1 // SPDX-License-Identifier: Apache-2.0 OR MIT 2 3 //! This module provides the macros that actually implement the proc-macros `pin_data` and 4 //! `pinned_drop`. It also contains `__init_internal`, the implementation of the 5 //! `{try_}{pin_}init!` macros. 6 //! 7 //! These macros should never be called directly, since they expect their input to be 8 //! in a certain format which is internal. If used incorrectly, these macros can lead to UB even in 9 //! safe code! Use the public facing macros instead. 10 //! 11 //! This architecture has been chosen because the kernel does not yet have access to `syn` which 12 //! would make matters a lot easier for implementing these as proc-macros. 13 //! 14 //! Since this library and the kernel implementation should diverge as little as possible, the same 15 //! approach has been taken here. 16 //! 17 //! # Macro expansion example 18 //! 19 //! This section is intended for readers trying to understand the macros in this module and the 20 //! `[try_][pin_]init!` macros from `lib.rs`. 21 //! 22 //! We will look at the following example: 23 //! 24 //! ```rust,ignore 25 //! #[pin_data] 26 //! #[repr(C)] 27 //! struct Bar<T> { 28 //! #[pin] 29 //! t: T, 30 //! pub x: usize, 31 //! } 32 //! 33 //! impl<T> Bar<T> { 34 //! fn new(t: T) -> impl PinInit<Self> { 35 //! pin_init!(Self { t, x: 0 }) 36 //! } 37 //! } 38 //! 39 //! #[pin_data(PinnedDrop)] 40 //! struct Foo { 41 //! a: usize, 42 //! #[pin] 43 //! b: Bar<u32>, 44 //! } 45 //! 46 //! #[pinned_drop] 47 //! impl PinnedDrop for Foo { 48 //! fn drop(self: Pin<&mut Self>) { 49 //! println!("{self:p} is getting dropped."); 50 //! } 51 //! } 52 //! 53 //! let a = 42; 54 //! let initializer = pin_init!(Foo { 55 //! a, 56 //! b <- Bar::new(36), 57 //! }); 58 //! ``` 59 //! 60 //! This example includes the most common and important features of the pin-init API. 61 //! 62 //! Below you can find individual section about the different macro invocations. Here are some 63 //! general things we need to take into account when designing macros: 64 //! - use global paths, similarly to file paths, these start with the separator: `::core::panic!()` 65 //! this ensures that the correct item is used, since users could define their own `mod core {}` 66 //! and then their own `panic!` inside to execute arbitrary code inside of our macro. 67 //! - macro `unsafe` hygiene: we need to ensure that we do not expand arbitrary, user-supplied 68 //! expressions inside of an `unsafe` block in the macro, because this would allow users to do 69 //! `unsafe` operations without an associated `unsafe` block. 70 //! 71 //! ## `#[pin_data]` on `Bar` 72 //! 73 //! This macro is used to specify which fields are structurally pinned and which fields are not. It 74 //! is placed on the struct definition and allows `#[pin]` to be placed on the fields. 75 //! 76 //! Here is the definition of `Bar` from our example: 77 //! 78 //! ```rust,ignore 79 //! #[pin_data] 80 //! #[repr(C)] 81 //! struct Bar<T> { 82 //! #[pin] 83 //! t: T, 84 //! pub x: usize, 85 //! } 86 //! ``` 87 //! 88 //! This expands to the following code: 89 //! 90 //! ```rust,ignore 91 //! // Firstly the normal definition of the struct, attributes are preserved: 92 //! #[repr(C)] 93 //! struct Bar<T> { 94 //! t: T, 95 //! pub x: usize, 96 //! } 97 //! // Then an anonymous constant is defined, this is because we do not want any code to access the 98 //! // types that we define inside: 99 //! const _: () = { 100 //! // We define the pin-data carrying struct, it is a ZST and needs to have the same generics, 101 //! // since we need to implement access functions for each field and thus need to know its 102 //! // type. 103 //! struct __ThePinData<T> { 104 //! __phantom: ::core::marker::PhantomData<fn(Bar<T>) -> Bar<T>>, 105 //! } 106 //! // We implement `Copy` for the pin-data struct, since all functions it defines will take 107 //! // `self` by value. 108 //! impl<T> ::core::clone::Clone for __ThePinData<T> { 109 //! fn clone(&self) -> Self { 110 //! *self 111 //! } 112 //! } 113 //! impl<T> ::core::marker::Copy for __ThePinData<T> {} 114 //! // For every field of `Bar`, the pin-data struct will define a function with the same name 115 //! // and accessor (`pub` or `pub(crate)` etc.). This function will take a pointer to the 116 //! // field (`slot`) and a `PinInit` or `Init` depending on the projection kind of the field 117 //! // (if pinning is structural for the field, then `PinInit` otherwise `Init`). 118 //! #[allow(dead_code)] 119 //! impl<T> __ThePinData<T> { 120 //! unsafe fn t<E>( 121 //! self, 122 //! slot: *mut T, 123 //! // Since `t` is `#[pin]`, this is `PinInit`. 124 //! init: impl ::pin_init::PinInit<T, E>, 125 //! ) -> ::core::result::Result<(), E> { 126 //! unsafe { ::pin_init::PinInit::__pinned_init(init, slot) } 127 //! } 128 //! pub unsafe fn x<E>( 129 //! self, 130 //! slot: *mut usize, 131 //! // Since `x` is not `#[pin]`, this is `Init`. 132 //! init: impl ::pin_init::Init<usize, E>, 133 //! ) -> ::core::result::Result<(), E> { 134 //! unsafe { ::pin_init::Init::__init(init, slot) } 135 //! } 136 //! } 137 //! // Implement the internal `HasPinData` trait that associates `Bar` with the pin-data struct 138 //! // that we constructed above. 139 //! unsafe impl<T> ::pin_init::__internal::HasPinData for Bar<T> { 140 //! type PinData = __ThePinData<T>; 141 //! unsafe fn __pin_data() -> Self::PinData { 142 //! __ThePinData { 143 //! __phantom: ::core::marker::PhantomData, 144 //! } 145 //! } 146 //! } 147 //! // Implement the internal `PinData` trait that marks the pin-data struct as a pin-data 148 //! // struct. This is important to ensure that no user can implement a rogue `__pin_data` 149 //! // function without using `unsafe`. 150 //! unsafe impl<T> ::pin_init::__internal::PinData for __ThePinData<T> { 151 //! type Datee = Bar<T>; 152 //! } 153 //! // Now we only want to implement `Unpin` for `Bar` when every structurally pinned field is 154 //! // `Unpin`. In other words, whether `Bar` is `Unpin` only depends on structurally pinned 155 //! // fields (those marked with `#[pin]`). These fields will be listed in this struct, in our 156 //! // case no such fields exist, hence this is almost empty. The two phantomdata fields exist 157 //! // for two reasons: 158 //! // - `__phantom`: every generic must be used, since we cannot really know which generics 159 //! // are used, we declare all and then use everything here once. 160 //! // - `__phantom_pin`: uses the `'__pin` lifetime and ensures that this struct is invariant 161 //! // over it. The lifetime is needed to work around the limitation that trait bounds must 162 //! // not be trivial, e.g. the user has a `#[pin] PhantomPinned` field -- this is 163 //! // unconditionally `!Unpin` and results in an error. The lifetime tricks the compiler 164 //! // into accepting these bounds regardless. 