Embedded projects using `synopsys-usb-otg` are hanging in Beta/Nightly

[antonok-edm]

Code

I tried this code:

Cargo.toml

[dependencies]
stm32f4xx-hal = { version = "0.13", features = ["rt", "stm32f401", "usb_fs"] }
embedded-hal = "^ 0.2.6"
cortex-m = { version = "^ 0.7" }
cortex-m-rt = { version = "^ 0.7", features = ["device"] }
usb-device = "^ 0.2"

toolchain: thumbv7em-none-eabihf

main.rs

#![no_main]
#![no_std]
 
use stm32f4xx_hal::{
    otg_fs::{ USB as Peripheral, UsbBus },
    pac::Peripherals,
    prelude::*,
};
 
use usb_device::{
    bus::UsbBusAllocator,
    prelude::*,
};
 
#[entry]
fn main() -> ! {
    const SYS_CLOCK_MHZ: u32 = 84;
 
    const VID: u16 = 0x1337;
    const PID: u16 = 0x1337;
    const MANUFACTURER_NAME: &str = "test";
    const PRODUCT_NAME: &str = "test";
 
    static mut EP_MEMORY: [u32; 1024] = [0; 1024];
 
    let device = Peripherals::take().unwrap();
    let rcc = device.RCC.constrain();
 
    let clocks = rcc.cfgr
        .use_hse(25.MHz())
        .sysclk(SYS_CLOCK_MHZ.MHz())
        .require_pll48clk()
        .freeze();
    assert!(clocks.is_pll48clk_valid());
 
    let gpioa = device.GPIOA.split();
 
    let usb = stm32f4xx_hal::otg_fs::USB {
        usb_global: device.OTG_FS_GLOBAL,
        usb_device: device.OTG_FS_DEVICE,
        usb_pwrclk: device.OTG_FS_PWRCLK,
        pin_dm: gpioa.pa11.into_alternate(),
        pin_dp: gpioa.pa12.into_alternate(),
        hclk: clocks.hclk(),
    };
 
    let usb_allocator: UsbBusAllocator<UsbBus<Peripheral>>;
 
    usb_allocator = UsbBus::new(usb, unsafe { &mut EP_MEMORY });
 
    // Any code following this assignment never runs on Beta or Nightly
    let usb_bus = UsbDeviceBuilder::new(&usb_allocator, UsbVidPid(VID, PID))
        .manufacturer(MANUFACTURER_NAME)
        .product(PRODUCT_NAME)
        .device_class(0x00)
        .build();
 
    // activate a peripheral of your choice here to demonstrate
}

I expected to see this happen: the peripheral activation at the end should occur

Instead, this happened: the program hangs indefinitely

Version it worked on

It most recently worked on: Rust 1.66.1

Version with regression

rustc --version --verbose:

rustc 1.67.0-beta.7 (275123cf6 2023-01-11)
binary: rustc
commit-hash: 275123cf608aad2c3b48c7a53b019430244e4574
commit-date: 2023-01-11
host: x86_64-unknown-linux-gnu
release: 1.67.0-beta.7
LLVM version: 15.0.6

More details

See also @hacknus's provided examples, investigation, and debugger output at stm32-rs/synopsys-usb-otg#33. I don't have the ability to run a debugger on my hardware, unfortunately.

cc @adamgreig who has also reproduced the issue.

Some bisecting

nightly-2022-11-09 does not have the issue
nightly-2022-11-19 does not have the issue
nightly-2022-11-21 does not have the issue
nightly-2022-11-22 does not have the issue
nightly-2022-11-24 does have the issue

[adamgreig]

I'm pretty sure this is #102750 and a bug in https://github.com/stm32-rs/synopsys-usb-otg which should be using repr(C) and isn't.

[antonok-edm]

Indeed, looks like this is related to #102750, and thus a bug in synopsys-usb-otg rather than rust. Sorry for noise!