From b73696d95fa05f330ffd519717726f00dfb4214b Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 12 May 2026 09:26:03 +0200
Subject: [PATCH 1/3] add test for env::temp_dir

---
 tests/pass/shims/env/temp.rs | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 tests/pass/shims/env/temp.rs

diff --git a/tests/pass/shims/env/temp.rs b/tests/pass/shims/env/temp.rs
new file mode 100644
index 0000000000..815e0b8827
--- /dev/null
+++ b/tests/pass/shims/env/temp.rs
@@ -0,0 +1,9 @@
+//@compile-flags: -Zmiri-disable-isolation
+use std::env;
+
+fn main() {
+    // If this is set it may hide calling some shims.
+    unsafe { env::remove_var("TMPDIR") };
+
+    let _path = env::temp_dir();
+}

From 84a4a2711702423bb08bf224ea56dba07aba3329 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 12 May 2026 16:51:00 +0200
Subject: [PATCH 2/3] implement GetTempPathW on Windows

---
 src/shims/windows/env.rs           | 21 +++++++++++++++++++++
 src/shims/windows/foreign_items.rs | 11 +++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/shims/windows/env.rs b/src/shims/windows/env.rs
index aabace4b7c..f203a6833a 100644
--- a/src/shims/windows/env.rs
+++ b/src/shims/windows/env.rs
@@ -256,4 +256,25 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
         })
     }
+
+    #[allow(non_snake_case)]
+    fn GetTempPathW(
+        &mut self,
+        buflen: &OpTy<'tcx>, // DWORD
+        buf: &OpTy<'tcx>,    // LPWSTR
+    ) -> InterpResult<'tcx, Scalar> // returns DWORD
+    {
+        let this = self.eval_context_mut();
+        this.assert_target_os(Os::Windows, "GetTempPathW");
+        this.check_no_isolation("`GetTempPathW`")?;
+
+        let buflen = this.read_scalar(buflen)?.to_u32()?;
+        let buf = this.read_pointer(buf)?;
+
+        let temp_dir = env::temp_dir();
+
+        return interp_ok(Scalar::from_u32(windows_check_buffer_size(
+            this.write_path_to_wide_str(&temp_dir, buf, buflen.into())?,
+        )));
+    }
 }
diff --git a/src/shims/windows/foreign_items.rs b/src/shims/windows/foreign_items.rs
index c378312633..ba26a55c2c 100644
--- a/src/shims/windows/foreign_items.rs
+++ b/src/shims/windows/foreign_items.rs
@@ -235,6 +235,17 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.GetCurrentProcessId()?;
                 this.write_scalar(result, dest)?;
             }
+            "GetTempPathW" => {
+                // FIXME: This does not have a direct test (#3179).
+                let [bufferlength, buffer] = this.check_shim_sig(
+                    shim_sig!(extern "system" fn(u32, *mut _) -> u32),
+                    link_name,
+                    abi,
+                    args,
+                )?;
+                let result = this.GetTempPathW(bufferlength, buffer)?;
+                this.write_scalar(result, dest)?;
+            }
 
             // File related shims
             "NtWriteFile" => {

From 481f75d70e186db0ce62b90144af8e290f818032 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 12 May 2026 17:02:36 +0200
Subject: [PATCH 3/3] stub out confstr for macOS temp_dir

---
 src/shims/unix/fs.rs                  |  4 ++--
 src/shims/unix/macos/foreign_items.rs | 10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/shims/unix/fs.rs b/src/shims/unix/fs.rs
index f87e12bd50..0caae04d93 100644
--- a/src/shims/unix/fs.rs
+++ b/src/shims/unix/fs.rs
@@ -871,7 +871,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let permissions = this.host_permissions_from_mode(mode.try_into().unwrap())?;
         if let Err(err) = fs::set_permissions(path, permissions) {
-            return this.set_last_error_and_return_i32(IoError::HostError(err));
+            return this.set_last_error_and_return_i32(err);
         }
 
         interp_ok(Scalar::from_i32(0))
@@ -899,7 +899,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let permissions = this.host_permissions_from_mode(mode.try_into().unwrap())?;
         if let Err(err) = file.file.set_permissions(permissions) {
-            return this.set_last_error_and_return_i32(IoError::HostError(err));
+            return this.set_last_error_and_return_i32(err);
         }
 
         interp_ok(Scalar::from_i32(0))
diff --git a/src/shims/unix/macos/foreign_items.rs b/src/shims/unix/macos/foreign_items.rs
index a979c88def..d8146ab7b8 100644
--- a/src/shims/unix/macos/foreign_items.rs
+++ b/src/shims/unix/macos/foreign_items.rs
@@ -328,6 +328,16 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 )?;
             }
 
+            // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
+            // These shims are enabled only when the caller is in the standard library.
+            "confstr" => {
+                let [_key, _buf, _buflen] =
+                    this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
+                // We just pretend that no configuration key exists, and return EINVAL.
+                this.set_last_error(LibcError("EINVAL"))?;
+                this.write_null(dest)?;
+            }
+
             _ => return interp_ok(EmulateItemResult::NotSupported),
         };