165 //! #[allow(dead_code)] 166 //! struct __Unpin<'__pin, T> { 167 //! __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>, 168 //! __phantom: ::core::marker::PhantomData<fn(Bar<T>) -> Bar<T>>, 169 //! // Our only `#[pin]` field is `t`. 170 //! t: T, 171 //! } 172 //! #[doc(hidden)] 173 //! impl<'__pin, T> ::core::marker::Unpin for Bar<T> 174 //! where 175 //! __Unpin<'__pin, T>: ::core::marker::Unpin, 176 //! {} 177 //! // Now we need to ensure that `Bar` does not implement `Drop`, since that would give users 178 //! // access to `&mut self` inside of `drop` even if the struct was pinned. This could lead to 179 //! // UB with only safe code, so we disallow this by giving a trait implementation error using 180 //! // a direct impl and a blanket implementation. 181 //! trait MustNotImplDrop {} 182 //! // Normally `Drop` bounds do not have the correct semantics, but for this purpose they do 183 //! // (normally people want to know if a type has any kind of drop glue at all, here we want 184 //! // to know if it has any kind of custom drop glue, which is exactly what this bound does). 185 //! #[expect(drop_bounds)] 186 //! impl<T: ::core::ops::Drop> MustNotImplDrop for T {} 187 //! impl<T> MustNotImplDrop for Bar<T> {} 188 //! // Here comes a convenience check, if one implemented `PinnedDrop`, but forgot to add it to 189 //! // `#[pin_data]`, then this will error with the same mechanic as above, this is not needed 190 //! // for safety, but a good sanity check, since no normal code calls `PinnedDrop::drop`. 191 //! #[expect(non_camel_case_types)] 192 //! trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {} 193 //! impl< 194 //! T: ::pin_init::PinnedDrop, 195 //! > UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {} 196 //! impl<T> UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for Bar<T> {} 197 //! }; 198 //! ``` 199 //! 200 //! ## `pin_init!` in `impl Bar` 201 //! 202 //! This macro creates an pin-initializer for the given struct. It requires that the struct is 203 //! annotated by `#[pin_data]`. 204 //! 205 //! Here is the impl on `Bar` defining the new function: 206 //! 207 //! ```rust,ignore 208 //! impl<T> Bar<T> { 209 //! fn new(t: T) -> impl PinInit<Self> { 210 //! pin_init!(Self { t, x: 0 }) 211 //! } 212 //! } 213 //! ``` 214 //! 215 //! This expands to the following code: 216 //! 217 //! ```rust,ignore 218 //! impl<T> Bar<T> { 219 //! fn new(t: T) -> impl PinInit<Self> { 220 //! { 221 //! // We do not want to allow arbitrary returns, so we declare this type as the `Ok` 222 //! // return type and shadow it later when we insert the arbitrary user code. That way 223 //! // there will be no possibility of returning without `unsafe`. 224 //! struct __InitOk; 225 //! // Get the data about fields from the supplied type. 226 //! // - the function is unsafe, hence the unsafe block 227 //! // - we `use` the `HasPinData` trait in the block, it is only available in that 228 //! // scope. 229 //! let data = unsafe { 230 //! use ::pin_init::__internal::HasPinData; 231 //! Self::__pin_data() 232 //! }; 233 //! // Ensure that `data` really is of type `PinData` and help with type inference: 234 //! let init = ::pin_init::__internal::PinData::make_closure::< 235 //! _, 236 //! __InitOk, 237 //! ::core::convert::Infallible, 238 //! >(data, move |slot| { 239 //! { 240 //! // Shadow the structure so it cannot be used to return early. If a user 241 //! // tries to write `return Ok(__InitOk)`, then they get a type error, 242 //! // since that will refer to this struct instead of the one defined 243 //! // above. 244 //! struct __InitOk; 245 //! // This is the expansion of `t,`, which is syntactic sugar for `t: t,`. 246 //! { 247 //! unsafe { ::core::ptr::write(::core::addr_of_mut!((*slot).t), t) }; 248 //! } 249 //! // Since initialization could fail later (not in this case, since the 250 //! // error type is `Infallible`) we will need to drop this field if there 251 //! // is an error later. This `DropGuard` will drop the field when it gets 252 //! // dropped and has not yet been forgotten. 253 //! let __t_guard = unsafe { 254 //! ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).t)) 255 //! }; 256 //! // Expansion of `x: 0,`: 257 //! // Since this can be an arbitrary expression we cannot place it inside 258 //! // of the `unsafe` block, so we bind it here. 259 //! { 260 //! let x = 0; 261 //! unsafe { ::core::ptr::write(::core::addr_of_mut!((*slot).x), x) }; 262 //! } 263 //! // We again create a `DropGuard`. 264 //! let __x_guard = unsafe { 265 //! ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).x)) 266 //! }; 267 //! // Since initialization has successfully completed, we can now forget 268 //! // the guards. This is not `mem::forget`, since we only have 269 //! // `&DropGuard`. 270 //! ::core::mem::forget(__x_guard); 271 //! ::core::mem::forget(__t_guard); 272 //! // Here we use the type checker to ensure that every field has been 273 //! // initialized exactly once, since this is `if false` it will never get 274 //! // executed, but still type-checked. 275 //! // Additionally we abuse `slot` to automatically infer the correct type 276 //! // for the struct. This is also another check that every field is 277 //! // accessible from this scope. 278 //! #[allow(unreachable_code, clippy::diverging_sub_expression)] 279 //! let _ = || { 280 //! unsafe { 281 //! ::core::ptr::write( 282 //! slot, 283 //! Self { 284 //! // We only care about typecheck finding every field 285 //! // here, the expression does not matter, just conjure 286 //! // one using `panic!()`: 287 //! t: ::core::panic!(), 288 //! x: ::core::panic!(), 289 //! }, 290 //! ); 291 //! }; 292 //! }; 293 //! } 294 //! // We leave the scope above and gain access to the previously shadowed 295 //! // `__InitOk` that we need to return. 296 //! Ok(__InitOk) 297 //! }); 298 //! // Change the return type from `__InitOk` to `()`. 299 //! let init = move | 300 //! slot, 301 //! | -> ::core::result::Result<(), ::core::convert::Infallible> { 302 //! init(slot).map(|__InitOk| ()) 303 //! }; 304 //! // Construct the initializer. 305 //! let init = unsafe { 306 //! ::pin_init::pin_init_from_closure::< 307 //! _, 308 //! ::core::convert::Infallible, 309 //! >(init) 310 //! }; 311 //! init 312 //! } 313 //! } 314 //! } 315 //! ``` 316 //! 