cargo-careful: empty libtest harness under cargo-careful fails valgrind

Steps to reproduce:

mkdir /tmp/memory-error && cd /tmp/memory-error
cargo init --lib
cargo +nightly careful test --no-run
valgrind --track-origins=yes target/debug/deps/memory_error-394e695bdd4a1e0f

Valgrind output:

==741342== Memcheck, a memory error detector
==741342== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==741342== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==741342== Command: target/debug/deps/memory_error-394e695bdd4a1e0f
==741342== 
==741342== Conditional jump or move depends on uninitialised value(s)
==741342==    at 0x16673A: runtime<u8> (raw.rs:93)
==741342==    by 0x16673A: from_raw_parts<u8> (intrinsics.rs:2220)
==741342==    by 0x16673A: deref<u8, alloc::alloc::Global> (mod.rs:2533)
==741342==    by 0x16673A: index (string.rs:2185)
==741342==    by 0x16673A: eq (string.rs:2185)
==741342==    by 0x16673A: eq (lib.rs:626)
==741342==    by 0x16673A: eq<getopts::Name, getopts::Name> (lib.rs:933)
==741342==    by 0x16673A: {closure#0} (lib.rs:933)
==741342==    by 0x16673A: position<getopts::Opt, getopts::find_opt::{closure_env#0}> (macros.rs:295)
==741342==    by 0x16673A: getopts::find_opt (lib.rs:933)
==741342==    by 0x166084: getopts::Matches::opt_vals (lib.rs:797)
==741342==    by 0x16634A: getopts::Matches::opt_present (lib.rs:813)
==741342==    by 0x13C548: test::cli::parse_opts (cli.rs:207)
==741342==    by 0x15A0FC: test::test_main (lib.rs:95)
==741342==    by 0x15B0D1: test::test_main_static (lib.rs:131)
==741342==    by 0x123112: memory_error::main (lib.rs:1)
==741342==    by 0x12307A: core::ops::function::FnOnce::call_once (function.rs:251)
==741342==    by 0x12315D: std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:122)
==741342==    by 0x122CE0: std::rt::lang_start::{{closure}} (rt.rs:166)
==741342==    by 0x18AA53: call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (function.rs:286)
==741342==    by 0x18AA53: do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panicking.rs:464)
==741342==    by 0x18AA53: try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panic.rs:137)
==741342==    by 0x18AA53: {closure#2} (rt.rs:148)
==741342==    by 0x18AA53: do_call<std::rt::lang_start_internal::{closure_env#2}, isize> (panicking.rs:464)
==741342==    by 0x18AA53: try<isize, std::rt::lang_start_internal::{closure_env#2}> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> (panic.rs:137)
==741342==    by 0x18AA53: std::rt::lang_start_internal (rt.rs:148)
==741342==    by 0x122CB9: std::rt::lang_start (rt.rs:165)
==741342==  Uninitialised value was created by a stack allocation
==741342==    at 0x165FE7: getopts::Matches::opt_vals (lib.rs:796)
==741342== 
==741342== Conditional jump or move depends on uninitialised value(s)
==741342==    at 0x16680E: runtime<u8> (raw.rs:93)
==741342==    by 0x16680E: from_raw_parts<u8> (intrinsics.rs:2220)
==741342==    by 0x16680E: deref<u8, alloc::alloc::Global> (mod.rs:2533)
==741342==    by 0x16680E: index (string.rs:2185)
==741342==    by 0x16680E: eq (string.rs:2185)
==741342==    by 0x16680E: eq (lib.rs:626)
==741342==    by 0x16680E: eq<getopts::Name, getopts::Name> (lib.rs:940)
==741342==    by 0x16680E: {closure#1} (lib.rs:940)
==741342==    by 0x16680E: any<getopts::Opt, getopts::find_opt::{closure_env#1}> (macros.rs:242)
==741342==    by 0x16680E: getopts::find_opt (lib.rs:940)
==741342==    by 0x166084: getopts::Matches::opt_vals (lib.rs:797)
==741342==    by 0x16634A: getopts::Matches::opt_present (lib.rs:813)
==741342==    by 0x13C548: test::cli::parse_opts (cli.rs:207)
==741342==    by 0x15A0FC: test::test_main (lib.rs:95)
==741342==    by 0x15B0D1: test::test_main_static (lib.rs:131)
==741342==    by 0x123112: memory_error::main (lib.rs:1)
==741342==    by 0x12307A: core::ops::function::FnOnce::call_once (function.rs:251)
==741342==    by 0x12315D: std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:122)
