add support for the tempfile crate

src/shims/unix/fs.rs

@@ -585,8 +585,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 );
             };
 
-            if mode != 0o666 {
-                throw_unsup_format!("non-default mode 0o{:o} is not supported", mode);
+            // currently we only support that the owner must always have
+            // read-write permissions and that none of the owner, group
+            // and other may have execute permissions.
+            let owner_has_read_write_permissions = mode & 0o600 == 0o600;
+            let has_any_execute_permissions = mode & 0o111 != 0;
+            if !owner_has_read_write_permissions || has_any_execute_permissions {
+                throw_unsup_format!("mode 0o{:o} is not supported", mode);
             }
 
             mirror |= o_creat;

test_dependencies/Cargo.toml

@@ -13,6 +13,7 @@ tokio = { version = "1.0", features = ["full"] }
 libc = "0.2"
 page_size = "0.5"
 num_cpus = "1.10.1"
+tempfile = "3"
 
 getrandom_1 = { package = "getrandom", version = "0.1" }
 getrandom = { version = "0.2" }

tests/pass-dep/tempfile.rs

@@ -0,0 +1,39 @@
+//@ignore-target-windows: no libc on Windows
+//@compile-flags: -Zmiri-disable-isolation
+
+use std::ffi::{CStr, CString};
+use std::path::PathBuf;
+
+/// Test that the [`tempfile`] crate is compatible with miri.
+fn main() {
+    // test_tempfile(); // does not work when host!=target
+    test_tempfile_in();
+}
+
+fn tmp() -> PathBuf {
+    let path = std::env::var("MIRI_TEMP")
+        .unwrap_or_else(|_| std::env::temp_dir().into_os_string().into_string().unwrap());
+    // These are host paths. We need to convert them to the target.
+    let path = CString::new(path).unwrap();
+    let mut out = Vec::with_capacity(1024);
+
+    unsafe {
+        extern "Rust" {
+            fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
+        }
+        let ret = miri_host_to_target_path(path.as_ptr(), out.as_mut_ptr(), out.capacity());
+        assert_eq!(ret, 0);
+        let out = CStr::from_ptr(out.as_ptr()).to_str().unwrap();
+        PathBuf::from(out)
+    }
+}
+
+// does not work when host!=target:
+// fn test_tempfile() {
+//     tempfile::tempfile().unwrap();
+// }
+
+fn test_tempfile_in() {
+    let dir_path = tmp();
+    tempfile::tempfile_in(dir_path).unwrap();
+}