317 //! ## `#[pin_data]` on `Foo` 318 //! 319 //! Since we already took a look at `#[pin_data]` on `Bar`, this section will only explain the 320 //! differences/new things in the expansion of the `Foo` definition: 321 //! 322 //! ```rust,ignore 323 //! #[pin_data(PinnedDrop)] 324 //! struct Foo { 325 //! a: usize, 326 //! #[pin] 327 //! b: Bar<u32>, 328 //! } 329 //! ``` 330 //! 331 //! This expands to the following code: 332 //! 333 //! ```rust,ignore 334 //! struct Foo { 335 //! a: usize, 336 //! b: Bar<u32>, 337 //! } 338 //! const _: () = { 339 //! struct __ThePinData { 340 //! __phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>, 341 //! } 342 //! impl ::core::clone::Clone for __ThePinData { 343 //! fn clone(&self) -> Self { 344 //! *self 345 //! } 346 //! } 347 //! impl ::core::marker::Copy for __ThePinData {} 348 //! #[allow(dead_code)] 349 //! impl __ThePinData { 350 //! unsafe fn b<E>( 351 //! self, 352 //! slot: *mut Bar<u32>, 353 //! init: impl ::pin_init::PinInit<Bar<u32>, E>, 354 //! ) -> ::core::result::Result<(), E> { 355 //! unsafe { ::pin_init::PinInit::__pinned_init(init, slot) } 356 //! } 357 //! unsafe fn a<E>( 358 //! self, 359 //! slot: *mut usize, 360 //! init: impl ::pin_init::Init<usize, E>, 361 //! ) -> ::core::result::Result<(), E> { 362 //! unsafe { ::pin_init::Init::__init(init, slot) } 363 //! } 364 //! } 365 //! unsafe impl ::pin_init::__internal::HasPinData for Foo { 366 //! type PinData = __ThePinData; 367 //! unsafe fn __pin_data() -> Self::PinData { 368 //! __ThePinData { 369 //! __phantom: ::core::marker::PhantomData, 370 //! } 371 //! } 372 //! } 373 //! unsafe impl ::pin_init::__internal::PinData for __ThePinData { 374 //! type Datee = Foo; 375 //! } 376 //! #[allow(dead_code)] 377 //! struct __Unpin<'__pin> { 378 //! __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>, 379 //! __phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>, 380 //! b: Bar<u32>, 381 //! } 382 //! #[doc(hidden)] 383 //! impl<'__pin> ::core::marker::Unpin for Foo 384 //! where 385 //! __Unpin<'__pin>: ::core::marker::Unpin, 386 //! {} 387 //! // Since we specified `PinnedDrop` as the argument to `#[pin_data]`, we expect `Foo` to 388 //! // implement `PinnedDrop`. Thus we do not need to prevent `Drop` implementations like 389 //! // before, instead we implement `Drop` here and delegate to `PinnedDrop`. 390 //! impl ::core::ops::Drop for Foo { 391 //! fn drop(&mut self) { 392 //! // Since we are getting dropped, no one else has a reference to `self` and thus we 393 //! // can assume that we never move. 394 //! let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) }; 395 //! // Create the unsafe token that proves that we are inside of a destructor, this 396 //! // type is only allowed to be created in a destructor. 397 //! let token = unsafe { ::pin_init::__internal::OnlyCallFromDrop::new() }; 398 //! ::pin_init::PinnedDrop::drop(pinned, token); 399 //! } 400 //! } 401 //! }; 402 //! ``` 403 //! 404 //! ## `#[pinned_drop]` on `impl PinnedDrop for Foo` 405 //! 406 //! This macro is used to implement the `PinnedDrop` trait, since that trait is `unsafe` and has an 407 //! extra parameter that should not be used at all. The macro hides that parameter. 408 //! 409 //! Here is the `PinnedDrop` impl for `Foo`: 410 //! 411 //! ```rust,ignore 412 //! #[pinned_drop] 413 //! impl PinnedDrop for Foo { 414 //! fn drop(self: Pin<&mut Self>) { 415 //! println!("{self:p} is getting dropped."); 416 //! } 417 //! } 418 //! ``` 419 //! 420 //! This expands to the following code: 421 //! 422 //! ```rust,ignore 423 //! // `unsafe`, full path and the token parameter are added, everything else stays the same. 424 //! unsafe impl ::pin_init::PinnedDrop for Foo { 425 //! fn drop(self: Pin<&mut Self>, _: ::pin_init::__internal::OnlyCallFromDrop) { 426 //! println!("{self:p} is getting dropped."); 427 //! } 428 //! } 429 //! ``` 430 //! 431 //! ## `pin_init!` on `Foo` 432 //! 433 //! Since we already took a look at `pin_init!` on `Bar`, this section will only show the expansion 434 //! of `pin_init!` on `Foo`: 435 //! 436 //! ```rust,ignore 437 //! let a = 42; 438 //! let initializer = pin_init!(Foo { 439 //! a, 440 //! b <- Bar::new(36), 441 //! }); 442 //! ``` 443 //! 444 //! This expands to the following code: 445 //! 446 //! ```rust,ignore 447 //! let a = 42; 448 //! let initializer = { 449 //! struct __InitOk; 450 //! let data = unsafe { 451 //! use ::pin_init::__internal::HasPinData; 452 //! Foo::__pin_data() 453 //! }; 454 //! let init = ::pin_init::__internal::PinData::make_closure::< 455 //! _, 456 //! __InitOk, 457 //! ::core::convert::Infallible, 458 //! >(data, move |slot| { 459 //! { 460 //! struct __InitOk; 461 //! { 462 //! unsafe { ::core::ptr::write(::core::addr_of_mut!((*slot).a), a) }; 463 //! } 464 //! let __a_guard = unsafe { 465 //! ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).a)) 466 //! }; 467 //! let init = Bar::new(36); 468 //! unsafe { data.b(::core::addr_of_mut!((*slot).b), b)? }; 469 //! let __b_guard = unsafe { 470 //! ::pin_init::__internal::DropGuard::new(::core::addr_of_mut!((*slot).b)) 471 //! }; 472 //! ::core::mem::forget(__b_guard); 473 //! ::core::mem::forget(__a_guard); 474 //! #[allow(unreachable_code, clippy::diverging_sub_expression)] 475 //! let _ = || { 476 //! unsafe { 477 //! ::core::ptr::write( 478 //! slot, 479 //! Foo { 480 //! a: ::core::panic!(), 481 //! b: ::core::panic!(), 482 //! }, 483 //! ); 484 //! }; 485 //! }; 486 //! } 487 //! Ok(__InitOk) 488 //! }); 489 //! let init = move | 490 //! slot, 491 //! | -> ::core::result::Result<(), ::core::convert::Infallible> { 492 //! init(slot).map(|__InitOk| ()) 493 //! }; 494 //! let init = unsafe { 495 //! ::pin_init::pin_init_from_closure::<_, ::core::convert::Infallible>(init) 496 //! }; 497 //! init 498 //! }; 499 //! ``` 500 501 #[cfg(kernel)] 502 pub use ::macros::paste; 503 #[cfg(not(kernel))] 504 pub use ::paste::paste; 505 506 /// Creates a `unsafe impl<...> PinnedDrop for $type` block. 507 /// 508 /// See [`PinnedDrop`] for more information. 509 #[doc(hidden)] 510 #[macro_export] 511 macro_rules! __pinned_drop { 512 ( 513 @impl_sig($($impl_sig:tt)*), 514 @impl_body( 515 $(#[$($attr:tt)*])* 516 fn drop($($sig:tt)*) { 517 $($inner:tt)* 518 } 519 ), 520 ) => { 521 // SAFETY: TODO. 522 unsafe $($impl_sig)* { 523 // Inherit all attributes and the type/ident tokens for the signature. 524 $(#[$($attr)*])* 525 fn drop($($sig)*, _: $crate::__internal::OnlyCallFromDrop) { 526 $($inner)* 527 } 528 } 529 } 530 } 531 532 /// This macro first parses the struct definition such that it separates pinned and not pinned 533 /// fields. Afterwards it declares the struct and implement the `PinData` trait safely. 