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 `{try_}{pin_}init!` 5 //! 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 //! # Macro expansion example 15 //! 16 //! This section is intended for readers trying to understand the macros in this module and the 17 //! `pin_init!` macros from `init.rs`. 18 //! 19 //! We will look at the following example: 20 //! 21 //! ```rust,ignore 22 //! # use kernel::init::*; 23 //! # use core::pin::Pin; 24 //! #[pin_data] 25 //! #[repr(C)] 26 //! struct Bar<T> { 27 //! #[pin] 28 //! t: T, 29 //! pub x: usize, 30 //! } 31 //! 32 //! impl<T> Bar<T> { 33 //! fn new(t: T) -> impl PinInit<Self> { 34 //! pin_init!(Self { t, x: 0 }) 35 //! } 36 //! } 37 //! 38 //! #[pin_data(PinnedDrop)] 39 //! struct Foo { 40 //! a: usize, 41 //! #[pin] 42 //! b: Bar<u32>, 43 //! } 44 //! 45 //! #[pinned_drop] 46 //! impl PinnedDrop for Foo { 47 //! fn drop(self: Pin<&mut Self>) { 48 //! pr_info!("{self:p} is getting dropped."); 49 //! } 50 //! } 51 //! 52 //! let a = 42; 53 //! let initializer = pin_init!(Foo { 54 //! a, 55 //! b <- Bar::new(36), 56 //! }); 57 //! ``` 58 //! 59 //! This example includes the most common and important features of the pin-init API. 60 //! 61 //! Below you can find individual section about the different macro invocations. Here are some 62 //! general things we need to take into account when designing macros: 63 //! - use global paths, similarly to file paths, these start with the separator: `::core::panic!()` 64 //! this ensures that the correct item is used, since users could define their own `mod core {}` 65 //! and then their own `panic!` inside to execute arbitrary code inside of our macro. 66 //! - macro `unsafe` hygiene: we need to ensure that we do not expand arbitrary, user-supplied 67 //! expressions inside of an `unsafe` block in the macro, because this would allow users to do 68 //! `unsafe` operations without an associated `unsafe` block. 69 //! 70 //! ## `#[pin_data]` on `Bar` 71 //! 72 //! This macro is used to specify which fields are structurally pinned and which fields are not. It 73 //! is placed on the struct definition and allows `#[pin]` to be placed on the fields. 74 //! 75 //! Here is the definition of `Bar` from our example: 76 //! 77 //! ```rust,ignore 78 //! # use kernel::init::*; 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 ::kernel::init::PinInit<T, E>, 125 //! ) -> ::core::result::Result<(), E> { 126 //! unsafe { ::kernel::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 ::kernel::init::Init<usize, E>, 133 //! ) -> ::core::result::Result<(), E> { 134 //! unsafe { ::kernel::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> ::kernel::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> ::kernel::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: ::kernel::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 ::kernel::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 = ::kernel::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 //! ::pinned_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 //! ::kernel::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 //! ::kernel::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 ::kernel::init::PinInit<Bar<u32>, E>, 354 //! ) -> ::core::result::Result<(), E> { 355 //! unsafe { ::kernel::init::PinInit::__pinned_init(init, slot) } 356 //! } 357 //! unsafe fn a<E>( 358 //! self, 359 //! slot: *mut usize, 360 //! init: impl ::kernel::init::Init<usize, E>, 361 //! ) -> ::core::result::Result<(), E> { 362 //! unsafe { ::kernel::init::Init::__init(init, slot) } 363 //! } 364 //! } 365 //! unsafe impl ::kernel::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 ::kernel::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 { ::kernel::init::__internal::OnlyCallFromDrop::new() }; 398 //! ::kernel::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 //! pr_info!