==741342==    by 0x122CE0: std::rt::lang_start::{{closure}} (rt.rs:166)
==741342==    by 0x18AA53: call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (function.rs:286)
==741342==    by 0x18AA53: do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panicking.rs:464)
==741342==    by 0x18AA53: try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panic.rs:137)
==741342==    by 0x18AA53: {closure#2} (rt.rs:148)
==741342==    by 0x18AA53: do_call<std::rt::lang_start_internal::{closure_env#2}, isize> (panicking.rs:464)
==741342==    by 0x18AA53: try<isize, std::rt::lang_start_internal::{closure_env#2}> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> (panic.rs:137)
==741342==    by 0x18AA53: std::rt::lang_start_internal (rt.rs:148)
==741342==    by 0x122CB9: std::rt::lang_start (rt.rs:165)
==741342==  Uninitialised value was created by a stack allocation
==741342==    at 0x165FE7: getopts::Matches::opt_vals (lib.rs:796)
==741342== 
==741342== Conditional jump or move depends on uninitialised value(s)
==741342==    at 0x16673A: runtime<u8> (raw.rs:93)
==741342==    by 0x16673A: from_raw_parts<u8> (intrinsics.rs:2220)
==741342==    by 0x16673A: deref<u8, alloc::alloc::Global> (mod.rs:2533)
==741342==    by 0x16673A: index (string.rs:2185)
==741342==    by 0x16673A: eq (string.rs:2185)
==741342==    by 0x16673A: eq (lib.rs:626)
==741342==    by 0x16673A: eq<getopts::Name, getopts::Name> (lib.rs:933)
==741342==    by 0x16673A: {closure#0} (lib.rs:933)
==741342==    by 0x16673A: position<getopts::Opt, getopts::find_opt::{closure_env#0}> (macros.rs:295)
==741342==    by 0x16673A: getopts::find_opt (lib.rs:933)
==741342==    by 0x166084: getopts::Matches::opt_vals (lib.rs:797)
==741342==    by 0x166643: getopts::Matches::opt_str (lib.rs:804)
==741342==    by 0x13C764: get_allow_unstable (cli.rs:471)
==741342==    by 0x13C764: parse_opts_impl (cli.rs:252)
==741342==    by 0x13C764: test::cli::parse_opts (cli.rs:214)
==741342==    by 0x15A0FC: test::test_main (lib.rs:95)
==741342==    by 0x15B0D1: test::test_main_static (lib.rs:131)
==741342==    by 0x123112: memory_error::main (lib.rs:1)
==741342==    by 0x12307A: core::ops::function::FnOnce::call_once (function.rs:251)
==741342==    by 0x12315D: std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:122)
==741342==    by 0x122CE0: std::rt::lang_start::{{closure}} (rt.rs:166)
==741342==    by 0x18AA53: call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (function.rs:286)
==741342==    by 0x18AA53: do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panicking.rs:464)
==741342==    by 0x18AA53: try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panic.rs:137)
==741342==    by 0x18AA53: {closure#2} (rt.rs:148)
==741342==    by 0x18AA53: do_call<std::rt::lang_start_internal::{closure_env#2}, isize> (panicking.rs:464)
==741342==    by 0x18AA53: try<isize, std::rt::lang_start_internal::{closure_env#2}> (panicking.rs:428)
==741342==    by 0x18AA53: catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> (panic.rs:137)
==741342==    by 0x18AA53: std::rt::lang_start_internal (rt.rs:148)
==741342==    by 0x122CB9: std::rt::lang_start (rt.rs:165)
==741342==  Uninitialised value was created by a stack allocation
==741342==    at 0x165FE7: getopts::Matches::opt_vals (lib.rs:796)
==741342== 

running 1 test
test tests::it_works ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.12s

==741342== 
==741342== HEAP SUMMARY:
==741342==     in use at exit: 0 bytes in 0 blocks
==741342==   total heap usage: 479 allocs, 479 frees, 53,506 bytes allocated
==741342== 
==741342== All heap blocks were freed -- no leaks are possible
==741342== 
==741342== For lists of detected and suppressed errors, rerun with: -s
==741342== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

I’ve tried to debug this with gdb and adding prints, but it disappears if you look at it too closely so gave up after a bit of trying