534 #[doc(hidden)] 535 #[macro_export] 536 macro_rules! __pin_data { 537 // Proc-macro entry point, this is supplied by the proc-macro pre-parsing. 538 (parse_input: 539 @args($($pinned_drop:ident)?), 540 @sig( 541 $(#[$($struct_attr:tt)*])* 542 $vis:vis struct $name:ident 543 $(where $($whr:tt)*)? 544 ), 545 @impl_generics($($impl_generics:tt)*), 546 @ty_generics($($ty_generics:tt)*), 547 @decl_generics($($decl_generics:tt)*), 548 @body({ $($fields:tt)* }), 549 ) => { 550 // We now use token munching to iterate through all of the fields. While doing this we 551 // identify fields marked with `#[pin]`, these fields are the 'pinned fields'. The user 552 // wants these to be structurally pinned. The rest of the fields are the 553 // 'not pinned fields'. Additionally we collect all fields, since we need them in the right 554 // order to declare the struct. 555 // 556 // In this call we also put some explaining comments for the parameters. 557 $crate::__pin_data!(find_pinned_fields: 558 // Attributes on the struct itself, these will just be propagated to be put onto the 559 // struct definition. 560 @struct_attrs($(#[$($struct_attr)*])*), 561 // The visibility of the struct. 562 @vis($vis), 563 // The name of the struct. 564 @name($name), 565 // The 'impl generics', the generics that will need to be specified on the struct inside 566 // of an `impl<$ty_generics>` block. 567 @impl_generics($($impl_generics)*), 568 // The 'ty generics', the generics that will need to be specified on the impl blocks. 569 @ty_generics($($ty_generics)*), 570 // The 'decl generics', the generics that need to be specified on the struct 571 // definition. 572 @decl_generics($($decl_generics)*), 573 // The where clause of any impl block and the declaration. 574 @where($($($whr)*)?), 575 // The remaining fields tokens that need to be processed. 576 // We add a `,` at the end to ensure correct parsing. 577 @fields_munch($($fields)* ,), 578 // The pinned fields. 579 @pinned(), 580 // The not pinned fields. 581 @not_pinned(), 582 // All fields. 583 @fields(), 584 // The accumulator containing all attributes already parsed. 585 @accum(), 586 // Contains `yes` or `` to indicate if `#[pin]` was found on the current field. 587 @is_pinned(), 588 // The proc-macro argument, this should be `PinnedDrop` or ``. 589 @pinned_drop($($pinned_drop)?), 590 ); 591 }; 592 (find_pinned_fields: 593 @struct_attrs($($struct_attrs:tt)*), 594 @vis($vis:vis), 595 @name($name:ident), 596 @impl_generics($($impl_generics:tt)*), 597 @ty_generics($($ty_generics:tt)*), 598 @decl_generics($($decl_generics:tt)*), 599 @where($($whr:tt)*), 600 // We found a PhantomPinned field, this should generally be pinned! 601 @fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*), 602 @pinned($($pinned:tt)*), 603 @not_pinned($($not_pinned:tt)*), 604 @fields($($fields:tt)*), 605 @accum($($accum:tt)*), 606 // This field is not pinned. 607 @is_pinned(), 608 @pinned_drop($($pinned_drop:ident)?), 609 ) => { 610 ::core::compile_error!(concat!( 611 "The field `", 612 stringify!($field), 613 "` of type `PhantomPinned` only has an effect, if it has the `#[pin]` attribute.", 614 )); 615 $crate::__pin_data!(find_pinned_fields: 616 @struct_attrs($($struct_attrs)*), 617 @vis($vis), 618 @name($name), 619 @impl_generics($($impl_generics)*), 620 @ty_generics($($ty_generics)*), 621 @decl_generics($($decl_generics)*), 622 @where($($whr)*), 623 @fields_munch($($rest)*), 624 @pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,), 625 @not_pinned($($not_pinned)*), 626 @fields($($fields)* $($accum)* $field: ::core::marker::PhantomPinned,), 627 @accum(), 628 @is_pinned(), 629 @pinned_drop($($pinned_drop)?), 630 ); 631 }; 632 (find_pinned_fields: 633 @struct_attrs($($struct_attrs:tt)*), 634 @vis($vis:vis), 635 @name($name:ident), 636 @impl_generics($($impl_generics:tt)*), 637 @ty_generics($($ty_generics:tt)*), 638 @decl_generics($($decl_generics:tt)*), 639 @where($($whr:tt)*), 640 // We reached the field declaration. 641 @fields_munch($field:ident : $type:ty, $($rest:tt)*), 642 @pinned($($pinned:tt)*), 643 @not_pinned($($not_pinned:tt)*), 644 @fields($($fields:tt)*), 645 @accum($($accum:tt)*), 646 // This field is pinned. 647 @is_pinned(yes), 648 @pinned_drop($($pinned_drop:ident)?), 649 ) => { 650 $crate::__pin_data!(find_pinned_fields: 651 @struct_attrs($($struct_attrs)*), 652 @vis($vis), 653 @name($name), 654 @impl_generics($($impl_generics)*), 655 @ty_generics($($ty_generics)*), 656 @decl_generics($($decl_generics)*), 657 @where($($whr)*), 658 @fields_munch($($rest)*), 659 @pinned($($pinned)* $($accum)* $field: $type,), 660 @not_pinned($($not_pinned)*), 661 @fields($($fields)* $($accum)* $field: $type,), 662 @accum(), 663 @is_pinned(), 664 @pinned_drop($($pinned_drop)?), 665 ); 666 }; 667 (find_pinned_fields: 668 @struct_attrs($($struct_attrs:tt)*), 669 @vis($vis:vis), 670 @name($name:ident), 671 @impl_generics($($impl_generics:tt)*), 672 @ty_generics($($ty_generics:tt)*), 673 @decl_generics($($decl_generics:tt)*), 674 @where($($whr:tt)*), 675 // We reached the field declaration. 676 @fields_munch($field:ident : $type:ty, $($rest:tt)*), 677 @pinned($($pinned:tt)*), 678 @not_pinned($($not_pinned:tt)*), 679 @fields($($fields:tt)*), 680 @accum($($accum:tt)*), 681 // This field is not pinned. 682 @is_pinned(), 683 @pinned_drop($($pinned_drop:ident)?), 684 ) => { 685 $crate::__pin_data!(find_pinned_fields: 686 @struct_attrs($($struct_attrs)*), 687 @vis($vis), 688 @name($name), 689 @impl_generics($($impl_generics)*), 690 @ty_generics($($ty_generics)*), 691 @decl_generics($($decl_generics)*), 692 @where($($whr)*), 693 @fields_munch($($rest)*), 694 @pinned($($pinned)*), 695 @not_pinned($($not_pinned)* $($accum)* $field: $type,), 696 @fields($($fields)* $($accum)* $field: $type,), 697 @accum(), 698 @is_pinned(), 699 @pinned_drop($($pinned_drop)?), 700 ); 701 }; 702 (find_pinned_fields: 703 @struct_attrs($($struct_attrs:tt)*), 704 @vis($vis:vis), 705 @name($name:ident), 706 @impl_generics($($impl_generics:tt)*), 707 @ty_generics($($ty_generics:tt)*), 708 @decl_generics($($decl_generics:tt)*), 709 @where($($whr:tt)*), 710 // We found the `#[pin]` attr. 711 @fields_munch(#[pin] $($rest:tt)*), 712 @pinned($($pinned:tt)*), 713 @not_pinned($($not_pinned:tt)*), 714 @fields($($fields:tt)*), 715 @accum($($accum:tt)*), 716 @is_pinned($($is_pinned:ident)?), 717 @pinned_drop($($pinned_drop:ident)?), 718 ) => { 719 $crate::__pin_data!