("{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 ::kernel::init::PinnedDrop for Foo { 425 //! fn drop(self: Pin<&mut Self>, _: ::kernel::init::__internal::OnlyCallFromDrop) { 426 //! pr_info!("{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 ::kernel::init::__internal::HasPinData; 452 //! Foo::__pin_data() 453 //! }; 454 //! let init = ::kernel::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 //! ::kernel::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 //! ::kernel::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 //! ::kernel::init::pin_init_from_closure::<_, ::core::convert::Infallible>(init) 496 //! }; 497 //! init 498 //! }; 499 //! ``` 500 501 pub use ::macros::paste; 502 503 /// Creates a `unsafe impl<...> PinnedDrop for $type` block. 504 /// 505 /// See [`PinnedDrop`] for more information. 506 #[doc(hidden)] 507 #[macro_export] 508 macro_rules! __pinned_drop { 509 ( 510 @impl_sig($($impl_sig:tt)*), 511 @impl_body( 512 $(#[$($attr:tt)*])* 513 fn drop($($sig:tt)*) { 514 $($inner:tt)* 515 } 516 ), 517 ) => { 518 // SAFETY: TODO. 519 unsafe $($impl_sig)* { 520 // Inherit all attributes and the type/ident tokens for the signature. 521 $(#[$($attr)*])* 522 fn drop($($sig)*, _: $crate::init::__internal::OnlyCallFromDrop) { 523 $($inner)* 524 } 525 } 526 } 527 } 528 529 /// This macro first parses the struct definition such that it separates pinned and not pinned 530 /// fields. Afterwards it declares the struct and implement the `PinData` trait safely. 531 #[doc(hidden)] 532 #[macro_export] 533 macro_rules! __pin_data { 534 // Proc-macro entry point, this is supplied by the proc-macro pre-parsing. 535 (parse_input: 536 @args($($pinned_drop:ident)?), 537 @sig( 538 $(#[$($struct_attr:tt)*])* 539 $vis:vis struct $name:ident 540 $(where $($whr:tt)*)? 541 ), 542 @impl_generics($($impl_generics:tt)*), 543 @ty_generics($($ty_generics:tt)*), 544 @decl_generics($($decl_generics:tt)*), 545 @body({ $($fields:tt)* }), 546 ) => { 547 // We now use token munching to iterate through all of the fields. While doing this we 548 // identify fields marked with `#[pin]`, these fields are the 'pinned fields'. The user 549 // wants these to be structurally pinned. The rest of the fields are the 550 // 'not pinned fields'. Additionally we collect all fields, since we need them in the right 551 // order to declare the struct. 552 // 553 // In this call we also put some explaining comments for the parameters. 554 $crate::__pin_data!(find_pinned_fields: 555 // Attributes on the struct itself, these will just be propagated to be put onto the 556 // struct definition. 557 @struct_attrs($(#[$($struct_attr)*])*), 558 // The visibility of the struct. 559 @vis($vis), 560 // The name of the struct. 561 @name($name), 562 // The 'impl generics', the generics that will need to be specified on the struct inside 563 // of an `impl<$ty_generics>` block. 564 @impl_generics($($impl_generics)*), 565 // The 'ty generics', the generics that will need to be specified on the impl blocks. 566 @ty_generics($($ty_generics)*), 567 // The 'decl generics', the generics that need to be specified on the struct 568 // definition. 569 @decl_generics($($decl_generics)*), 570 // The where clause of any impl block and the declaration. 571 @where($($($whr)*)?), 572 // The remaining fields tokens that need to be processed. 573 // We add a `,` at the end to ensure correct parsing. 574 @fields_munch($($fields)* ,), 575 // The pinned fields. 576 @pinned(), 577 // The not pinned fields. 578 @not_pinned(), 579 // All fields. 580 @fields(), 581 // The accumulator containing all attributes already parsed. 582 @accum(), 583 // Contains `yes` or `` to indicate if `#[pin]` was found on the current field. 584 @is_pinned(), 585 // The proc-macro argument, this should be `PinnedDrop` or ``. 