Make code work with optimization

[Tiwalun]

First of all, thanks for writing this book, it was a great help getting Rust code to run on my Cortex M4. 👍

While experimenting with my code, I found a way how it can be compiled with optimization, without everything being optimized away.

The following steps have to be done:

• Make mod vector_table, static EXCEPTIONS and static RESET public
• Add the #[no_mangle] attribute to EXCEPTIONS and RESET
• use core::ptr::read_volatile and write_volatile for peripheral access

If this looks okay, I'll make a pull request with these changes.

[japaric]

First of all, thanks for writing this book, it was a great help getting Rust code to run on my Cortex M4

You are welcome!

While experimenting with my code, I found a way how it can be compiled with optimization, without everything being optimized away.

This is exactly the topic of the next chapter!

The following steps have to be done:

Sounds about right! One more thing you can do is add assertions to the linker scripts to statically "prevent" (you get linker errors) symbols from being stripped.

I'll make a pull request with these changes.

Thanks! I appreciate the sentiment, but I want to explain what volatile read/writes are and make these changes in another chapter and not in the existing one.