(find_pinned_fields: 720 @struct_attrs($($struct_attrs)*), 721 @vis($vis), 722 @name($name), 723 @impl_generics($($impl_generics)*), 724 @ty_generics($($ty_generics)*), 725 @decl_generics($($decl_generics)*), 726 @where($($whr)*), 727 @fields_munch($($rest)*), 728 // We do not include `#[pin]` in the list of attributes, since it is not actually an 729 // attribute that is defined somewhere. 730 @pinned($($pinned)*), 731 @not_pinned($($not_pinned)*), 732 @fields($($fields)*), 733 @accum($($accum)*), 734 // Set this to `yes`. 735 @is_pinned(yes), 736 @pinned_drop($($pinned_drop)?), 737 ); 738 }; 739 (find_pinned_fields: 740 @struct_attrs($($struct_attrs:tt)*), 741 @vis($vis:vis), 742 @name($name:ident), 743 @impl_generics($($impl_generics:tt)*), 744 @ty_generics($($ty_generics:tt)*), 745 @decl_generics($($decl_generics:tt)*), 746 @where($($whr:tt)*), 747 // We reached the field declaration with visibility, for simplicity we only munch the 748 // visibility and put it into `$accum`. 749 @fields_munch($fvis:vis $field:ident $($rest:tt)*), 750 @pinned($($pinned:tt)*), 751 @not_pinned($($not_pinned:tt)*), 752 @fields($($fields:tt)*), 753 @accum($($accum:tt)*), 754 @is_pinned($($is_pinned:ident)?), 755 @pinned_drop($($pinned_drop:ident)?), 756 ) => { 757 $crate::__pin_data!(find_pinned_fields: 758 @struct_attrs($($struct_attrs)*), 759 @vis($vis), 760 @name($name), 761 @impl_generics($($impl_generics)*), 762 @ty_generics($($ty_generics)*), 763 @decl_generics($($decl_generics)*), 764 @where($($whr)*), 765 @fields_munch($field $($rest)*), 766 @pinned($($pinned)*), 767 @not_pinned($($not_pinned)*), 768 @fields($($fields)*), 769 @accum($($accum)* $fvis), 770 @is_pinned($($is_pinned)?), 771 @pinned_drop($($pinned_drop)?), 772 ); 773 }; 774 (find_pinned_fields: 775 @struct_attrs($($struct_attrs:tt)*), 776 @vis($vis:vis), 777 @name($name:ident), 778 @impl_generics($($impl_generics:tt)*), 779 @ty_generics($($ty_generics:tt)*), 780 @decl_generics($($decl_generics:tt)*), 781 @where($($whr:tt)*), 782 // Some other attribute, just put it into `$accum`. 783 @fields_munch(#[$($attr:tt)*] $($rest:tt)*), 784 @pinned($($pinned:tt)*), 785 @not_pinned($($not_pinned:tt)*), 786 @fields($($fields:tt)*), 787 @accum($($accum:tt)*), 788 @is_pinned($($is_pinned:ident)?), 789 @pinned_drop($($pinned_drop:ident)?), 790 ) => { 791 $crate::__pin_data!(find_pinned_fields: 792 @struct_attrs($($struct_attrs)*), 793 @vis($vis), 794 @name($name), 795 @impl_generics($($impl_generics)*), 796 @ty_generics($($ty_generics)*), 797 @decl_generics($($decl_generics)*), 798 @where($($whr)*), 799 @fields_munch($($rest)*), 800 @pinned($($pinned)*), 801 @not_pinned($($not_pinned)*), 802 @fields($($fields)*), 803 @accum($($accum)* #[$($attr)*]), 804 @is_pinned($($is_pinned)?), 805 @pinned_drop($($pinned_drop)?), 806 ); 807 }; 808 (find_pinned_fields: 809 @struct_attrs($($struct_attrs:tt)*), 810 @vis($vis:vis), 811 @name($name:ident), 812 @impl_generics($($impl_generics:tt)*), 813 @ty_generics($($ty_generics:tt)*), 814 @decl_generics($($decl_generics:tt)*), 815 @where($($whr:tt)*), 816 // We reached the end of the fields, plus an optional additional comma, since we added one 817 // before and the user is also allowed to put a trailing comma. 818 @fields_munch($(,)?), 819 @pinned($($pinned:tt)*), 820 @not_pinned($($not_pinned:tt)*), 821 @fields($($fields:tt)*), 822 @accum(), 823 @is_pinned(), 824 @pinned_drop($($pinned_drop:ident)?), 825 ) => { 826 // Declare the struct with all fields in the correct order. 827 $($struct_attrs)* 828 $vis struct $name <$($decl_generics)*> 829 where $($whr)* 830 { 831 $($fields)* 832 } 833 834 // We put the rest into this const item, because it then will not be accessible to anything 835 // outside. 836 const _: () = { 837 // We declare this struct which will host all of the projection function for our type. 838 // it will be invariant over all generic parameters which are inherited from the 839 // struct. 840 $vis struct __ThePinData<$($impl_generics)*> 841 where $($whr)* 842 { 843 __phantom: ::core::marker::PhantomData< 844 fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> 845 >, 846 } 847 848 impl<$($impl_generics)*> ::core::clone::Clone for __ThePinData<$($ty_generics)*> 849 where $($whr)* 850 { 851 fn clone(&self) -> Self { *self } 852 } 853 854 impl<$($impl_generics)*> ::core::marker::Copy for __ThePinData<$($ty_generics)*> 855 where $($whr)* 856 {} 857 858 // Make all projection functions. 859 $crate::__pin_data!(make_pin_data: 860 @pin_data(__ThePinData), 861 @impl_generics($($impl_generics)*), 862 @ty_generics($($ty_generics)*), 863 @where($($whr)*), 864 @pinned($($pinned)*), 865 @not_pinned($($not_pinned)*), 866 ); 867 868 // SAFETY: We have added the correct projection functions above to `__ThePinData` and 869 // we also use the least restrictive generics possible. 870 unsafe impl<$($impl_generics)*> 871 $crate::__internal::HasPinData for $name<$($ty_generics)*> 872 where $($whr)* 873 { 874 type PinData = __ThePinData<$($ty_generics)*>; 875 876 unsafe fn __pin_data() -> Self::PinData { 877 __ThePinData { __phantom: ::core::marker::PhantomData } 878 } 879 } 880 881 // SAFETY: TODO. 882 unsafe impl<$($impl_generics)*> 883 $crate::__internal::PinData for __ThePinData<$($ty_generics)*> 884 where $($whr)* 885 { 886 type Datee = $name<$($ty_generics)*>; 887 } 888 889 // This struct will be used for the unpin analysis. Since only structurally pinned 890 // fields are relevant whether the struct should implement `Unpin`. 891 #[allow(dead_code)] 892 struct __Unpin <'__pin, $($impl_generics)*> 893 where $($whr)* 894 { 895 __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>, 896 __phantom: ::core::marker::PhantomData< 897 fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> 898 >, 899 // Only the pinned fields. 900 $($pinned)* 901 } 902 903 #[doc(hidden)] 904 impl<'__pin, $($impl_generics)*> ::core::marker::Unpin for $name<$($ty_generics)*> 905 where 906 __Unpin<'__pin, $($ty_generics)*>: ::core::marker::Unpin, 907 $($whr)* 908 {} 909 910 // We need to disallow normal `Drop` implementation, the exact behavior depends on 911 // whether `PinnedDrop` was specified as the parameter. 912 $crate::__pin_data!