diff --git a/cpp2rust/compat/errno.h b/cpp2rust/compat/errno.h
new file mode 100644
index 00000000..d6b34c30
--- /dev/null
+++ b/cpp2rust/compat/errno.h
@@ -0,0 +1,10 @@
+// Copyright (c) 2022-present INESC-ID.
+// Distributed under the MIT license that can be found in the LICENSE file.
+
+#include_next <errno.h>
+
+#undef errno
+
+int *cpp2rust_errno(void);
+
+#define errno (*cpp2rust_errno())
diff --git a/libcc2rs/src/compat.rs b/libcc2rs/src/compat.rs
index 486c260b..38873938 100644
--- a/libcc2rs/src/compat.rs
+++ b/libcc2rs/src/compat.rs
@@ -11,6 +11,14 @@ unsafe extern "C" {
     #[cfg(target_os = "macos")]
     #[link_name = "malloc_size"]
     fn platform_malloc_size(ptr: *const c_void) -> usize;
+
+    #[cfg(target_os = "linux")]
+    #[link_name = "__errno_location"]
+    fn platform_errno_location() -> *mut i32;
+
+    #[cfg(target_os = "macos")]
+    #[link_name = "__error"]
+    fn platform_errno_location() -> *mut i32;
 }
 
 /// # Safety
@@ -28,3 +36,10 @@ pub unsafe fn malloc_usable_size(ptr: *mut c_void) -> usize {
         unsafe { platform_malloc_size(ptr as *const c_void) }
     }
 }
+
+/// # Safety
+///
+/// Invokes the platform specific errno.
+pub unsafe fn cpp2rust_errno() -> *mut i32 {
+    unsafe { platform_errno_location() }
+}
diff --git a/rules/errno/ir_unsafe.json b/rules/errno/ir_unsafe.json
new file mode 100644
index 00000000..d910da01
--- /dev/null
+++ b/rules/errno/ir_unsafe.json
@@ -0,0 +1,13 @@
+{
+  "f1": {
+    "body": [
+      {
+        "text": "libcc2rs::cpp2rust_errno()"
+      }
+    ],
+    "return_type": {
+      "type": "*mut i32",
+      "is_unsafe_pointer": true
+    }
+  }
+}
diff --git a/rules/errno/src.c b/rules/errno/src.c
new file mode 100644
index 00000000..0e32ea0e
--- /dev/null
+++ b/rules/errno/src.c
@@ -0,0 +1,6 @@
+// Copyright (c) 2022-present INESC-ID.
+// Distributed under the MIT license that can be found in the LICENSE file.
+
+#include <errno.h>
+
+int *f1(void) { return cpp2rust_errno(); }
diff --git a/rules/errno/tgt_unsafe.rs b/rules/errno/tgt_unsafe.rs
new file mode 100644
index 00000000..57796bc2
--- /dev/null
+++ b/rules/errno/tgt_unsafe.rs
@@ -0,0 +1,6 @@
+// Copyright (c) 2022-present INESC-ID.
+// Distributed under the MIT license that can be found in the LICENSE file.
