baremetal Hello World in Rust

This example demonstrates how to create a simple “Hello World” program in Rust for a bare-metal environment. The program is compiled using the rustc compiler directly, without relying on any operating system or standard library.

The key aspects of this example include:

• No Standard Library: The program uses the #![no_std] attribute, which means it does not link against the standard library. This is essential for bare-metal programming where the standard library is not available.

• No Main Function: The program uses the #![no_main] attribute, which indicates that the program does not have a standard main function. Instead, it defines a custom entry point.

• Panic Handler: A custom panic handler is defined using the #[panic_handler] attribute. This handler is called when a panic occurs, and in this case, it enters an infinite loop to halt the program.

• C Interoperability: The program uses the extern “C” block to declare the printf function from the C standard library. This allows the Rust program to call C functions directly.

• Entry Point: The hello_rust_main function is the entry point of the program. It is marked with #[no_mangle] to prevent the Rust compiler from mangling its name, making it callable from C.

• Printing: The program uses the printf function to print “Hello, Rust!!” to the console. The printf function is called using the unsafe block because it involves calling a C function.

This example is a great starting point for understanding how to write and compile Rust programs for bare-metal environments, where you have full control over the hardware and no operating system overhead.