(drop_prevention: 913 @name($name), 914 @impl_generics($($impl_generics)*), 915 @ty_generics($($ty_generics)*), 916 @where($($whr)*), 917 @pinned_drop($($pinned_drop)?), 918 ); 919 }; 920 }; 921 // When no `PinnedDrop` was specified, then we have to prevent implementing drop. 922 (drop_prevention: 923 @name($name:ident), 924 @impl_generics($($impl_generics:tt)*), 925 @ty_generics($($ty_generics:tt)*), 926 @where($($whr:tt)*), 927 @pinned_drop(), 928 ) => { 929 // We prevent this by creating a trait that will be implemented for all types implementing 930 // `Drop`. Additionally we will implement this trait for the struct leading to a conflict, 931 // if it also implements `Drop` 932 trait MustNotImplDrop {} 933 #[expect(drop_bounds)] 934 impl<T: ::core::ops::Drop> MustNotImplDrop for T {} 935 impl<$($impl_generics)*> MustNotImplDrop for $name<$($ty_generics)*> 936 where $($whr)* {} 937 // We also take care to prevent users from writing a useless `PinnedDrop` implementation. 938 // They might implement `PinnedDrop` correctly for the struct, but forget to give 939 // `PinnedDrop` as the parameter to `#[pin_data]`. 940 #[expect(non_camel_case_types)] 941 trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {} 942 impl<T: $crate::PinnedDrop> 943 UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {} 944 impl<$($impl_generics)*> 945 UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for $name<$($ty_generics)*> 946 where $($whr)* {} 947 }; 948 // When `PinnedDrop` was specified we just implement `Drop` and delegate. 949 (drop_prevention: 950 @name($name:ident), 951 @impl_generics($($impl_generics:tt)*), 952 @ty_generics($($ty_generics:tt)*), 953 @where($($whr:tt)*), 954 @pinned_drop(PinnedDrop), 955 ) => { 956 impl<$($impl_generics)*> ::core::ops::Drop for $name<$($ty_generics)*> 957 where $($whr)* 958 { 959 fn drop(&mut self) { 960 // SAFETY: Since this is a destructor, `self` will not move after this function 961 // terminates, since it is inaccessible. 962 let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) }; 963 // SAFETY: Since this is a drop function, we can create this token to call the 964 // pinned destructor of this type. 965 let token = unsafe { $crate::__internal::OnlyCallFromDrop::new() }; 966 $crate::PinnedDrop::drop(pinned, token); 967 } 968 } 969 }; 970 // If some other parameter was specified, we emit a readable error. 971 (drop_prevention: 972 @name($name:ident), 973 @impl_generics($($impl_generics:tt)*), 974 @ty_generics($($ty_generics:tt)*), 975 @where($($whr:tt)*), 976 @pinned_drop($($rest:tt)*), 977 ) => { 978 compile_error!( 979 "Wrong parameters to `#[pin_data]`, expected nothing or `PinnedDrop`, got '{}'.", 980 stringify!($($rest)*), 981 ); 982 }; 983 (make_pin_data: 984 @pin_data($pin_data:ident), 985 @impl_generics($($impl_generics:tt)*), 986 @ty_generics($($ty_generics:tt)*), 987 @where($($whr:tt)*), 988 @pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?), 989 @not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?), 990 ) => { 991 // For every field, we create a projection function according to its projection type. If a 992 // field is structurally pinned, then it must be initialized via `PinInit`, if it is not 993 // structurally pinned, then it can be initialized via `Init`. 994 // 995 // The functions are `unsafe` to prevent accidentally calling them. 996 #[allow(dead_code)] 997 #[expect(clippy::missing_safety_doc)] 998 impl<$($impl_generics)*> $pin_data<$($ty_generics)*> 999 where $($whr)* 1000 { 1001 $( 1002 $(#[$($p_attr)*])* 1003 $pvis unsafe fn $p_field<E>( 1004 self, 1005 slot: *mut $p_type, 1006 init: impl $crate::PinInit<$p_type, E>, 1007 ) -> ::core::result::Result<(), E> { 1008 // SAFETY: TODO. 1009 unsafe { $crate::PinInit::__pinned_init(init, slot) } 1010 } 1011 )* 1012 $( 1013 $(#[$($attr)*])* 1014 $fvis unsafe fn $field<E>( 1015 self, 1016 slot: *mut $type, 1017 init: impl $crate::Init<$type, E>, 1018 ) -> ::core::result::Result<(), E> { 1019 // SAFETY: TODO. 1020 unsafe { $crate::Init::__init(init, slot) } 1021 } 1022 )* 1023 } 1024 }; 1025 } 1026 1027 /// The internal init macro. Do not call manually! 1028 /// 1029 /// This is called by the `{try_}{pin_}init!` macros with various inputs. 1030 /// 1031 /// This macro has multiple internal call configurations, these are always the very first ident: 1032 /// - nothing: this is the base case and called by the `{try_}{pin_}init!` macros. 1033 /// - `with_update_parsed`: when the `..Zeroable::zeroed()` syntax has been handled. 1034 /// - `init_slot`: recursively creates the code that initializes all fields in `slot`. 1035 /// - `make_initializer`: recursively create the struct initializer that guarantees that every 1036 /// field has been initialized exactly once. 1037 #[doc(hidden)] 1038 #[macro_export] 1039 macro_rules! __init_internal { 1040 ( 1041 @this($($this:ident)?), 1042 @typ($t:path), 1043 @fields($($fields:tt)*), 1044 @error($err:ty), 1045 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1046 // case. 1047 @data($data:ident, $($use_data:ident)?), 1048 // `HasPinData` or `HasInitData`. 1049 @has_data($has_data:ident, $get_data:ident), 1050 // `pin_init_from_closure` or `init_from_closure`. 1051 @construct_closure($construct_closure:ident), 1052 @munch_fields(), 1053 ) => { 1054 $crate::__init_internal!(with_update_parsed: 1055 @this($($this)?), 1056 @typ($t), 1057 @fields($($fields)*), 1058 @error($err), 1059 @data($data, $($use_data)?), 1060 @has_data($has_data, $get_data), 1061 @construct_closure($construct_closure), 1062 @zeroed(), // Nothing means default behavior. 1063 ) 1064 }; 1065 ( 1066 @this($($this:ident)?), 1067 @typ($t:path), 1068 @fields($($fields:tt)*), 1069 @error($err:ty), 1070 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1071 // case. 1072 @data($data:ident, $($use_data:ident)?), 1073 // `HasPinData` or `HasInitData`. 1074 @has_data($has_data:ident, $get_data:ident), 1075 // `pin_init_from_closure` or `init_from_closure`. 1076 @construct_closure($construct_closure:ident), 1077 @munch_fields(..Zeroable::zeroed()), 1078 ) => { 1079 $crate::__init_internal!(with_update_parsed: 1080 @this($($this)?), 1081 @typ($t), 1082 @fields($($fields)*), 1083 @error($err), 1084 @data($data, $($use_data)?), 1085 @has_data($has_data, $get_data), 1086 @construct_closure($construct_closure), 1087 @zeroed(()), // `()` means zero all fields not mentioned. 1088 ) 1089 }; 1090 ( 1091 @this($($this:ident)?), 1092 @typ($t:path), 1093 @fields($($fields:tt)*), 1094 @error($err:ty), 1095 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1096 // case. 1097 @data($data:ident, $($use_data:ident)?), 1098 // `HasPinData` or `HasInitData`. 1099 @has_data($has_data:ident, $get_data:ident), 1100 // `pin_init_from_closure` or `init_from_closure`. 1101 @construct_closure($construct_closure:ident), 1102 @munch_fields($ignore:tt $($rest:tt)*), 1103 ) => { 1104 $crate::__init_internal!