Remove non-portable use of fstatat

Part of #10634

src/libc.c

@@ -1,4 +1,5 @@
 #include <dirent.h>
+#include <fcntl.h>
 #include <locale.h>
 #include <paths.h>
 #include <stdbool.h>
@@ -6,6 +7,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/resource.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
@@ -198,3 +200,14 @@ bool C_portable_readdir(DIR* dirp, const char** d_name, size_t* d_name_len, uint
     *d_type = dent->d_type;
     return true;
 }
+
+bool C_portable_fstatat(int dirfd, const char* file, int flag, uint64_t* st_dev, uint64_t* st_ino, mode_t* st_mode) {
+    struct stat buf;
+    if (fstatat(dirfd, file, &buf, flag) == -1) {
+        return false;
+    }
+    *st_dev = buf.st_dev;
+    *st_ino = buf.st_ino;
+    *st_mode = buf.st_mode;
+    return true;
+}

src/libc.rs

@@ -1,4 +1,4 @@
-use std::sync::atomic::AtomicPtr;
+use std::{ffi::CStr, sync::atomic::AtomicPtr};
 
 use libc::{c_char, c_int};
 use once_cell::sync::Lazy;
@@ -79,3 +79,36 @@ fn C_portable_readdir(
         d_type: *mut u8,
     ) -> bool;
 }
+
+pub(crate) fn portable_fstatat(
+    dirfd: c_int,
+    file: &CStr,
+    flag: c_int,
+) -> Option<(u64, u64, libc::mode_t)> {
+    let mut st_dev = unsafe { std::mem::zeroed() };
+    let mut st_ino = unsafe { std::mem::zeroed() };
+    let mut st_mode = unsafe { std::mem::zeroed() };
+    if !unsafe {
+        C_portable_fstatat(
+            dirfd,
+            file.as_ptr(),
+            flag,
+            &mut st_dev,
+            &mut st_ino,
+            &mut st_mode,
+        )
+    } {
+        return None;
+    }
+    Some((st_dev, st_ino, st_mode))
+}
+extern "C" {
+    fn C_portable_fstatat(
+        dirfd: c_int,
+        file: *const c_char,
+        flag: c_int,
+        st_dev: *mut u64,
+        st_ino: *mut u64,
+        st_mode: *mut libc::mode_t,
+    ) -> bool;
+}

src/wutil/dir_iter.rs

@@ -1,6 +1,6 @@
 use super::wopendir;
 use crate::common::{cstr2wcstring, wcs2zstring};
-use crate::libc::portable_readdir;
+use crate::libc::{portable_fstatat, portable_readdir};
 use crate::wchar::{wstr, WString};
 use crate::wutil::DevInode;
 use libc::{
@@ -104,14 +104,13 @@ fn do_stat(&self) {
             return;
         }
         let narrow = wcs2zstring(&self.name);
-        let mut s: libc::stat = unsafe { std::mem::zeroed() };
-        if unsafe { libc::fstatat(fd, narrow.as_ptr(), &mut s, 0) } == 0 {
+        if let Some((st_dev, st_ino, st_mode)) = portable_fstatat(fd, &narrow, 0) {
             let dev_inode = DevInode {
-                device: s.st_dev as u64,
-                inode: s.st_ino as u64,
+                device: st_dev,
+                inode: st_ino,
             };
             self.dev_inode.set(Some(dev_inode));
-            self.typ.set(stat_mode_to_entry_type(s.st_mode));
+            self.typ.set(stat_mode_to_entry_type(st_mode));
         } else {
             match errno::errno().0 {
                 ELOOP => {