Add OsString from/to bytes helper functions

Author: pvdrz

src/helpers.rs

@@ -1,4 +1,5 @@
 use std::mem;
+use std::ffi::OsString;
 
 use rustc::ty::{self, layout::{self, Size, Align}};
 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
@@ -305,3 +306,25 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         self.eval_libc(name)?.to_i32()
     }
 }
+
+
+pub fn bytes_to_os_string<'tcx>(bytes: Vec<u8>) -> InterpResult<'tcx, OsString> {
+        if cfg!(unix) {
+            Ok(std::os::unix::ffi::OsStringExt::from_vec(bytes))
+        } else {
+            std::str::from_utf8(&bytes)
+                .map_err(|_| err_unsup_format!("{:?} is not a valid utf-8 string", bytes).into())
+                .map(OsString::from)
+        }
+    }
+
+pub fn os_string_to_bytes<'tcx>(os_string: OsString) -> InterpResult<'tcx, Vec<u8>> {
+        if cfg!(unix) {
+            Ok(std::os::unix::ffi::OsStringExt::into_vec(os_string))
+        } else {
+            os_string
+                .into_string()
+                .map_err(|os_string| err_unsup_format!("{:?} is not a valid utf-8 string", os_string).into())
+                .map(|s| s.into_bytes())
+        }
+    }

src/shims/env.rs

@@ -1,9 +1,9 @@
 use std::collections::HashMap;
 use std::env;
-use std::path::Path;
 
 use crate::stacked_borrows::Tag;
 use crate::*;
+
 use rustc::ty::layout::Size;
 use rustc_mir::interpret::{Memory, Pointer};
 
@@ -132,7 +132,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         match env::current_dir() {
             Ok(cwd) => {
                 // It is not clear what happens with non-utf8 paths here
-                let mut bytes = cwd.display().to_string().into_bytes();
+                let mut bytes = helpers::os_string_to_bytes(cwd.into())?;
                 // If `size` is smaller or equal than the `bytes.len()`, writing `bytes` plus the
                 // required null terminator to memory using the `buf` pointer would cause an
                 // overflow. The desired behavior in this case is to return null.
@@ -162,16 +162,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             throw_unsup_format!("`chdir` not available when isolation is enabled")
         }
 
-        let path_bytes = this
-            .memory()
-            .read_c_str(this.read_scalar(path_op)?.not_undef()?)?;
-
-        let path = Path::new(
-            std::str::from_utf8(path_bytes)
-                .map_err(|_| err_unsup_format!("{:?} is not a valid utf-8 string", path_bytes))?,
-        );
+        let bytes = this.memory().read_c_str(this.read_scalar(path_op)?.not_undef()?)?;
+        let path = helpers::bytes_to_os_string(bytes.to_vec());
 
-        match env::set_current_dir(path) {
+        match env::set_current_dir(path?) {
             Ok(()) => Ok(0),
             Err(e) => {
                 this.consume_io_error(e)?;

src/shims/fs.rs

@@ -67,11 +67,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             options.create(true);
         }
 
-        let path_bytes = this
+        let bytes = this
             .memory()
             .read_c_str(this.read_scalar(path_op)?.not_undef()?)?;
-        let path = std::str::from_utf8(path_bytes)
-            .map_err(|_| err_unsup_format!("{:?} is not a valid utf-8 string", path_bytes))?;
+        let path: std::path::PathBuf = helpers::bytes_to_os_string(bytes.to_vec())?.into();
 
         let fd = options.open(path).map(|file| {
             let mut fh = &mut this.machine.file_handler;