( 1105 @this($($this)?), 1106 @typ($t), 1107 @fields($($fields)*), 1108 @error($err), 1109 @data($data, $($use_data)?), 1110 @has_data($has_data, $get_data), 1111 @construct_closure($construct_closure), 1112 @munch_fields($($rest)*), 1113 ) 1114 }; 1115 (with_update_parsed: 1116 @this($($this:ident)?), 1117 @typ($t:path), 1118 @fields($($fields:tt)*), 1119 @error($err:ty), 1120 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1121 // case. 1122 @data($data:ident, $($use_data:ident)?), 1123 // `HasPinData` or `HasInitData`. 1124 @has_data($has_data:ident, $get_data:ident), 1125 // `pin_init_from_closure` or `init_from_closure`. 1126 @construct_closure($construct_closure:ident), 1127 @zeroed($($init_zeroed:expr)?), 1128 ) => {{ 1129 // We do not want to allow arbitrary returns, so we declare this type as the `Ok` return 1130 // type and shadow it later when we insert the arbitrary user code. That way there will be 1131 // no possibility of returning without `unsafe`. 1132 struct __InitOk; 1133 // Get the data about fields from the supplied type. 1134 // 1135 // SAFETY: TODO. 1136 let data = unsafe { 1137 use $crate::__internal::$has_data; 1138 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1139 // information that is associated to already parsed fragments, so a path fragment 1140 // cannot be used in this position. Doing the retokenization results in valid rust 1141 // code. 1142 $crate::macros::paste!($t::$get_data()) 1143 }; 1144 // Ensure that `data` really is of type `$data` and help with type inference: 1145 let init = $crate::__internal::$data::make_closure::<_, __InitOk, $err>( 1146 data, 1147 move |slot| { 1148 { 1149 // Shadow the structure so it cannot be used to return early. 1150 struct __InitOk; 1151 // If `$init_zeroed` is present we should zero the slot now and not emit an 1152 // error when fields are missing (since they will be zeroed). We also have to 1153 // check that the type actually implements `Zeroable`. 1154 $({ 1155 fn assert_zeroable<T: $crate::Zeroable>(_: *mut T) {} 1156 // Ensure that the struct is indeed `Zeroable`. 1157 assert_zeroable(slot); 1158 // SAFETY: The type implements `Zeroable` by the check above. 1159 unsafe { ::core::ptr::write_bytes(slot, 0, 1) }; 1160 $init_zeroed // This will be `()` if set. 1161 })? 1162 // Create the `this` so it can be referenced by the user inside of the 1163 // expressions creating the individual fields. 1164 $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? 1165 // Initialize every field. 1166 $crate::__init_internal!(init_slot($($use_data)?): 1167 @data(data), 1168 @slot(slot), 1169 @guards(), 1170 @munch_fields($($fields)*,), 1171 ); 1172 // We use unreachable code to ensure that all fields have been mentioned exactly 1173 // once, this struct initializer will still be type-checked and complain with a 1174 // very natural error message if a field is forgotten/mentioned more than once. 1175 #[allow(unreachable_code, clippy::diverging_sub_expression)] 1176 let _ = || { 1177 $crate::__init_internal!(make_initializer: 1178 @slot(slot), 1179 @type_name($t), 1180 @munch_fields($($fields)*,), 1181 @acc(), 1182 ); 1183 }; 1184 } 1185 Ok(__InitOk) 1186 } 1187 ); 1188 let init = move |slot| -> ::core::result::Result<(), $err> { 1189 init(slot).map(|__InitOk| ()) 1190 }; 1191 // SAFETY: TODO. 1192 let init = unsafe { $crate::$construct_closure::<_, $err>(init) }; 1193 init 1194 }}; 1195 (init_slot($($use_data:ident)?): 1196 @data($data:ident), 1197 @slot($slot:ident), 1198 @guards($($guards:ident,)*), 1199 @munch_fields($(..Zeroable::zeroed())? $(,)?), 1200 ) => { 1201 // Endpoint of munching, no fields are left. If execution reaches this point, all fields 1202 // have been initialized. Therefore we can now dismiss the guards by forgetting them. 1203 $(::core::mem::forget($guards);)* 1204 }; 1205 (init_slot($use_data:ident): // `use_data` is present, so we use the `data` to init fields. 1206 @data($data:ident), 1207 @slot($slot:ident), 1208 @guards($($guards:ident,)*), 1209 // In-place initialization syntax. 1210 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1211 ) => { 1212 let init = $val; 1213 // Call the initializer. 1214 // 1215 // SAFETY: `slot` is valid, because we are inside of an initializer closure, we 1216 // return when an error/panic occurs. 1217 // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`. 1218 unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? }; 1219 // Create the drop guard: 1220 // 1221 // We rely on macro hygiene to make it impossible for users to access this local variable. 1222 // We use `paste!` to create new hygiene for `$field`. 1223 $crate::macros::paste! { 1224 // SAFETY: We forget the guard later when initialization has succeeded. 1225 let [< __ $field _guard >] = unsafe { 1226 $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1227 }; 1228 1229 $crate::__init_internal!(init_slot($use_data): 1230 @data($data), 1231 @slot($slot), 1232 @guards([< __ $field _guard >], $($guards,)*), 1233 @munch_fields($($rest)*), 1234 ); 1235 } 1236 }; 1237 (init_slot(): // No `use_data`, so we use `Init::__init` directly. 1238 @data($data:ident), 1239 @slot($slot:ident), 1240 @guards($($guards:ident,)*), 1241 // In-place initialization syntax. 1242 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1243 ) => { 1244 let init = $val; 1245 // Call the initializer. 1246 // 1247 // SAFETY: `slot` is valid, because we are inside of an initializer closure, we 1248 // return when an error/panic occurs. 1249 unsafe { $crate::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? }; 1250 // Create the drop guard: 1251 // 1252 // We rely on macro hygiene to make it impossible for users to access this local variable. 1253 // We use `paste!` to create new hygiene for `$field`. 1254 $crate::macros::paste! { 1255 // SAFETY: We forget the guard later when initialization has succeeded. 1256 let [< __ $field _guard >] = unsafe { 1257 $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1258 }; 1259 1260 $crate::__init_internal!(init_slot(): 1261 @data($data), 1262 @slot($slot), 1263 @guards([< __ $field _guard >], $($guards,)*), 1264 @munch_fields($($rest)*), 1265 ); 1266 } 1267 }; 1268 (init_slot($($use_data:ident)?): 1269 @data($data:ident), 1270 @slot($slot:ident), 1271 @guards($($guards:ident,)*), 1272 // Init by-value. 1273 @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), 1274 ) => { 1275 { 1276 $(let $field = $val;)? 1277 // Initialize the field. 1278 // 1279 // SAFETY: The memory at `slot` is uninitialized. 1280 unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; 1281 } 1282 // Create the drop guard: 1283 // 1284 // We rely on macro hygiene to make it impossible for users to access this local variable. 