Merge pull request #1098 from stlankes/no_std

introduce feature flag `nostd` to boot the kernel without `std`

Cargo.toml

@@ -65,6 +65,7 @@ udp = ["smoltcp", "smoltcp/socket-udp"]
 trace = []
 vga = []
 common-os = []
+nostd = []
 semihosting = ["dep:semihosting"]
 shell = ["simple-shell"]
 

src/errno.rs

@@ -396,11 +396,15 @@ pub const ERFKILL: i32 = 132;
 /// Robust mutexes: Memory page has hardware error
 pub const EHWPOISON: i32 = 133;
 
-#[cfg(all(not(feature = "common-os"), not(target_arch = "riscv64")))]
+#[cfg(all(
+	not(any(feature = "common-os", feature = "nostd")),
+	not(target_arch = "riscv64")
+))]
 #[thread_local]
 pub(crate) static ERRNO: core::cell::UnsafeCell<i32> = core::cell::UnsafeCell::new(0);
 
 /// Get the error number from the thread local storage
+#[cfg(not(feature = "nostd"))]
 #[no_mangle]
 pub extern "C" fn sys_get_errno() -> i32 {
 	cfg_if::cfg_if! {
@@ -423,7 +427,7 @@ pub(crate) trait ToErrno {
 	{
 		if let Some(errno) = self.to_errno() {
 			cfg_if::cfg_if! {
-				if #[cfg(any(feature = "common-os", target_arch = "riscv64"))] {
+				if #[cfg(any(feature = "common-os", feature = "nostd", target_arch = "riscv64"))] {
 					let _ = errno;
 				} else {
 					unsafe {

src/lib.rs

@@ -252,9 +252,9 @@ pub(crate) extern "C" fn __sys_free(ptr: *mut u8, size: usize, align: usize) {
 #[cfg(target_os = "none")]
 extern "C" fn initd(_arg: usize) {
 	extern "C" {
-		#[cfg(all(not(test), not(feature = "common-os")))]
+		#[cfg(all(not(test), not(any(feature = "nostd", feature = "common-os"))))]
 		fn runtime_entry(argc: i32, argv: *const *const u8, env: *const *const u8) -> !;
-		#[cfg(all(not(test), feature = "common-os"))]
+		#[cfg(all(not(test), any(feature = "nostd", feature = "common-os")))]
 		fn main(argc: i32, argv: *const *const u8, env: *const *const u8);
 		#[cfg(feature = "newlib")]
 		fn init_lwip();
@@ -298,9 +298,9 @@ extern "C" fn initd(_arg: usize) {
 	#[cfg(not(test))]
 	unsafe {
 		// And finally start the application.
-		#[cfg(all(not(test), not(feature = "common-os")))]
+		#[cfg(all(not(test), not(any(feature = "nostd", feature = "common-os"))))]
 		runtime_entry(argc, argv, environ);
-		#[cfg(all(not(test), feature = "common-os"))]
+		#[cfg(all(not(test), any(feature = "nostd", feature = "common-os")))]
 		main(argc, argv, environ);
 	}
 	#[cfg(test)]