586 @pinned_drop($($pinned_drop)?), 587 ); 588 }; 589 (find_pinned_fields: 590 @struct_attrs($($struct_attrs:tt)*), 591 @vis($vis:vis), 592 @name($name:ident), 593 @impl_generics($($impl_generics:tt)*), 594 @ty_generics($($ty_generics:tt)*), 595 @decl_generics($($decl_generics:tt)*), 596 @where($($whr:tt)*), 597 // We found a PhantomPinned field, this should generally be pinned! 598 @fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*), 599 @pinned($($pinned:tt)*), 600 @not_pinned($($not_pinned:tt)*), 601 @fields($($fields:tt)*), 602 @accum($($accum:tt)*), 603 // This field is not pinned. 604 @is_pinned(), 605 @pinned_drop($($pinned_drop:ident)?), 606 ) => { 607 ::core::compile_error!(concat!( 608 "The field `", 609 stringify!($field), 610 "` of type `PhantomPinned` only has an effect, if it has the `#[pin]` attribute.", 611 )); 612 $crate::__pin_data!(find_pinned_fields: 613 @struct_attrs($($struct_attrs)*), 614 @vis($vis), 615 @name($name), 616 @impl_generics($($impl_generics)*), 617 @ty_generics($($ty_generics)*), 618 @decl_generics($($decl_generics)*), 619 @where($($whr)*), 620 @fields_munch($($rest)*), 621 @pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,), 622 @not_pinned($($not_pinned)*), 623 @fields($($fields)* $($accum)* $field: ::core::marker::PhantomPinned,), 624 @accum(), 625 @is_pinned(), 626 @pinned_drop($($pinned_drop)?), 627 ); 628 }; 629 (find_pinned_fields: 630 @struct_attrs($($struct_attrs:tt)*), 631 @vis($vis:vis), 632 @name($name:ident), 633 @impl_generics($($impl_generics:tt)*), 634 @ty_generics($($ty_generics:tt)*), 635 @decl_generics($($decl_generics:tt)*), 636 @where($($whr:tt)*), 637 // We reached the field declaration. 638 @fields_munch($field:ident : $type:ty, $($rest:tt)*), 639 @pinned($($pinned:tt)*), 640 @not_pinned($($not_pinned:tt)*), 641 @fields($($fields:tt)*), 642 @accum($($accum:tt)*), 643 // This field is pinned. 644 @is_pinned(yes), 645 @pinned_drop($($pinned_drop:ident)?), 646 ) => { 647 $crate::__pin_data!(find_pinned_fields: 648 @struct_attrs($($struct_attrs)*), 649 @vis($vis), 650 @name($name), 651 @impl_generics($($impl_generics)*), 652 @ty_generics($($ty_generics)*), 653 @decl_generics($($decl_generics)*), 654 @where($($whr)*), 655 @fields_munch($($rest)*), 656 @pinned($($pinned)* $($accum)* $field: $type,), 657 @not_pinned($($not_pinned)*), 658 @fields($($fields)* $($accum)* $field: $type,), 659 @accum(), 660 @is_pinned(), 661 @pinned_drop($($pinned_drop)?), 662 ); 663 }; 664 (find_pinned_fields: 665 @struct_attrs($($struct_attrs:tt)*), 666 @vis($vis:vis), 667 @name($name:ident), 668 @impl_generics($($impl_generics:tt)*), 669 @ty_generics($($ty_generics:tt)*), 670 @decl_generics($($decl_generics:tt)*), 671 @where($($whr:tt)*), 672 // We reached the field declaration. 673 @fields_munch($field:ident : $type:ty, $($rest:tt)*), 674 @pinned($($pinned:tt)*), 675 @not_pinned($($not_pinned:tt)*), 676 @fields($($fields:tt)*), 677 @accum($($accum:tt)*), 678 // This field is not pinned. 679 @is_pinned(), 680 @pinned_drop($($pinned_drop:ident)?), 681 ) => { 682 $crate::__pin_data!(find_pinned_fields: 683 @struct_attrs($($struct_attrs)*), 684 @vis($vis), 685 @name($name), 686 @impl_generics($($impl_generics)*), 687 @ty_generics($($ty_generics)*), 688 @decl_generics($($decl_generics)*), 689 @where($($whr)*), 690 @fields_munch($($rest)*), 691 @pinned($($pinned)*), 692 @not_pinned($($not_pinned)* $($accum)* $field: $type,), 693 @fields($($fields)* $($accum)* $field: $type,), 694 @accum(), 695 @is_pinned(), 696 @pinned_drop($($pinned_drop)?), 697 ); 698 }; 699 (find_pinned_fields: 700 @struct_attrs($($struct_attrs:tt)*), 701 @vis($vis:vis), 702 @name($name:ident), 703 @impl_generics($($impl_generics:tt)*), 704 @ty_generics($($ty_generics:tt)*), 705 @decl_generics($($decl_generics:tt)*), 706 @where($($whr:tt)*), 707 // We found the `#[pin]` attr. 708 @fields_munch(#[pin] $($rest:tt)*), 709 @pinned($($pinned:tt)*), 710 @not_pinned($($not_pinned:tt)*), 711 @fields($($fields:tt)*), 712 @accum($($accum:tt)*), 713 @is_pinned($($is_pinned:ident)?), 714 @pinned_drop($($pinned_drop:ident)?), 715 ) => { 716 $crate::__pin_data!