Fix compilation under wasm32-wasi under various feature combinations. (…

…#960)

src/maybe_polyfill/no_std/os/fd/owned.rs

@@ -112,12 +112,11 @@ impl OwnedFd {
         Ok(fd.into())
     }
 
+    /// Creates a new `OwnedFd` instance that shares the same underlying file handle
+    /// as the existing `OwnedFd` instance.
     #[cfg(target_arch = "wasm32")]
     pub fn try_clone(&self) -> crate::io::Result<Self> {
-        Err(crate::io::const_io_error!(
-            crate::io::ErrorKind::Unsupported,
-            "operation not supported on WASI yet",
-        ))
+        Err(crate::io::Errno::NOSYS)
     }
 }
 
@@ -150,10 +149,7 @@ impl BorrowedFd<'_> {
     #[cfg(any(target_arch = "wasm32", target_os = "hermit"))]
     #[cfg_attr(staged_api, stable(feature = "io_safety", since = "1.63.0"))]
     pub fn try_clone_to_owned(&self) -> crate::io::Result<OwnedFd> {
-        Err(crate::io::const_io_error!(
-            crate::io::ErrorKind::Unsupported,
-            "operation not supported on WASI yet",
-        ))
+        Err(crate::io::Errno::NOSYS)
     }
 }
 

src/param/mod.rs

@@ -6,9 +6,9 @@
 //! between different processes on the same system.
 
 mod auxv;
-#[cfg(feature = "use-explicitly-provided-auxv")]
+#[cfg(all(feature = "use-explicitly-provided-auxv", not(libc)))]
 mod init;
 
 pub use auxv::*;
-#[cfg(feature = "use-explicitly-provided-auxv")]
+#[cfg(all(feature = "use-explicitly-provided-auxv", not(libc)))]
 pub use init::init;

src/path/arg.rs

@@ -1063,10 +1063,12 @@ where
 
     #[cfg(not(feature = "alloc"))]
     {
-        #[cfg(libc)]
+        #[cfg(all(libc, not(target_os = "wasi")))]
         const LARGE_PATH_BUFFER_SIZE: usize = libc::PATH_MAX as usize;
         #[cfg(linux_raw)]
         const LARGE_PATH_BUFFER_SIZE: usize = linux_raw_sys::general::PATH_MAX as usize;
+        #[cfg(target_os = "wasi")]
+        const LARGE_PATH_BUFFER_SIZE: usize = 4096 as usize; // TODO: upstream this
 
         // Taken from
         // <https://github.com/rust-lang/rust/blob/a00f8ba7fcac1b27341679c51bf5a3271fa82df3/library/std/src/sys/common/small_c_string.rs>