Blink test

[cmcavity]

After the update to the Tock submodule, the blink test now fails to compile.

tock-teensy/boards/teensy/src/tests/mod.rs

Lines 20 to 26 in 5019b78

	// Set this function to run whatever test you desire. Test functions are named XXX_test by convention.
	pub fn test() {
	spi::spi_test();
	}
	// Set this to true to make the kernel run the test instead of main.
	pub const TEST: bool = false;

When this code is changed to run blink::blink_test(), we get the output: "error: linking with arm-none-eabi-gcc failed: exit code: 1".

This is the blink test:

tock-teensy/boards/teensy/src/tests/blink.rs

Lines 14 to 19 in 5019b78

	pub fn blink_test() {
	loop {
	led_toggle();
	delay();
	}
	}

If we change the test to use for _ in 1..1000_000 {} instead of loop {}, it compiles and passes, but it is unclear why the use of loop {} causes a compile error.

[alevy]

I'm not able to reproduce this. It compiles fine for me with the blink_test replacing the spi_test. Are you certain you're using the right version of Rust? Maybe a make clean first?

[cmcavity]

Did you also change line 26 to pub const TEST: bool = true; ?

[alevy]

OK, got it now. It's not exactly a compilation error, it's a link time error, and it could be useful to include the linker error:

  = note: /var/local/alevy/hack/helena/tock-teensy/boards/teensy/target/thumbv7em-none-eabi/release/deps/teensy-2fd7a6e3494a6943.teensy0.rcgu.o: In function `mk66::hard_fault_handler':
          teensy0-e3f15d6091c6d8ba2affd3b5a05ecb68.rs:(.text._ZN4mk6618hard_fault_handler17h661e85eb5618eaeaE+0x384): undefined reference to `SYSCALL_FIRED'
          teensy0-e3f15d6091c6d8ba2affd3b5a05ecb68.rs:(.text._ZN4mk6618hard_fault_handler17h661e85eb5618eaeaE+0x388): undefined reference to `APP_FAULT'
          /var/local/alevy/hack/helena/tock-teensy/boards/teensy/target/thumbv7em-none-eabi/release/deps/teensy-2fd7a6e3494a6943.teensy0.rcgu.o: In function `to_kernel':
          teensy0-e3f15d6091c6d8ba2affd3b5a05ecb68.rs:(.text._ZN8cortexm411svc_handler17h3f9d44e363dd8ae7E+0x34): undefined reference to `SYSCALL_FIRED'
          collect2: error: ld returned 1 exit status

What's happening is it's not finding the symbols SYSCALL_FIRED and APP_FAULT, which are declared in the kernel::process.

The reason loop vs for _ 0..1000 makes a difference is that in the second case, the test terminates, while in the first it doesn't. If it doesn't terminate, because it's called before the kernel's main loop, the compiler will decide that there is no way to reach code that uses that symbol in the kernel crate, and elide the symbol from the object file.

The fix for this is to mark each of those symbols as #[used] in process.rs (tested and confirmed), but meanwhile, is there a reason for the blink test to never terminate? Why not adapt the blink example from the course that uses a timer and is asynchronous?

[cmcavity]

Could you point me to that blink example?