(find_pinned_fields: 717 @struct_attrs($($struct_attrs)*), 718 @vis($vis), 719 @name($name), 720 @impl_generics($($impl_generics)*), 721 @ty_generics($($ty_generics)*), 722 @decl_generics($($decl_generics)*), 723 @where($($whr)*), 724 @fields_munch($($rest)*), 725 // We do not include `#[pin]` in the list of attributes, since it is not actually an 726 // attribute that is defined somewhere. 727 @pinned($($pinned)*), 728 @not_pinned($($not_pinned)*), 729 @fields($($fields)*), 730 @accum($($accum)*), 731 // Set this to `yes`. 732 @is_pinned(yes), 733 @pinned_drop($($pinned_drop)?), 734 ); 735 }; 736 (find_pinned_fields: 737 @struct_attrs($($struct_attrs:tt)*), 738 @vis($vis:vis), 739 @name($name:ident), 740 @impl_generics($($impl_generics:tt)*), 741 @ty_generics($($ty_generics:tt)*), 742 @decl_generics($($decl_generics:tt)*), 743 @where($($whr:tt)*), 744 // We reached the field declaration with visibility, for simplicity we only munch the 745 // visibility and put it into `$accum`. 746 @fields_munch($fvis:vis $field:ident $($rest:tt)*), 747 @pinned($($pinned:tt)*), 748 @not_pinned($($not_pinned:tt)*), 749 @fields($($fields:tt)*), 750 @accum($($accum:tt)*), 751 @is_pinned($($is_pinned:ident)?), 752 @pinned_drop($($pinned_drop:ident)?), 753 ) => { 754 $crate::__pin_data!(find_pinned_fields: 755 @struct_attrs($($struct_attrs)*), 756 @vis($vis), 757 @name($name), 758 @impl_generics($($impl_generics)*), 759 @ty_generics($($ty_generics)*), 760 @decl_generics($($decl_generics)*), 761 @where($($whr)*), 762 @fields_munch($field $($rest)*), 763 @pinned($($pinned)*), 764 @not_pinned($($not_pinned)*), 765 @fields($($fields)*), 766 @accum($($accum)* $fvis), 767 @is_pinned($($is_pinned)?), 768 @pinned_drop($($pinned_drop)?), 769 ); 770 }; 771 (find_pinned_fields: 772 @struct_attrs($($struct_attrs:tt)*), 773 @vis($vis:vis), 774 @name($name:ident), 775 @impl_generics($($impl_generics:tt)*), 776 @ty_generics($($ty_generics:tt)*), 777 @decl_generics($($decl_generics:tt)*), 778 @where($($whr:tt)*), 779 // Some other attribute, just put it into `$accum`. 780 @fields_munch(#[$($attr:tt)*] $($rest:tt)*), 781 @pinned($($pinned:tt)*), 782 @not_pinned($($not_pinned:tt)*), 783 @fields($($fields:tt)*), 784 @accum($($accum:tt)*), 785 @is_pinned($($is_pinned:ident)?), 786 @pinned_drop($($pinned_drop:ident)?), 787 ) => { 788 $crate::__pin_data!(find_pinned_fields: 789 @struct_attrs($($struct_attrs)*), 790 @vis($vis), 791 @name($name), 792 @impl_generics($($impl_generics)*), 793 @ty_generics($($ty_generics)*), 794 @decl_generics($($decl_generics)*), 795 @where($($whr)*), 796 @fields_munch($($rest)*), 797 @pinned($($pinned)*), 798 @not_pinned($($not_pinned)*), 799 @fields($($fields)*), 800 @accum($($accum)* #[$($attr)*]), 801 @is_pinned($($is_pinned)?), 802 @pinned_drop($($pinned_drop)?), 803 ); 804 }; 805 (find_pinned_fields: 806 @struct_attrs($($struct_attrs:tt)*), 807 @vis($vis:vis), 808 @name($name:ident), 809 @impl_generics($($impl_generics:tt)*), 810 @ty_generics($($ty_generics:tt)*), 811 @decl_generics($($decl_generics:tt)*), 812 @where($($whr:tt)*), 813 // We reached the end of the fields, plus an optional additional comma, since we added one 814 // before and the user is also allowed to put a trailing comma. 815 @fields_munch($(,)?), 816 @pinned($($pinned:tt)*), 817 @not_pinned($($not_pinned:tt)*), 818 @fields($($fields:tt)*), 819 @accum(), 820 @is_pinned(), 821 @pinned_drop($($pinned_drop:ident)?), 822 ) => { 823 // Declare the struct with all fields in the correct order. 824 $($struct_attrs)* 825 $vis struct $name <$($decl_generics)*> 826 where $($whr)* 827 { 828 $($fields)* 829 } 830 831 // We put the rest into this const item, because it then will not be accessible to anything 832 // outside. 