fallback to procfs

Author: devnexen

library/std/src/sys/pal/unix/fs.rs

@@ -1498,6 +1498,16 @@ impl fmt::Debug for File {
             let mut buf = vec![0; libc::PATH_MAX as usize];
             let n = unsafe { libc::fcntl(fd, libc::F_GETPATH, buf.as_ptr()) };
             if n == -1 {
+                cfg_if::cfg_if! {
+                    if #[cfg(target_os = "netbsd")] {
+                        // fallback to procfs as last resort
+                        let mut p = PathBuf::from("/proc/self/fd");
+                        p.push(&fd.to_string());
+                        if p.exists() {
+                            return readlink(&p).ok();
+                        }
+                    }
+                }
                 return None;
             }
             let l = buf.iter().position(|&c| c == 0).unwrap();