x5f61ac - std::sys::configure_builtins::RUST_LSE_INIT::init_lse::h5120613a3cdc8e6a
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/configure_builtins.rs:7:5
  20: 0xf7b1dc34 - __libc_start_main
  21:   0x5b86b0 - _start
                       at /usr1/compiler_cpu/open_source/hcc_arm64le_build_src/linaro-glibc/csu/../sysdeps/aarch64/start.S:81:0
  22:        0x0 - <unknown>
thread caused non-unwinding panic. aborting.
Aborted

Analysis

From the backtrace we can see that

  26:   0x5f61a0 - std::sys::configure_builtins::RUST_LSE_INIT::init_lse::h5120613a3cdc8e6a
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/configure_builtins.rs:15:12

introduced in #144705 get called by the debug build, since the condition is satisfied

rust/library/std/src/sys/configure_builtins.rs

Lines 3 to 22 in 91edc3e

	#[cfg(all(target_arch = "aarch64", target_os = "linux", not(feature = "compiler-builtins-c")))]
	#[used]
	#[unsafe(link_section = ".init_array.90")]
	static RUST_LSE_INIT: extern "C" fn() = {
	extern "C" fn init_lse() {
	use crate::arch;
	// This is provided by compiler-builtins::aarch64_linux.
	unsafe extern "C" {
	fn __rust_enable_lse();
	}
	if arch::is_aarch64_feature_detected!("lse") {
	unsafe {
	__rust_enable_lse();
	}
	}
	}
	init_lse
	};

which called std::arch::is_aarch64_feature_detected!("lse"), and further up in the backtrace, we have

  16:   0x6bbd88 - std_detect::detect::bit::test::hcdd5f6d004b84a0e
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/bit.rs:7:5
  17:   0x6bc57c - <std_detect::detect::os::aarch64::AtHwcap as core::convert::From<std_detect::detect::os::auxvec::AuxVec>>::from::hd66e67cf609dafd0
                       at /home/hefang/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/os/linux/aarch64.rs:212:19

which calls line 212 bit::test(auxv.hwcap2, 34)

rust/library/std_detect/src/detect/os/linux/aarch64.rs

Lines 209 to 212 in 91edc3e

	wfxt: bit::test(auxv.hwcap2, 31),
	// ebf16: bit::test(auxv.hwcap2, 32),
	// sveebf16: bit::test(auxv.hwcap2, 33),
	cssc: bit::test(auxv.hwcap2, 34),

and bit::test calls

rust/library/std_detect/src/detect/bit.rs

Lines 6 to 9 in 91edc3e

	pub(crate) fn test(x: usize, bit: u32) -> bool {
	debug_assert!(bit < usize::BITS, "bit index out-of-bounds");
	x & (1 << bit) != 0
	}

Since usize in gnu_ilp32 only have 32 bits, 34 > usize::BITS it panics.

So the root cause is AuxVec uses usize for hwcap2 even for ilp32 target.

rust/library/std_detect/src/detect/os/linux/auxvec.rs

Lines 24 to 34 in 91edc3e

	pub(crate) struct AuxVec {
	pub hwcap: usize,
	#[cfg(any(
	target_arch = "aarch64",
	target_arch = "arm",
	target_arch = "powerpc",
	target_arch = "powerpc64",
	target_arch = "s390x",
	))]
	pub hwcap2: usize,
	}

Given this conclusion, rustc previous to #144705 should still panics if std::arch::is_aarch64_feature_detected is called explicitly, which can be verified with this code

fn main() {
    println!("{:?}", std::arch::is_aarch64_feature_detected!("lse"));
}

and rustc

rustc 1.91.0-nightly (7d82b83ed 2025-08-06)
binary: rustc
commit-hash: 7d82b83ed57d188ab3f2441a765a6419685a88a3
commit-date: 2025-08-06
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0

