diff --git a/libc-test/build.rs b/libc-test/build.rs
index a31d6ba4878ba..8f7072177c87d 100644
--- a/libc-test/build.rs
+++ b/libc-test/build.rs
@@ -356,9 +356,6 @@ fn test_apple(target: &str) {
             // FIXME(macos): Requires the macOS 14.4 SDK.
             "os_sync_wake_by_address_flags_t" | "os_sync_wait_on_address_flags_t" => true,
 
-            // FIXME(macos): "'__uint128' undeclared" in C
-            "__uint128" => true,
-
             _ => false,
         }
     });
@@ -2037,8 +2034,6 @@ fn test_android(target: &str) {
             "posix_spawn_file_actions_t" => true,
             "posix_spawnattr_t" => true,
 
-            // FIXME(android): "'__uint128' undeclared" in C
-            "__uint128" => true,
             // Added in API level 24
             "if_nameindex" => true,
 
@@ -3413,9 +3408,6 @@ fn test_neutrino(target: &str) {
             // Does not exist in Neutrino
             "locale_t" => true,
 
-            // FIXME: "'__uint128' undeclared" in C
-            "__uint128" => true,
-
             _ => false,
         }
     });
@@ -3955,9 +3947,6 @@ fn test_linux(target: &str) {
             // specific type.
             "Ioctl" => true,
 
-            // FIXME: "'__uint128' undeclared" in C
-            "__uint128" => true,
-
             t => {
                 if musl {
                     // LFS64 types have been removed in musl 1.2.4+
@@ -5525,9 +5514,9 @@ fn test_aix(target: &str) {
     });
 
     cfg.type_name(move |ty, is_struct, is_union| match ty {
-        "DIR"  => ty.to_string(),
-        "FILE"  => ty.to_string(),
-        "ACTION"  => ty.to_string(),
+        "DIR" => ty.to_string(),
+        "FILE" => ty.to_string(),
+        "ACTION" => ty.to_string(),
 
         // 'sigval' is a struct in Rust, but a union in C.
         "sigval" => format!("union sigval"),
@@ -5614,9 +5603,9 @@ fn test_aix(target: &str) {
             // POSIX-compliant versions in the system libc. As a result,
             // function pointer comparisons between the C and Rust sides
             // would fail.
-            "getpwuid_r" | "getpwnam_r" | "getgrgid_r" | "getgrnam_r"
-            | "aio_cancel" | "aio_error" | "aio_fsync" | "aio_read"
-            | "aio_return" | "aio_suspend" | "aio_write" | "select" => true,
+            "getpwuid_r" | "getpwnam_r" | "getgrgid_r" | "getgrnam_r" | "aio_cancel"
+            | "aio_error" | "aio_fsync" | "aio_read" | "aio_return" | "aio_suspend"
+            | "aio_write" | "select" => true,
 
             // 'getdtablesize' is a constant in the AIX header but it is
             // a real function in libc which the Rust side is resolved to.
@@ -5633,7 +5622,6 @@ fn test_aix(target: &str) {
         }
     });
 
-
     cfg.volatile_item(|i| {
         use ctest::VolatileItemKind::*;
         match i {
diff --git a/src/primitives.rs b/src/primitives.rs
index 78b14b52ef1f2..a9821f42c748c 100644
--- a/src/primitives.rs
+++ b/src/primitives.rs
@@ -129,12 +129,16 @@ cfg_if! {
         // [0]: https://github.com/rust-lang/rust/issues/54341
 
         /// C `__int128` (a GCC extension that's part of many ABIs)
+        #[deprecated(since = "0.2.172", note = "Use i128 instead.")]
         pub type __int128 = i128;
         /// C `unsigned __int128` (a GCC extension that's part of many ABIs)
+        #[deprecated(since = "0.2.172", note = "Use u128 instead.")]
         pub type __uint128 = u128;
         /// C __int128_t (alternate name for [__int128][])
+        #[deprecated(since = "0.2.172", note = "Use i128 instead.")]
         pub type __int128_t = i128;
         /// C __uint128_t (alternate name for [__uint128][])
+        #[deprecated(since = "0.2.172", note = "Use u128 instead.")]
         pub type __uint128_t = u128;
 
         // NOTE: if you add more platforms to here, you may need to cfg
@@ -181,8 +185,10 @@ cfg_if! {
         )
     ))] {
         /// C `__int128_t`
+        #[deprecated(since = "0.2.172", note = "Use i128 instead.")]
         pub type __int128_t = i128;
         /// C `__uint128_t`
+        #[deprecated(since = "0.2.172", note = "Use ux128 instead.")]
         pub type __uint128_t = u128;
     }
 }
diff --git a/src/unix/bsd/apple/b64/aarch64/mod.rs b/src/unix/bsd/apple/b64/aarch64/mod.rs
index e300b76ae8228..45bab300eb917 100644
--- a/src/unix/bsd/apple/b64/aarch64/mod.rs
+++ b/src/unix/bsd/apple/b64/aarch64/mod.rs
@@ -40,7 +40,7 @@ s! {
     }
 
     pub struct __darwin_arm_neon_state64 {
-        pub __v: [crate::__uint128_t; 32],
+        pub __v: [u128; 32],
         pub __fpsr: u32,
         pub __fpcr: u32,
     }
diff --git a/src/unix/linux_like/android/b64/aarch64/mod.rs b/src/unix/linux_like/android/b64/aarch64/mod.rs
index b678eb8da6aa4..47d7208b0b9ae 100644
--- a/src/unix/linux_like/android/b64/aarch64/mod.rs
+++ b/src/unix/linux_like/android/b64/aarch64/mod.rs
@@ -78,7 +78,7 @@ s! {
     }
 
     pub struct user_fpsimd_struct {
-        pub vregs: [crate::__uint128_t; 32],
+        pub vregs: [u128; 32],
         pub fpsr: u32,
         pub fpcr: u32,
     }
diff --git a/src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs b/src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs
index 0e990f6006378..f0e64cabfa284 100644
--- a/src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs
+++ b/src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs
@@ -218,7 +218,7 @@ s! {
     }
 
     pub struct user_fpsimd_struct {
-        pub vregs: [crate::__uint128_t; 32],
+        pub vregs: [u128; 32],
         pub fpsr: c_uint,
         pub fpcr: c_uint,
     }
diff --git a/src/unix/linux_like/linux/musl/b64/aarch64/mod.rs b/src/unix/linux_like/linux/musl/b64/aarch64/mod.rs
index 243247edafc46..1addefbb6af24 100644
--- a/src/unix/linux_like/linux/musl/b64/aarch64/mod.rs
+++ b/src/unix/linux_like/linux/musl/b64/aarch64/mod.rs
@@ -122,7 +122,7 @@ s! {
     }
 
     pub struct user_fpsimd_struct {
-        pub vregs: [crate::__uint128_t; 32],
+        pub vregs: [u128; 32],
         pub fpsr: u32,
         pub fpcr: u32,
     }