833 const _: () = { 834 // We declare this struct which will host all of the projection function for our type. 835 // it will be invariant over all generic parameters which are inherited from the 836 // struct. 837 $vis struct __ThePinData<$($impl_generics)*> 838 where $($whr)* 839 { 840 __phantom: ::core::marker::PhantomData< 841 fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> 842 >, 843 } 844 845 impl<$($impl_generics)*> ::core::clone::Clone for __ThePinData<$($ty_generics)*> 846 where $($whr)* 847 { 848 fn clone(&self) -> Self { *self } 849 } 850 851 impl<$($impl_generics)*> ::core::marker::Copy for __ThePinData<$($ty_generics)*> 852 where $($whr)* 853 {} 854 855 // Make all projection functions. 856 $crate::__pin_data!(make_pin_data: 857 @pin_data(__ThePinData), 858 @impl_generics($($impl_generics)*), 859 @ty_generics($($ty_generics)*), 860 @where($($whr)*), 861 @pinned($($pinned)*), 862 @not_pinned($($not_pinned)*), 863 ); 864 865 // SAFETY: We have added the correct projection functions above to `__ThePinData` and 866 // we also use the least restrictive generics possible. 867 unsafe impl<$($impl_generics)*> 868 $crate::init::__internal::HasPinData for $name<$($ty_generics)*> 869 where $($whr)* 870 { 871 type PinData = __ThePinData<$($ty_generics)*>; 872 873 unsafe fn __pin_data() -> Self::PinData { 874 __ThePinData { __phantom: ::core::marker::PhantomData } 875 } 876 } 877 878 // SAFETY: TODO. 879 unsafe impl<$($impl_generics)*> 880 $crate::init::__internal::PinData for __ThePinData<$($ty_generics)*> 881 where $($whr)* 882 { 883 type Datee = $name<$($ty_generics)*>; 884 } 885 886 // This struct will be used for the unpin analysis. Since only structurally pinned 887 // fields are relevant whether the struct should implement `Unpin`. 888 #[allow(dead_code)] 889 struct __Unpin <'__pin, $($impl_generics)*> 890 where $($whr)* 891 { 892 __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>, 893 __phantom: ::core::marker::PhantomData< 894 fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> 895 >, 896 // Only the pinned fields. 897 $($pinned)* 898 } 899 900 #[doc(hidden)] 901 impl<'__pin, $($impl_generics)*> ::core::marker::Unpin for $name<$($ty_generics)*> 902 where 903 __Unpin<'__pin, $($ty_generics)*>: ::core::marker::Unpin, 904 $($whr)* 905 {} 906 907 // We need to disallow normal `Drop` implementation, the exact behavior depends on 908 // whether `PinnedDrop` was specified as the parameter. 909 $crate::__pin_data!(drop_prevention: 910 @name($name), 911 @impl_generics($($impl_generics)*), 912 @ty_generics($($ty_generics)*), 913 @where($($whr)*), 914 @pinned_drop($($pinned_drop)?), 915 ); 916 }; 917 }; 918 // When no `PinnedDrop` was specified, then we have to prevent implementing drop. 919 (drop_prevention: 920 @name($name:ident), 921 @impl_generics($($impl_generics:tt)*), 922 @ty_generics($($ty_generics:tt)*), 923 @where($($whr:tt)*), 924 @pinned_drop(), 925 ) => { 926 // We prevent this by creating a trait that will be implemented for all types implementing 927 // `Drop`. Additionally we will implement this trait for the struct leading to a conflict, 928 // if it also implements `Drop` 929 trait MustNotImplDrop {} 930 #[expect(drop_bounds)] 931 impl<T: ::core::ops::Drop> MustNotImplDrop for T {} 932 impl<$($impl_generics)*> MustNotImplDrop for $name<$($ty_generics)*> 933 where $($whr)* {} 934 // We also take care to prevent users from writing a useless `PinnedDrop` implementation. 935 // They might implement `PinnedDrop` correctly for the struct, but forget to give 936 // `PinnedDrop` as the parameter to `#[pin_data]`. 937 #[expect(non_camel_case_types)] 938 trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {} 939 impl<T: $crate::init::PinnedDrop> 940 UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {} 941 impl<$($impl_generics)*> 942 UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for $name<$($ty_generics)*> 943 where $($whr)* {} 944 }; 945 // When `PinnedDrop` was specified we just implement `Drop` and delegate. 