diff --git a/src/header/signal/mod.rs b/src/header/signal/mod.rs
index 858d5ed474..a1913a0c09 100644
--- a/src/header/signal/mod.rs
+++ b/src/header/signal/mod.rs
@@ -292,6 +292,7 @@ pub extern "C" fn sigignore(sig: c_int) -> c_int {
 /// See <https://pubs.opengroup.org/onlinepubs/9699919799/functions/siginterrupt.html>.
 ///
 /// Marked obsolescent in issue 7. Removed in issue 8.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub extern "C" fn siginterrupt(sig: c_int, flag: c_int) -> c_int {
     let mut psa = mem::MaybeUninit::<sigaction>::uninit();
diff --git a/src/header/stdio/mod.rs b/src/header/stdio/mod.rs
index 069d45562a..0ece8d2ed8 100644
--- a/src/header/stdio/mod.rs
+++ b/src/header/stdio/mod.rs
@@ -315,6 +315,7 @@ pub unsafe extern "C" fn ctermid(s: *mut c_char) -> *mut c_char {
 ///
 /// Marked legacy in SUS Version 2.
 // #[unsafe(no_mangle)]
+#[deprecated]
 pub unsafe extern "C" fn cuserid(s: *mut c_char) -> *mut c_char {
     let mut buf: Vec<c_char> = vec![0; 256];
     let mut pwd: pwd::passwd = unsafe { mem::zeroed() };
@@ -894,6 +895,7 @@ pub unsafe extern "C" fn getchar_unlocked() -> c_int {
 /// `fgets` is recommended instead, which is what this implementation calls.
 ///
 /// Get a string from `stdin`
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn gets(s: *mut c_char) -> *mut c_char {
     unsafe { fgets(s, c_int::MAX, &raw mut *stdin) }
@@ -904,6 +906,7 @@ pub unsafe extern "C" fn gets(s: *mut c_char) -> *mut c_char {
 /// Was marked legacy and removed in issue 6.
 ///
 /// Get an integer from `stream`
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn getw(stream: *mut FILE) -> c_int {
     let mut ret: c_int = 0;
@@ -1125,6 +1128,7 @@ pub unsafe extern "C" fn puts(s: *const c_char) -> c_int {
 /// Marked legacy in SUS Version 2.
 ///
 /// Put an integer `w` into `stream`
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn putw(w: c_int, stream: *mut FILE) -> c_int {
     (unsafe {
@@ -1258,6 +1262,7 @@ pub unsafe extern "C" fn setvbuf(
 /// See <https://pubs.opengroup.org/onlinepubs/009604599/functions/tempnam.html>.
 ///
 /// Marked obsolescent in issue 7.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn tempnam(dir: *const c_char, pfx: *const c_char) -> *mut c_char {
     unsafe fn is_appropriate(pos_dir: *const c_char) -> bool {
@@ -1331,6 +1336,7 @@ pub unsafe extern "C" fn tmpfile() -> *mut FILE {
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/tmpnam.html>.
 ///
 /// Marked obsolescent in issue 7.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn tmpnam(s: *mut c_char) -> *mut c_char {
     let buf = if s.is_null() {
@@ -1343,6 +1349,7 @@ pub unsafe extern "C" fn tmpnam(s: *mut c_char) -> *mut c_char {
     unsafe { tmpnam_inner(buf, 1) }
 }
 
+#[deprecated]
 unsafe extern "C" fn tmpnam_inner(buf: *mut c_char, offset: usize) -> *mut c_char {
     const TEMPLATE: &[u8] = b"XXXXXX\0";
 
diff --git a/src/header/stdlib/mod.rs b/src/header/stdlib/mod.rs
index 2afc7f627c..17132c9c53 100644
--- a/src/header/stdlib/mod.rs
+++ b/src/header/stdlib/mod.rs
@@ -1113,6 +1113,7 @@ pub unsafe extern "C" fn rand() -> c_int {
 /// # Deprecation
 /// The `rand_r()` function was marked as obsolescent in the Open Group Base
 /// Specifications Issue 7, and the function was removed in Issue 8.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn rand_r(seed: *mut c_uint) -> c_int {
     if seed.is_null() {
diff --git a/src/header/sys_time/mod.rs b/src/header/sys_time/mod.rs
index 723ee1a48b..152f145318 100644
--- a/src/header/sys_time/mod.rs
+++ b/src/header/sys_time/mod.rs
@@ -117,6 +117,7 @@ pub unsafe extern "C" fn setitimer(
 /// # Deprecation
 /// The `utimes()` function was marked legacy in the Open Group Base
 /// Specifications Issue 6, and then unmarked in Issue 7.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn utimes(path: *const c_char, times: *const timeval) -> c_int {
     let path = unsafe { CStr::from_ptr(path) };
diff --git a/src/header/sys_timeb/mod.rs b/src/header/sys_timeb/mod.rs
index 85c0ff1ec9..b2294238e5 100644
--- a/src/header/sys_timeb/mod.rs
+++ b/src/header/sys_timeb/mod.rs
@@ -18,6 +18,7 @@ use crate::{
 };
 
 /// See <https://pubs.opengroup.org/onlinepubs/009695399/basedefs/sys/timeb.h.html>.
+#[deprecated]
 #[repr(C)]
 #[derive(Default)]
 pub struct timeb {
@@ -32,6 +33,7 @@ pub struct timeb {
 /// # Safety
 /// The caller must ensure that `tp` is convertible to a `&mut
 /// MaybeUninit<timeb>`.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn ftime(tp: *mut timeb) -> c_int {
     // SAFETY: the caller is required to ensure that the pointer is valid.
diff --git a/src/header/unistd/mod.rs b/src/header/unistd/mod.rs
index 91158a0511..6c00d74964 100644
--- a/src/header/unistd/mod.rs
+++ b/src/header/unistd/mod.rs
@@ -38,7 +38,10 @@ pub use crate::header::pthread::fork_hooks;
 // Inclusion of ctermid() prototype marked as obsolescent since Issue 7, cf.
 // <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/unistd.h.html>.
 // cuserid() marked legacy in Issue 5.
-pub use crate::header::stdio::{ctermid, cuserid};
+#[deprecated]
+pub use crate::header::stdio::ctermid;
+#[allow(deprecated)]
+pub use crate::header::stdio::cuserid;
 
 // TODO: implement and reexport fcntl functions:
 //pub use crate::header::fcntl::{faccessat, fchownat, fexecve, linkat, readlinkat, symlinkat, unlinkat};
diff --git a/src/header/wchar/mod.rs b/src/header/wchar/mod.rs
index b29e71a218..fa4ff454f3 100644
--- a/src/header/wchar/mod.rs
+++ b/src/header/wchar/mod.rs
@@ -911,6 +911,7 @@ pub unsafe extern "C" fn wcstoull(
 ///
 /// Marked legacy in issue 6.
 /// Encouraged to use `wcsstr` instead, which this implementation simply forwards to.
+#[deprecated]
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn wcswcs(ws1: *const wchar_t, ws2: *const wchar_t) -> *mut wchar_t {
     unsafe { wcsstr(ws1, ws2) }