core: Add core::ffi::c_intptr_t and core::ffi::c_uintptr_t

Tracking issue: #88345

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>

Author: lygstate

compiler/rustc_feature/src/unstable.rs

@@ -422,6 +422,8 @@ declare_features! (
     (unstable, avx10_target_feature, "1.88.0", Some(138843)),
     /// Target features on bpf.
     (unstable, bpf_target_feature, "1.54.0", Some(150247)),
+    /// Allows using size_t/ssize_t/uintptr_t/intptr_t/ptrdiff_t.
+    (unstable, c_size_t, "CURRENT_RUSTC_VERSION", Some(88345)),
     /// Allows using C-variadics.
     (unstable, c_variadic, "1.34.0", Some(44930)),
     /// Allows defining c-variadic functions on targets where this feature has not yet

compiler/rustc_span/src/symbol.rs

@@ -545,6 +545,7 @@ symbols! {
         builtin_syntax,
         bundle,
         c_dash_variadic,
+        c_size_t,
         c_str_literals,
         c_unwind,
         c_variadic,

library/core/src/ffi/mod.rs

@@ -38,7 +38,7 @@ pub use self::primitives::{
     c_ulong, c_ulonglong, c_ushort,
 };
 #[unstable(feature = "c_size_t", issue = "88345")]
-pub use self::primitives::{c_ptrdiff_t, c_size_t, c_ssize_t};
+pub use self::primitives::{c_intptr_t, c_ptrdiff_t, c_size_t, c_ssize_t, c_uintptr_t};
 
 // N.B., for LLVM to recognize the void pointer type and by extension
 //     functions like malloc(), we need to have it represented as i8* in

library/core/src/ffi/primitives.rs

@@ -174,6 +174,26 @@ pub type c_ptrdiff_t = isize;
 #[unstable(feature = "c_size_t", issue = "88345")]
 pub type c_ssize_t = isize;
 
+/// Equivalent to C's `intptr_t` type.
+///
+/// This type have the same size with a pointer. The C standard technically only
+/// requires that this type be a signed integer type just capable of holding a
+/// pointer.
+#[unstable(feature = "c_size_t", issue = "88345")]
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct c_intptr_t(*const ());
+
+/// Equivalent to C's `uintptr_t` type.
+///
+/// This type have the same size with a pointer. The C standard technically only
+/// requires that this type be an unsigned integer type just capable of holding
+/// a pointer.
+#[unstable(feature = "c_size_t", issue = "88345")]
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct c_uintptr_t(*const ());
+
 mod c_int_definition {
     crate::cfg_select! {
         any(target_arch = "avr", target_arch = "msp430") => {

library/coretests/tests/ffi.rs

@@ -1 +1,2 @@
 mod cstr;
+mod intptr;

library/coretests/tests/ffi/intptr.rs

@@ -0,0 +1,17 @@
+#![deny(fuzzy_provenance_casts)]
+#![deny(lossy_provenance_casts)]
+
+use core::ffi::{c_intptr_t, c_uintptr_t};
+
+#[test]
+fn test_intptr_unitptr() {
+    // These types should have the same size as a pointer.
+    assert_eq!(core::mem::size_of::<c_intptr_t>(), core::mem::size_of::<*const ()>());
+    assert_eq!(core::mem::size_of::<c_uintptr_t>(), core::mem::size_of::<*const ()>());
+
+    let ptr = NonNull::with_exposed_provenance(16_usize);
+    let ptr_uintptr_t = ptr as c_uintptr_t;
+    let ptr_back = ptr_uintptr_t as *const ();
+    assert_eq!(ptr_back.addr(), 16_usize);
+    assert_eq!(ptr, ptr_back);
+}

library/coretests/tests/lib.rs

@@ -11,6 +11,7 @@
 #![feature(bool_to_result)]
 #![feature(borrowed_buf_init)]
 #![feature(bstr)]
+#![feature(c_size_t)]
 #![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(char_internals)]
 #![feature(clone_to_uninit)]

library/std/src/ffi/mod.rs

@@ -179,7 +179,7 @@ pub use core::ffi::{
     c_ulong, c_ulonglong, c_ushort,
 };
 #[unstable(feature = "c_size_t", issue = "88345")]
-pub use core::ffi::{c_ptrdiff_t, c_size_t, c_ssize_t};
+pub use core::ffi::{c_intptr_t, c_ptrdiff_t, c_size_t, c_ssize_t, c_uintptr_t};
 
 #[doc(inline)]
 #[stable(feature = "cstr_from_bytes_until_nul", since = "1.69.0")]

src/doc/unstable-book/src/language-features/c-size-t.md

@@ -0,0 +1,20 @@
+# `c_size_t`
+
+The tracking issue for this feature is: [#88345]
+
+[#88345]: https://github.com/rust-lang/rust/issues/88345
+-----
+
+The `c_size_t` feature allows to enable C FFI types `size_t` `ssize_t` `intptr_t` `uintptr_t` `ptrdiff_t`.
+
+## Example
+
+```rust
+#![feature(c_size_t)]
+
+use std::ffi::{c_intptr_t, c_ptrdiff_t, c_size_t, c_ssize_t, c_uintptr_t};
+
+fn main() {
+    let _ptr_integer = 16_usize as c_uintptr_t;
+}
+```

tests/ui/feature-gates/feature-gate-c-size-t.rs

@@ -0,0 +1,4 @@
+#![crate_type = "lib"]
+
+use std::ffi::{c_intptr_t};
+//~^ ERROR use of unstable library feature `c_size_t`