946 (drop_prevention: 947 @name($name:ident), 948 @impl_generics($($impl_generics:tt)*), 949 @ty_generics($($ty_generics:tt)*), 950 @where($($whr:tt)*), 951 @pinned_drop(PinnedDrop), 952 ) => { 953 impl<$($impl_generics)*> ::core::ops::Drop for $name<$($ty_generics)*> 954 where $($whr)* 955 { 956 fn drop(&mut self) { 957 // SAFETY: Since this is a destructor, `self` will not move after this function 958 // terminates, since it is inaccessible. 959 let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) }; 960 // SAFETY: Since this is a drop function, we can create this token to call the 961 // pinned destructor of this type. 962 let token = unsafe { $crate::init::__internal::OnlyCallFromDrop::new() }; 963 $crate::init::PinnedDrop::drop(pinned, token); 964 } 965 } 966 }; 967 // If some other parameter was specified, we emit a readable error. 968 (drop_prevention: 969 @name($name:ident), 970 @impl_generics($($impl_generics:tt)*), 971 @ty_generics($($ty_generics:tt)*), 972 @where($($whr:tt)*), 973 @pinned_drop($($rest:tt)*), 974 ) => { 975 compile_error!( 976 "Wrong parameters to `#[pin_data]`, expected nothing or `PinnedDrop`, got '{}'.", 977 stringify!($($rest)*), 978 ); 979 }; 980 (make_pin_data: 981 @pin_data($pin_data:ident), 982 @impl_generics($($impl_generics:tt)*), 983 @ty_generics($($ty_generics:tt)*), 984 @where($($whr:tt)*), 985 @pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?), 986 @not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?), 987 ) => { 988 // For every field, we create a projection function according to its projection type. If a 989 // field is structurally pinned, then it must be initialized via `PinInit`, if it is not 990 // structurally pinned, then it can be initialized via `Init`. 991 // 992 // The functions are `unsafe` to prevent accidentally calling them. 993 #[allow(dead_code)] 994 #[expect(clippy::missing_safety_doc)] 995 impl<$($impl_generics)*> $pin_data<$($ty_generics)*> 996 where $($whr)* 997 { 998 $( 999 $(#[$($p_attr)*])* 1000 $pvis unsafe fn $p_field<E>( 1001 self, 1002 slot: *mut $p_type, 1003 init: impl $crate::init::PinInit<$p_type, E>, 1004 ) -> ::core::result::Result<(), E> { 1005 // SAFETY: TODO. 1006 unsafe { $crate::init::PinInit::__pinned_init(init, slot) } 1007 } 1008 )* 1009 $( 1010 $(#[$($attr)*])* 1011 $fvis unsafe fn $field<E>( 1012 self, 1013 slot: *mut $type, 1014 init: impl $crate::init::Init<$type, E>, 1015 ) -> ::core::result::Result<(), E> { 1016 // SAFETY: TODO. 1017 unsafe { $crate::init::Init::__init(init, slot) } 1018 } 1019 )* 1020 } 1021 }; 1022 } 1023 1024 /// The internal init macro. Do not call manually! 1025 /// 1026 /// This is called by the `{try_}{pin_}init!` macros with various inputs. 1027 /// 1028 /// This macro has multiple internal call configurations, these are always the very first ident: 1029 /// - nothing: this is the base case and called by the `{try_}{pin_}init!` macros. 1030 /// - `with_update_parsed`: when the `..Zeroable::zeroed()` syntax has been handled. 1031 /// - `init_slot`: recursively creates the code that initializes all fields in `slot`. 1032 /// - `make_initializer`: recursively create the struct initializer that guarantees that every 1033 /// field has been initialized exactly once. 1034 #[doc(hidden)] 1035 #[macro_export] 1036 macro_rules! __init_internal { 1037 ( 1038 @this($($this:ident)?), 1039 @typ($t:path), 1040 @fields($($fields:tt)*), 1041 @error($err:ty), 1042 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1043 // case. 1044 @data($data:ident, $($use_data:ident)?), 1045 // `HasPinData` or `HasInitData`. 1046 @has_data($has_data:ident, $get_data:ident), 1047 // `pin_init_from_closure` or `init_from_closure`. 