Add doc(cfg()) noting that some functions need nightly

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

Cargo.toml

@@ -42,6 +42,9 @@ inline_asm = []
 abi_x86_interrupt = []
 const_fn = []
 
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]
+
 [package.metadata.release]
 no-dev-version = true
 pre-release-replacements = [

src/instructions/interrupts.rs

@@ -152,19 +152,14 @@ pub fn int3() {
 /// This currently needs to be a macro because the `int` argument needs to be an
 /// immediate. This macro will be replaced by a generic function when support for
 /// const generics is implemented in Rust.
-#[cfg(feature = "inline_asm")]
+#[cfg_attr(docsrs, doc(cfg(feature = "nightly")))]
 #[macro_export]
 macro_rules! software_interrupt {
     ($x:expr) => {{
+        #[cfg(feature = "inline_asm")]
         asm!("int {id}", id = const $x, options(nomem, nostack));
-    }};
-}
 
-/// Not implemented
-#[cfg(not(feature = "inline_asm"))]
-#[macro_export]
-macro_rules! software_interrupt {
-    ($x:expr) => {{
-        compile_error!("software_interrupt not implemented for non-nightly");
+        #[cfg(not(feature = "inline_asm"))]
+        compile_error!("software_interrupt!() requires \"nightly\" feature");
     }};
 }

src/instructions/mod.rs

@@ -53,14 +53,16 @@ pub fn bochs_breakpoint() {
 
 /// Gets the current instruction pointer. Note that this is only approximate as it requires a few
 /// instructions to execute.
-#[cfg(feature = "inline_asm")]
+#[cfg_attr(docsrs, doc(cfg(feature = "nightly")))]
 #[inline(always)]
 pub fn read_rip() -> crate::VirtAddr {
     let rip: u64;
+    #[cfg(feature = "inline_asm")]
     unsafe {
-        asm!(
-            "lea {}, [rip]", out(reg) rip, options(nostack, nomem, preserves_flags)
-        );
+        asm!("lea {}, [rip]", out(reg) rip, options(nostack, nomem, preserves_flags));
     }
+
+    #[cfg(not(feature = "inline_asm"))]
+    compile_error!("read_rip() requires \"nightly\" feature");
     crate::VirtAddr::new(rip)
 }

src/lib.rs

@@ -8,6 +8,7 @@
 #![cfg_attr(feature = "const_fn", feature(const_fn_trait_bound))]
 #![cfg_attr(feature = "inline_asm", feature(asm))]
 #![cfg_attr(feature = "abi_x86_interrupt", feature(abi_x86_interrupt))]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 #![warn(missing_docs)]
 #![deny(missing_debug_implementations)]