std: Fix some behavior without stdio handles

On all platforms, reading from stdin where the actual stdin isn't present should
return 0 bytes as having been read rather than the entire buffer.

On Windows, handle the case where we're inheriting stdio handles but one of them
isn't present. Currently the behavior is to fail returning an I/O error but
instead this commit corrects it to detecting this situation and propagating the
non-set handle.

Closes #31167

1 files changed, 8 insertions, 3 deletions

diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index e0f8d6f9df9..61f73b00265 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -351,10 +351,15 @@ fn make_dirp(d: Option<&OsString>) -> (*const u16, Vec<u16>) {
 impl Stdio {
     fn to_handle(&self, stdio_id: c::DWORD) -> io::Result<Handle> {
         match *self {
+            // If no stdio handle is available, then inherit means that it
+            // should still be unavailable so propagate the
+            // INVALID_HANDLE_VALUE.
             Stdio::Inherit => {
-                stdio::get(stdio_id).and_then(|io| {
-                    io.handle().duplicate(0, true, c::DUPLICATE_SAME_ACCESS)
-                })
+                match stdio::get(stdio_id) {
+                    Ok(io) => io.handle().duplicate(0, true,
+                                                    c::DUPLICATE_SAME_ACCESS),
+                    Err(..) => Ok(Handle::new(c::INVALID_HANDLE_VALUE)),
+                }
             }
             Stdio::Raw(handle) => {
                 RawHandle::new(handle).duplicate(0, true, c::DUPLICATE_SAME_ACCESS)