1048 @construct_closure($construct_closure:ident), 1049 @munch_fields(), 1050 ) => { 1051 $crate::__init_internal!(with_update_parsed: 1052 @this($($this)?), 1053 @typ($t), 1054 @fields($($fields)*), 1055 @error($err), 1056 @data($data, $($use_data)?), 1057 @has_data($has_data, $get_data), 1058 @construct_closure($construct_closure), 1059 @zeroed(), // Nothing means default behavior. 1060 ) 1061 }; 1062 ( 1063 @this($($this:ident)?), 1064 @typ($t:path), 1065 @fields($($fields:tt)*), 1066 @error($err:ty), 1067 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1068 // case. 1069 @data($data:ident, $($use_data:ident)?), 1070 // `HasPinData` or `HasInitData`. 1071 @has_data($has_data:ident, $get_data:ident), 1072 // `pin_init_from_closure` or `init_from_closure`. 1073 @construct_closure($construct_closure:ident), 1074 @munch_fields(..Zeroable::zeroed()), 1075 ) => { 1076 $crate::__init_internal!(with_update_parsed: 1077 @this($($this)?), 1078 @typ($t), 1079 @fields($($fields)*), 1080 @error($err), 1081 @data($data, $($use_data)?), 1082 @has_data($has_data, $get_data), 1083 @construct_closure($construct_closure), 1084 @zeroed(()), // `()` means zero all fields not mentioned. 1085 ) 1086 }; 1087 ( 1088 @this($($this:ident)?), 1089 @typ($t:path), 1090 @fields($($fields:tt)*), 1091 @error($err:ty), 1092 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1093 // case. 1094 @data($data:ident, $($use_data:ident)?), 1095 // `HasPinData` or `HasInitData`. 1096 @has_data($has_data:ident, $get_data:ident), 1097 // `pin_init_from_closure` or `init_from_closure`. 1098 @construct_closure($construct_closure:ident), 1099 @munch_fields($ignore:tt $($rest:tt)*), 1100 ) => { 1101 $crate::__init_internal!( 1102 @this($($this)?), 1103 @typ($t), 1104 @fields($($fields)*), 1105 @error($err), 1106 @data($data, $($use_data)?), 1107 @has_data($has_data, $get_data), 1108 @construct_closure($construct_closure), 1109 @munch_fields($($rest)*), 1110 ) 1111 }; 1112 (with_update_parsed: 1113 @this($($this:ident)?), 1114 @typ($t:path), 1115 @fields($($fields:tt)*), 1116 @error($err:ty), 1117 // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData` 1118 // case. 1119 @data($data:ident, $($use_data:ident)?), 1120 // `HasPinData` or `HasInitData`. 1121 @has_data($has_data:ident, $get_data:ident), 1122 // `pin_init_from_closure` or `init_from_closure`. 1123 @construct_closure($construct_closure:ident), 1124 @zeroed($($init_zeroed:expr)?), 1125 ) => {{ 1126 // We do not want to allow arbitrary returns, so we declare this type as the `Ok` return 1127 // type and shadow it later when we insert the arbitrary user code. That way there will be 1128 // no possibility of returning without `unsafe`. 1129 struct __InitOk; 1130 // Get the data about fields from the supplied type. 1131 // 1132 // SAFETY: TODO. 1133 let data = unsafe { 1134 use $crate::init::__internal::$has_data; 1135 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1136 // information that is associated to already parsed fragments, so a path fragment 1137 // cannot be used in this position. Doing the retokenization results in valid rust 1138 // code. 1139 $crate::init::macros::paste!($t::$get_data()) 1140 }; 1141 // Ensure that `data` really is of type `$data` and help with type inference: 1142 let init = $crate::init::__internal::$data::make_closure::<_, __InitOk, $err>( 1143 data, 1144 move |slot| { 1145 { 1146 // Shadow the structure so it cannot be used to return early. 1147 struct __InitOk; 1148 // If `$init_zeroed` is present we should zero the slot now and not emit an 1149 // error when fields are missing (since they will be zeroed). We also have to 1150 // check that the type actually implements `Zeroable`. 1151 $({ 1152 fn assert_zeroable<T: $crate::init::Zeroable>(_: *mut T) {} 1153 // Ensure that the struct is indeed `Zeroable`. 