+
+unsafe fn f1() -> *mut i32 {
+    libcc2rs::cpp2rust_errno()
+}
diff --git a/rules/src/modules.rs b/rules/src/modules.rs
index 6357cfc6..0e9cde66 100644
--- a/rules/src/modules.rs
+++ b/rules/src/modules.rs
@@ -34,6 +34,8 @@ pub mod cstring_tgt_unsafe;
 pub mod deque_tgt_refcount;
 #[path = r#"../deque/tgt_unsafe.rs"#]
 pub mod deque_tgt_unsafe;
+#[path = r#"../errno/tgt_unsafe.rs"#]
+pub mod errno_tgt_unsafe;
 #[path = r#"../fstream/tgt_refcount.rs"#]
 pub mod fstream_tgt_refcount;
 #[path = r#"../fstream/tgt_unsafe.rs"#]
diff --git a/tests/unit/errno.c b/tests/unit/errno.c
new file mode 100644
index 00000000..8a0be0bf
--- /dev/null
+++ b/tests/unit/errno.c
@@ -0,0 +1,40 @@
+// no-compile: refcount
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void test_errno(void) {
+  errno = 0;
+  assert(errno == 0);
+  errno = 42;
+  assert(errno == 42);
+  int saved = errno;
+  assert(saved == 42);
+  errno = 0;
+}
+
+static void test_errno_preserved_across_strdup(void) {
+  errno = 99;
+  char *d = strdup("hello");
+  assert(d != NULL);
+  assert(errno == 99);
+  free(d);
+  errno = 0;
+}
+
+static void test_errno_from_fseek(void) {
+  errno = 0;
+  int r = fseek(stdin, 0, SEEK_SET);
+  assert(r == -1);
+  assert(errno == ESPIPE);
+  errno = 0;
+}
+
+int main(void) {
+  test_errno();
+  test_errno_preserved_across_strdup();
+  test_errno_from_fseek();
+  return 0;
+}
diff --git a/tests/unit/out/unsafe/errno.rs b/tests/unit/out/unsafe/errno.rs
new file mode 100644
index 00000000..d0f8f8e7
--- /dev/null
+++ b/tests/unit/out/unsafe/errno.rs
@@ -0,0 +1,55 @@
+extern crate libc;
+use libc::*;
+extern crate libcc2rs;
+use libcc2rs::*;
+use std::collections::BTreeMap;
+use std::io::{Read, Seek, Write};
+use std::os::fd::{AsFd, FromRawFd, IntoRawFd};
+use std::rc::Rc;
+pub unsafe fn test_errno_0() {
+    (*libcc2rs::cpp2rust_errno()) = 0;
+    assert!(((((*libcc2rs::cpp2rust_errno()) == (0)) as i32) != 0));
+    (*libcc2rs::cpp2rust_errno()) = 42;
+    assert!(((((*libcc2rs::cpp2rust_errno()) == (42)) as i32) != 0));
+    let mut saved: i32 = (*libcc2rs::cpp2rust_errno());
+    assert!(((((saved) == (42)) as i32) != 0));
+    (*libcc2rs::cpp2rust_errno()) = 0;
+}
+pub unsafe fn test_errno_preserved_across_strdup_1() {
+    (*libcc2rs::cpp2rust_errno()) = 99;
+    let mut d: *mut u8 =
+        libc::strdup((b"hello\0".as_ptr().cast_mut()).cast_const() as *const i8) as *mut u8;
+    assert!((((!((d).is_null())) as i32) != 0));
+    assert!(((((*libcc2rs::cpp2rust_errno()) == (99)) as i32) != 0));
+    libc::free((d as *mut u8 as *mut ::libc::c_void));
+    (*libcc2rs::cpp2rust_errno()) = 0;
+}
+pub unsafe fn test_errno_from_fseek_2() {
+    (*libcc2rs::cpp2rust_errno()) = 0;
+    let mut r: i32 = if (match 0 {
+        0 => (*libcc2rs::cin_unsafe()).seek(std::io::SeekFrom::Start(0_i64 as u64)),
+        1 => (*libcc2rs::cin_unsafe()).seek(std::io::SeekFrom::Current(0_i64)),
+        2 => (*libcc2rs::cin_unsafe()).seek(std::io::SeekFrom::End(0_i64)),
+        _ => Err(std::io::Error::other("unsupported whence for fseek.")),
+    })
+    .is_ok()
+    {
+        0
+    } else {
+        -1
+    };
+    assert!(((((r) == (-1_i32)) as i32) != 0));
+    assert!(((((*libcc2rs::cpp2rust_errno()) == (29)) as i32) != 0));
+    (*libcc2rs::cpp2rust_errno()) = 0;
+}
+pub fn main() {
+    unsafe {
+        std::process::exit(main_0() as i32);
+    }
+}
+unsafe fn main_0() -> i32 {
+    (unsafe { test_errno_0() });
+    (unsafe { test_errno_preserved_across_strdup_1() });
+    (unsafe { test_errno_from_fseek_2() });
+    return 0;
+}