main() calling convention discrepancy

[mciantyre]

The documentation notes that main()'s signature is expected to be extern "C" fn () -> !. The docs say that users could define main() by using the #[entry] macro on a function, or by manually defining a function with that name and calling convention.

cortex-m-rt/src/lib.rs

Lines 256 to 257 in ef6c6e6

	//! The unmangled `main` symbol must have signature `extern "C" fn() -> !` or its invocation from
	//! `Reset` will result in undefined behavior.

The documentation conforms with the #[entry] macro implementation, which creates a symbol main() as using C calling conventions:

cortex-m-rt/macros/src/lib.rs

Lines 100 to 112 in ef6c6e6

	quote!(
	#(#cfgs)*
	#(#attrs)*
	#[doc(hidden)]
	#[export_name = "main"]
	pub unsafe extern "C" fn #tramp_ident() {
	#ident(
	#(#resource_args),*
	)
	}
	#f
	)

However, in Reset(), we qualify main() as using Rust calling conventions:

cortex-m-rt/src/lib.rs

Lines 902 to 908 in ef6c6e6

	extern "Rust" {
	// This symbol will be provided by the user via `#[entry]`
	fn main() -> !;
	// This symbol will be provided by the user via `#[pre_init]`
	fn __pre_init();
	}

Should we qualify main() as extern "C" in Reset()?

[mciantyre]

We qualified main() as extern "C".