1285 // We use `paste!` to create new hygiene for `$field`. 1286 $crate::macros::paste! { 1287 // SAFETY: We forget the guard later when initialization has succeeded. 1288 let [< __ $field _guard >] = unsafe { 1289 $crate::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1290 }; 1291 1292 $crate::__init_internal!(init_slot($($use_data)?): 1293 @data($data), 1294 @slot($slot), 1295 @guards([< __ $field _guard >], $($guards,)*), 1296 @munch_fields($($rest)*), 1297 ); 1298 } 1299 }; 1300 (make_initializer: 1301 @slot($slot:ident), 1302 @type_name($t:path), 1303 @munch_fields(..Zeroable::zeroed() $(,)?), 1304 @acc($($acc:tt)*), 1305 ) => { 1306 // Endpoint, nothing more to munch, create the initializer. Since the users specified 1307 // `..Zeroable::zeroed()`, the slot will already have been zeroed and all field that have 1308 // not been overwritten are thus zero and initialized. We still check that all fields are 1309 // actually accessible by using the struct update syntax ourselves. 1310 // We are inside of a closure that is never executed and thus we can abuse `slot` to 1311 // get the correct type inference here: 1312 #[allow(unused_assignments)] 1313 unsafe { 1314 let mut zeroed = ::core::mem::zeroed(); 1315 // We have to use type inference here to make zeroed have the correct type. This does 1316 // not get executed, so it has no effect. 1317 ::core::ptr::write($slot, zeroed); 1318 zeroed = ::core::mem::zeroed(); 1319 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1320 // information that is associated to already parsed fragments, so a path fragment 1321 // cannot be used in this position. Doing the retokenization results in valid rust 1322 // code. 1323 $crate::macros::paste!( 1324 ::core::ptr::write($slot, $t { 1325 $($acc)* 1326 ..zeroed 1327 }); 1328 ); 1329 } 1330 }; 1331 (make_initializer: 1332 @slot($slot:ident), 1333 @type_name($t:path), 1334 @munch_fields($(,)?), 1335 @acc($($acc:tt)*), 1336 ) => { 1337 // Endpoint, nothing more to munch, create the initializer. 1338 // Since we are in the closure that is never called, this will never get executed. 1339 // We abuse `slot` to get the correct type inference here: 1340 // 1341 // SAFETY: TODO. 1342 unsafe { 1343 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1344 // information that is associated to already parsed fragments, so a path fragment 1345 // cannot be used in this position. Doing the retokenization results in valid rust 1346 // code. 1347 $crate::macros::paste!( 1348 ::core::ptr::write($slot, $t { 1349 $($acc)* 1350 }); 1351 ); 1352 } 1353 }; 1354 (make_initializer: 1355 @slot($slot:ident), 1356 @type_name($t:path), 1357 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1358 @acc($($acc:tt)*), 1359 ) => { 1360 $crate::__init_internal!(make_initializer: 1361 @slot($slot), 1362 @type_name($t), 1363 @munch_fields($($rest)*), 1364 @acc($($acc)* $field: ::core::panic!(),), 1365 ); 1366 }; 1367 (make_initializer: 1368 @slot($slot:ident), 1369 @type_name($t:path), 1370 @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), 1371 @acc($($acc:tt)*), 1372 ) => { 1373 $crate::__init_internal!(make_initializer: 1374 @slot($slot), 1375 @type_name($t), 1376 @munch_fields($($rest)*), 1377 @acc($($acc)* $field: ::core::panic!(),), 1378 ); 1379 }; 1380 } 1381 1382 #[doc(hidden)] 1383 #[macro_export] 1384 macro_rules! __derive_zeroable { 1385 (parse_input: 1386 @sig( 1387 $(#[$($struct_attr:tt)*])* 1388 $vis:vis struct $name:ident 1389 $(where $($whr:tt)*)? 1390 ), 1391 @impl_generics($($impl_generics:tt)*), 1392 @ty_generics($($ty_generics:tt)*), 1393 @body({ 1394 $( 1395 $(#[$($field_attr:tt)*])* 1396 $field_vis:vis $field:ident : $field_ty:ty 1397 ),* $(,)? 1398 }), 1399 ) => { 1400 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. 1401 #[automatically_derived] 1402 unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> 1403 where 1404 $($($whr)*)? 1405 {} 1406 const _: () = { 1407 fn assert_zeroable<T: ?::core::marker::Sized + $crate::Zeroable>() {} 1408 fn ensure_zeroable<$($impl_generics)*>() 1409 where $($($whr)*)? 1410 { 1411 $(assert_zeroable::<$field_ty>();)* 1412 } 1413 }; 1414 }; 1415 (parse_input: 1416 @sig( 1417 $(#[$($struct_attr:tt)*])* 1418 $vis:vis union $name:ident 1419 $(where $($whr:tt)*)? 1420 ), 1421 @impl_generics($($impl_generics:tt)*), 1422 @ty_generics($($ty_generics:tt)*), 1423 @body({ 1424 $( 1425 $(#[$($field_attr:tt)*])* 1426 $field_vis:vis $field:ident : $field_ty:ty 1427 ),* $(,)? 1428 }), 1429 ) => { 1430 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. 1431 #[automatically_derived] 1432 unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> 1433 where 1434 $($($whr)*)? 1435 {} 1436 const _: () = { 1437 fn assert_zeroable<T: ?::core::marker::Sized + $crate::Zeroable>() {} 1438 fn ensure_zeroable<$($impl_generics)*>() 1439 where $($($whr)*)? 1440 { 1441 $(assert_zeroable::<$field_ty>();)* 1442 } 1443 }; 1444 }; 1445 } 1446 1447 #[doc(hidden)] 1448 #[macro_export] 1449 macro_rules! __maybe_derive_zeroable { 1450 (parse_input: 1451 @sig( 1452 $(#[$($struct_attr:tt)*])* 1453 $vis:vis struct $name:ident 1454 $(where $($whr:tt)*)? 1455 ), 1456 @impl_generics($($impl_generics:tt)*), 1457 @ty_generics($($ty_generics:tt)*), 1458 @body({ 1459 $( 1460 $(#[$($field_attr:tt)*])* 1461 $field_vis:vis $field:ident : $field_ty:ty 1462 ),* $(,)? 1463 }), 1464 ) => { 1465 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. 1466 #[automatically_derived] 1467 unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> 1468 where 1469 $( 1470 // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds` 1471 // feature <https://github.com/rust-lang/rust/issues/48214#issuecomment-2557829956>. 1472 $field_ty: for<'__dummy> $crate::Zeroable, 1473 )* 1474 $($($whr)*)? 1475 {} 1476 }; 1477 (parse_input: 1478 @sig( 1479 $(#[$($struct_attr:tt)*])* 1480 $vis:vis union $name:ident 1481 $(where $($whr:tt)*)? 1482 ), 1483 @impl_generics($($impl_generics:tt)*), 1484 @ty_generics($($ty_generics:tt)*), 1485 @body({ 1486 $( 1487 $(#[$($field_attr:tt)*])* 1488 $field_vis:vis $field:ident : $field_ty:ty 1489 ),* $(,)? 1490 }), 1491 ) => { 1492 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. 1493 #[automatically_derived] 1494 unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> 1495 where 1496 $( 1497 // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds` 1498 // feature <https://github.com/rust-lang/rust/issues/48214#issuecomment-2557829956>. 1499 $field_ty: for<'__dummy> $crate::Zeroable, 1500 )* 1501 $($($whr)*)? 1502 {} 1503 }; 1504 } 1505