ICE on Linux kernel 2.6

[cjgillot]

I tried to compile rustc on an elderly Linux box.
cargo panicked.

I traced the cause to https://github.com/rust-lang/cargo/blob/master/src/cargo/util/cpu.rs#L66
The unwrap panics because the /proc/stat file on this version only has 9 columns.

Backtrace:

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:378:21                                                                                     [62/528]
stack backtrace:
   0:     0x55d3d4e19914 - backtrace::backtrace::libunwind::trace::h7ad6a8b922fcbc6b
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/libunwind.rs:88
   1:     0x55d3d4e19914 - backtrace::backtrace::trace_unsynchronized::hbac2e1529d61bd77
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/mod.rs:66
   2:     0x55d3d4e19914 - std::sys_common::backtrace::_print_fmt::hbe7c998fd23d81c1
                               at src/libstd/sys_common/backtrace.rs:76
   3:     0x55d3d4e19914 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hd16e96c1802eeddf
                               at src/libstd/sys_common/backtrace.rs:60
   4:     0x55d3d4e44efc - core::fmt::write::h6eabb3ca7a98a71e
                               at src/libcore/fmt/mod.rs:1030
   5:     0x55d3d4e12317 - std::io::Write::write_fmt::h9ff2cb44f8ed5906
                               at src/libstd/io/mod.rs:1412
   6:     0x55d3d4e1d675 - std::sys_common::backtrace::_print::h156faaaa311a1c35
                               at src/libstd/sys_common/backtrace.rs:64
   7:     0x55d3d4e1d675 - std::sys_common::backtrace::print::hd8f44adca3b9c7af
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x55d3d4e1d675 - std::panicking::default_hook::{{closure}}::h7d7cdcb2c7cdbed8
                               at src/libstd/panicking.rs:196
   9:     0x55d3d4e1d366 - std::panicking::default_hook::hb4a9065c39b6e99a
                               at src/libstd/panicking.rs:210
  10:     0x55d3d4e1dd75 - std::panicking::rust_panic_with_hook::haa206b44ed70b8bb
                               at src/libstd/panicking.rs:473
  11:     0x55d3d4e1d912 - std::panicking::continue_panic_fmt::h4f54b156fa6d4e21
                               at src/libstd/panicking.rs:380
  12:     0x55d3d4e1d806 - rust_begin_unwind
                               at src/libstd/panicking.rs:307
  13:     0x55d3d4e4151a - core::panicking::panic_fmt::h6f2ecda11bddbc92
                               at src/libcore/panicking.rs:85
  14:     0x55d3d4e41459 - core::panicking::panic::h0aaff6652230cf96
                               at src/libcore/panicking.rs:49
  15:     0x55d3d499e3c4 - cargo::util::cpu::imp::current::h9802aac11537b886
  16:     0x55d3d48ac488 - cargo::core::compiler::job_queue::JobQueue::new::h2597d495a607c29f
  17:     0x55d3d46608b2 - cargo::core::compiler::context::Context::compile::ha8ff39d166541d11
  18:     0x55d3d4674d9f - cargo::ops::cargo_compile::compile_ws::h6cf0023976f380bb
  19:     0x55d3d466fbe7 - cargo::ops::cargo_compile::compile::he794ebb8a966f792
  20:     0x55d3d45b9276 - cargo::commands::build::exec::h64fcef8244062342
  21:     0x55d3d456fd81 - cargo::cli::main::h1d2b305aba351553
  22:     0x55d3d45bcc11 - cargo::main::hd0239c9be1c49e24
  23:     0x55d3d45a72d3 - std::rt::lang_start::{{closure}}::h7c37522af7759eb6
  24:     0x55d3d4e1d7a3 - std::rt::lang_start_internal::{{closure}}::hb544445db001314b
                               at src/libstd/rt.rs:49
  25:     0x55d3d4e1d7a3 - std::panicking::try::do_call::hb9787e39316b7f40
                               at src/libstd/panicking.rs:292
  26:     0x55d3d4e28daa - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:80

Possible Solution(s)

Remove that unwrap by a unwrap_or_else("0").

Output of cargo version:

cargo 1.39.0-beta (b6c6f68 2019-09-19)

[ehuss]

cargo 1.39.0-beta (b6c6f68 2019-09-19)

FWIW, this version is very old, and this issue was fixed in #7430. Can you try a newer version of Rust?

[cjgillot]

This is the version which is downloaded by the rustc bootstrap process. I managed to get it working by manually downloading the previous (2019-08-23) version. I will try a newer version when convenient.

Otherwise, thank you for the fix :)