% cargo +nightly-2020-04-07-x86_64-apple-darwin miri
    Checking fb-repro v0.1.0 (/private/tmp/fb-repro)
error: Undefined Behavior: accessing memory with alignment 1, but alignment 4 is required
   --> /Users/shep/.cargo/registry/src/github.com-1ecc6299db9ec823/flatbuffers-0.6.1/src/endian_scalar.rs:157:9
    |
157 |         *mut_ptr = val;
    |         ^^^^^^^^^^^^^^ accessing memory with alignment 1, but alignment 4 is required
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: inside `flatbuffers::endian_scalar::emplace_scalar::<u32>` at /Users/shep/.cargo/registry/src/github.com-1ecc6299db9ec823/flatbuffers-0.6.1/src/endian_scalar.rs:157:9
    = note: inside `<u32 as flatbuffers::push::Push>::push` at /Users/shep/.cargo/registry/src/github.com-1ecc6299db9ec823/flatbuffers-0.6.1/src/push.rs:64:17
    = note: inside `flatbuffers::builder::FlatBufferBuilder::push::<u32>` at /Users/shep/.cargo/registry/src/github.com-1ecc6299db9ec823/flatbuffers-0.6.1/src/builder.rs:140:13
    = note: inside `flatbuffers::builder::FlatBufferBuilder::create_vector_direct::<i32>` at /Users/shep/.cargo/registry/src/github.com-1ecc6299db9ec823/flatbuffers-0.6.1/src/builder.rs:282:9
note: inside `main` at src/main.rs:3:5
   --> src/main.rs:3:5
    |
3   |     builder.create_vector_direct(&[1,2,3]);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: inside closure at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:67:34
    = note: inside closure at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:52:73
    = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<[closure@DefId(1:6093 ~ std[5a71]::rt[0]::lang_start_internal[0]::{{closure}}[0]::{{closure}}[0]) 0:&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/sys_common/backtrace.rs:130:5
    = note: inside closure at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:52:13
    = note: inside `std::panicking::r#try::do_call::<[closure@DefId(1:6092 ~ std[5a71]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panicking.rs:331:40
    = note: inside `std::panicking::r#try::<i32, [closure@DefId(1:6092 ~ std[5a71]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe]>` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panicking.rs:274:15
    = note: inside `std::panic::catch_unwind::<[closure@DefId(1:6092 ~ std[5a71]::rt[0]::lang_start_internal[0]::{{closure}}[0]) 0:&&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe], i32>` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/panic.rs:394:14
    = note: inside `std::rt::lang_start_internal` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:51:25
    = note: inside `std::rt::lang_start::<()>` at /Users/shep/.rustup/toolchains/nightly-2020-04-07-x86_64-apple-darwin/lib/rustlib/src/rust/src/libstd/rt.rs:67:5

% rustc +nightly-2020-04-07-x86_64-apple-darwin --version --verbose
rustc 1.44.0-nightly (6dee5f112 2020-04-06)
binary: rustc
commit-hash: 6dee5f1126dfd5c9314ee5ae9d9eb010e35ef257
commit-date: 2020-04-06
host: x86_64-apple-darwin
release: 1.44.0-nightly
LLVM version: 9.0