diff --git a/compiler/rustc/src/main.rs b/compiler/rustc/src/main.rs
index a55a63a7bf17..ca1bb59e59d6 100644
--- a/compiler/rustc/src/main.rs
+++ b/compiler/rustc/src/main.rs
@@ -65,7 +65,7 @@ fn main() {
         // linking, so we need to explicitly depend on the function.
         #[cfg(target_os = "macos")]
         {
-            extern "C" {
+            unsafe extern "C" {
                 fn _rjem_je_zone_register();
             }
 
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index 9a68eeb3326e..c578eb4dc458 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -308,7 +308,7 @@ impl<'tcx> UniversalRegions<'tcx> {
 
     /// Returns an iterator over all the RegionVids corresponding to
     /// universally quantified free regions.
-    pub(crate) fn universal_regions_iter(&self) -> impl Iterator<Item = RegionVid> {
+    pub(crate) fn universal_regions_iter(&self) -> impl Iterator<Item = RegionVid> + use<> {
         (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::from_usize)
     }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
index 39bac13a9680..9c740ab98688 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
@@ -7,7 +7,7 @@ use super::ffi::{BasicBlock, Metadata, Module, Type, Value};
 use crate::llvm::Bool;
 
 #[link(name = "llvm-wrapper", kind = "static")]
-extern "C" {
+unsafe extern "C" {
     // Enzyme
     pub(crate) fn LLVMRustHasMetadata(I: &Value, KindID: c_uint) -> bool;
     pub(crate) fn LLVMRustEraseInstUntilInclusive(BB: &BasicBlock, I: &Value);
@@ -18,7 +18,7 @@ extern "C" {
     pub(crate) fn LLVMRustVerifyFunction(V: &Value, action: LLVMRustVerifierFailureAction) -> Bool;
 }
 
-extern "C" {
+unsafe extern "C" {
     // Enzyme
     pub(crate) fn LLVMDumpModule(M: &Module);
     pub(crate) fn LLVMDumpValue(V: &Value);
diff --git a/compiler/rustc_data_structures/src/graph/scc/mod.rs b/compiler/rustc_data_structures/src/graph/scc/mod.rs
index 93f6192b10b0..2241b538738c 100644
--- a/compiler/rustc_data_structures/src/graph/scc/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/scc/mod.rs
@@ -133,7 +133,7 @@ impl<N: Idx, S: Idx + Ord, A: Annotation> Sccs<N, S, A> {
     /// meaning that if `S1 -> S2`, we will visit `S2` first and `S1` after.
     /// This is convenient when the edges represent dependencies: when you visit
     /// `S1`, the value for `S2` will already have been computed.
-    pub fn all_sccs(&self) -> impl Iterator<Item = S> {
+    pub fn all_sccs(&self) -> impl Iterator<Item = S> + use<N, S, A> {
         (0..self.scc_data.len()).map(S::new)
     }
 
diff --git a/compiler/rustc_expand/src/proc_macro.rs b/compiler/rustc_expand/src/proc_macro.rs
index dca0516f9f3b..814d2b04d8d0 100644
--- a/compiler/rustc_expand/src/proc_macro.rs
+++ b/compiler/rustc_expand/src/proc_macro.rs
@@ -31,7 +31,7 @@ impl<T> pm::bridge::server::MessagePipe<T> for MessagePipe<T> {
     }
 }
 
-fn exec_strategy(ecx: &ExtCtxt<'_>) -> impl pm::bridge::server::ExecutionStrategy {
+fn exec_strategy(ecx: &ExtCtxt<'_>) -> impl pm::bridge::server::ExecutionStrategy + use<> {
     pm::bridge::server::MaybeCrossThread::<MessagePipe<_>>::new(
         ecx.sess.opts.unstable_opts.proc_macro_execution_strategy
             == ProcMacroExecutionStrategy::CrossThread,
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index d70d9d344b94..2d3c7f834e98 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -171,13 +171,15 @@ fn configure_and_expand(
                     new_path.push(path);
                 }
             }
-            env::set_var(
-                "PATH",
-                &env::join_paths(
-                    new_path.iter().filter(|p| env::join_paths(iter::once(p)).is_ok()),
-                )
-                .unwrap(),
-            );
+            unsafe {
+                env::set_var(
+                    "PATH",
+                    &env::join_paths(
+                        new_path.iter().filter(|p| env::join_paths(iter::once(p)).is_ok()),
+                    )
+                    .unwrap(),
+                );
+            }
         }
 
         // Create the config for macro expansion
@@ -216,7 +218,9 @@ fn configure_and_expand(
         }
 
         if cfg!(windows) {
-            env::set_var("PATH", &old_path);
+            unsafe {
+                env::set_var("PATH", &old_path);
+            }
         }
 
         krate
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index 48806888b43d..3d1f3b2cd4dd 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -51,9 +51,13 @@ fn detect_llvm_link() -> (&'static str, &'static str) {
 fn restore_library_path() {
     let key = tracked_env_var_os("REAL_LIBRARY_PATH_VAR").expect("REAL_LIBRARY_PATH_VAR");
     if let Some(env) = tracked_env_var_os("REAL_LIBRARY_PATH") {
-        env::set_var(&key, env);
+        unsafe {
+            env::set_var(&key, env);
+        }
     } else {
-        env::remove_var(&key);
+        unsafe {
+            env::remove_var(&key);
+        }
     }
 }