Backtrace

thread 'main' panicked at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/bit.rs:7:5:
bit index out-of-bounds
stack backtrace:
   0:   0x934cbc - std::backtrace_rs::backtrace::libunwind::trace::hb7d4b84d8c2e02ab
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:   0x934cbc - std::backtrace_rs::backtrace::trace_unsynchronized::h3ada69107ee9388c
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2:   0x9a8244 - std::sys::backtrace::_print_fmt::hfca14e91eae21a99
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:66:9
   3:   0x9a8070 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hb7a51c92e7c0fb30
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:39:26
   4:   0xa11590 - core::fmt::rt::Argument::fmt::h3ec082dd9d763eb9
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:173:76
   5:   0xa0cd4c - core::fmt::write::h823ded8ad22a509c
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:1468:25
   6:   0x9003d8 - std::io::default_write_fmt::ha6bf82aaf9b08baf
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:639:11
   7:   0x91579c - std::io::Write::write_fmt::h64774c751368c298
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:1954:13
   8:   0x9a8030 - std::sys::backtrace::BacktraceLock::print::hc57934af0b2205ed
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:42:9
   9:   0x927db4 - std::panicking::default_hook::{{closure}}::h3a5ba982b4691b97
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:300:27
  10:   0x927c70 - std::panicking::default_hook::h78d4d8f20a10bf31
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:327:9
  11:   0x9293c0 - std::panicking::panic_with_hook::h0b73ec61f68d09d6
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:833:13
  12:   0x928f0c - std::panicking::begin_panic_handler::{{closure}}::h5db60d7bd710d3b9
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:699:13
  13:   0x9a8998 - std::sys::backtrace::__rust_end_short_backtrace::h08053735ac5c1576
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:174:18
  14:   0x928b00 - __rustc[a5fd53d223c672bb]::rust_begin_unwind
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:697:5
  15:   0xa0f6e4 - core::panicking::panic_fmt::ha4dd93fdae3bbe31
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panicking.rs:75:14
  16:   0x9df2f8 - std_detect::detect::bit::test::hb24c4124e63ba631
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/bit.rs:7:5
  17:   0x9e0440 - <std_detect::detect::os::aarch64::AtHwcap as core::convert::From<std_detect::detect::os::auxvec::AuxVec>>::from::h7f9a03bdeb2e601f
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/os/linux/aarch64.rs:212:19
  18:   0x9de8e0 - <T as core::convert::Into<U>>::into::h495a73b7b6dffc5e
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:784:9
  19:   0x9dff90 - std_detect::detect::os::aarch64::detect_features::h666a21be35557fef
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/os/linux/aarch64.rs:26:35
  20:   0x9df5f8 - std_detect::detect::cache::detect_and_initialize::h8e96e7b858cc9241
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:176:16
  21:   0x8dd9bc - std_detect::detect::cache::test::{{closure}}::h50539c0a8c463579
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:200:53
  22:   0x8dd8f4 - core::option::Option<T>::unwrap_or_else::h4417da605506525b
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1060:21
  23:   0x8ddc78 - std_detect::detect::cache::test::hcb75959fd2b3e404
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/cache.rs:200:35
  24:   0x8dd87c - std_detect::detect::check_for::h5bd1fcabd31fbcac
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/mod.rs:84:5
  25:   0x8dd9f0 - std_detect::detect::arch::aarch64::__is_feature_detected::lse::h30d01b201f55a5db
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std_detect/src/detect/macros.rs:198:21
  26:   0x8dda28 - arm::main::he934d38792ac3eed
                       at /home/hefang/projects/arm/src/main.rs:2:22
  27:   0x8dde4c - core::ops::function::FnOnce::call_once::h32ed432bdfa81d8d
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:253:5
  28:   0x8ddda8 - std::sys::backtrace::__rust_begin_short_backtrace::h5a662b4ccf97c691
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:158:18
  29:   0x8dd988 - std::rt::lang_start::{{closure}}::ha21ce39d2d73b343
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:206:18
  30:   0x941b3c - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::hc2e5e48f52d4dba2
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:290:21
  31:   0x928594 - std::panicking::catch_unwind::do_call::h7fd9226072622079
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:589:40
  32:   0x929504 - __rust_try
  33:   0x928310 - std::panicking::catch_unwind::ha2f1ff83857a5486
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:19
  34:   0x8f9078 - std::panic::catch_unwind::hb2e4614027fccc1b
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  35:   0x8df748 - std::rt::lang_start_internal::{{closure}}::hd67c6cfe67d1165a
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:175:24
  36:   0x9284f0 - std::panicking::catch_unwind::do_call::h0288665ffae0424f
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:589:40
  37:   0x929504 - __rust_try
  38:   0x9281d8 - std::panicking::catch_unwind::h11b8a23d6a858a22
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:19
  39:   0x8f9034 - std::panic::catch_unwind::h6990698e0251b327
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  40:   0x8df6e4 - std::rt::lang_start_internal::hf7b35c32c2cfdb89
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:171:5
  41:   0x8dd95c - std::rt::lang_start::ha497327c85745e43
                       at /home/hefang/.rustup/toolchains/nightly-2025-08-07-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:205:5
  42:   0x8ddaa0 - main
  43: 0xf78fea4c - <unknown>
  44: 0xf78feb24 - __libc_start_main
  45:   0x8dd6f0 - _start
                       at /usr1/compiler_cpu/open_source/hcc_arm64le_build_src/linaro-glibc/csu/../sysdeps/aarch64/start.S:81:0
  46:        0x0 - <unknown>

[folkertdev]

For ease of testing/reproduction, how do you actually run these binaries (I'm assuming/hoping there is some qemu config)?

[h3fang]

Unfortunately, the build process requires linking with gnu_ilp32 libc, and the binary has to run on a gnu_ilp32 linux. Both can not be shared publicly.

qemu rejected the patches for aarch64 ilp32 support https://lists.gnu.org/archive/html/qemu-arm/2025-02/msg01252.html , and the patches for linux kernel aarch64 ilp32 support is also discontinued. https://wiki.linaro.org/

The only thing I can find publicly is this docker image https://hub.docker.com/r/leapproject/leap-aarch64_ilp32-toolchain . Or we have to build every thing with aarch64 ilp32 support.

[folkertdev]

In that case, given that you've already done the digging to find the problem, are you up for just fixing this yourself and submitting a PR?

The value is (probably) truncated here

rust/library/std_detect/src/detect/os/linux/auxvec.rs

Line 155 in 91edc3e

Ok(unsafe { ffi_getauxval(key as libc::c_ulong) as usize })

So presumably the AuxVec type needs to store std::ffi::c_ulong instead of usize.

[h3fang]

Sure, I am willing to propose the PR, and feel excited to contribute code to Rust for the first time.