add support for the tempfile crate

tests/pass-dep/shims/libc-fs.rs

@@ -20,7 +20,6 @@ fn main() {
     test_file_open_unix_extra_third_arg();
     #[cfg(target_os = "linux")]
     test_o_tmpfile_flag();
-    test_tempfile();
 }
 
 fn tmp() -> PathBuf {
@@ -167,9 +166,3 @@ fn test_o_tmpfile_flag() {
             .raw_os_error(),
     );
 }
-
-/// Test that the [`tempfile`] crate is compatible with miri.
-fn test_tempfile() {
-    let dir_path = tmp();
-    tempfile::tempfile_in(dir_path).unwrap();
-}

tests/pass-dep/tempfile.rs

@@ -0,0 +1,34 @@
+//@ignore-target-windows: no libc on Windows
+//@compile-flags: -Zmiri-disable-isolation
+
+//! Test that the [`tempfile`] crate is compatible with miri.
+fn main() {
+    test_tempfile();
+    test_tempfile_in();
+}
+
+fn tmp() -> PathBuf {
+    std::env::var("MIRI_TEMP")
+        .map(|tmp| {
+            // MIRI_TEMP is set outside of our emulated
+            // program, so it may have path separators that don't
+            // correspond to our target platform. We normalize them here
+            // before constructing a `PathBuf`
+
+            #[cfg(windows)]
+            return PathBuf::from(tmp.replace("/", "\\"));
+
+            #[cfg(not(windows))]
+            return PathBuf::from(tmp.replace("\\", "/"));
+        })
+        .unwrap_or_else(|_| std::env::temp_dir())
+}
+
+fn test_tempfile() {
+    tempfile::tempfile().unwrap();
+}
+
+fn test_tempfile_in() {
+    let dir_path = tmp();
+    tempfile::tempfile_in(dir_path).unwrap();
+}