1154 assert_zeroable(slot); 1155 // SAFETY: The type implements `Zeroable` by the check above. 1156 unsafe { ::core::ptr::write_bytes(slot, 0, 1) }; 1157 $init_zeroed // This will be `()` if set. 1158 })? 1159 // Create the `this` so it can be referenced by the user inside of the 1160 // expressions creating the individual fields. 1161 $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? 1162 // Initialize every field. 1163 $crate::__init_internal!(init_slot($($use_data)?): 1164 @data(data), 1165 @slot(slot), 1166 @guards(), 1167 @munch_fields($($fields)*,), 1168 ); 1169 // We use unreachable code to ensure that all fields have been mentioned exactly 1170 // once, this struct initializer will still be type-checked and complain with a 1171 // very natural error message if a field is forgotten/mentioned more than once. 1172 #[allow(unreachable_code, clippy::diverging_sub_expression)] 1173 let _ = || { 1174 $crate::__init_internal!(make_initializer: 1175 @slot(slot), 1176 @type_name($t), 1177 @munch_fields($($fields)*,), 1178 @acc(), 1179 ); 1180 }; 1181 } 1182 Ok(__InitOk) 1183 } 1184 ); 1185 let init = move |slot| -> ::core::result::Result<(), $err> { 1186 init(slot).map(|__InitOk| ()) 1187 }; 1188 // SAFETY: TODO. 1189 let init = unsafe { $crate::init::$construct_closure::<_, $err>(init) }; 1190 init 1191 }}; 1192 (init_slot($($use_data:ident)?): 1193 @data($data:ident), 1194 @slot($slot:ident), 1195 @guards($($guards:ident,)*), 1196 @munch_fields($(..Zeroable::zeroed())? $(,)?), 1197 ) => { 1198 // Endpoint of munching, no fields are left. If execution reaches this point, all fields 1199 // have been initialized. Therefore we can now dismiss the guards by forgetting them. 1200 $(::core::mem::forget($guards);)* 1201 }; 1202 (init_slot($use_data:ident): // `use_data` is present, so we use the `data` to init fields. 1203 @data($data:ident), 1204 @slot($slot:ident), 1205 @guards($($guards:ident,)*), 1206 // In-place initialization syntax. 1207 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1208 ) => { 1209 let init = $val; 1210 // Call the initializer. 1211 // 1212 // SAFETY: `slot` is valid, because we are inside of an initializer closure, we 1213 // return when an error/panic occurs. 1214 // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`. 1215 unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? }; 1216 // Create the drop guard: 1217 // 1218 // We rely on macro hygiene to make it impossible for users to access this local variable. 1219 // We use `paste!` to create new hygiene for `$field`. 1220 $crate::init::macros::paste! { 1221 // SAFETY: We forget the guard later when initialization has succeeded. 1222 let [< __ $field _guard >] = unsafe { 1223 $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1224 }; 1225 1226 $crate::__init_internal!(init_slot($use_data): 1227 @data($data), 1228 @slot($slot), 1229 @guards([< __ $field _guard >], $($guards,)*), 1230 @munch_fields($($rest)*), 1231 ); 1232 } 1233 }; 1234 (init_slot(): // No `use_data`, so we use `Init::__init` directly. 1235 @data($data:ident), 1236 @slot($slot:ident), 1237 @guards($($guards:ident,)*), 1238 // In-place initialization syntax. 1239 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1240 ) => { 1241 let init = $val; 1242 // Call the initializer. 1243 // 1244 // SAFETY: `slot` is valid, because we are inside of an initializer closure, we 1245 // return when an error/panic occurs. 1246 unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? }; 1247 // Create the drop guard: 1248 // 1249 // We rely on macro hygiene to make it impossible for users to access this local variable. 1250 // We use `paste!` to create new hygiene for `$field`. 1251 $crate::init::macros::paste! { 1252 // SAFETY: We forget the guard later when initialization has succeeded. 1253 let [< __ $field _guard >] = unsafe { 1254 $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1255 }; 1256 1257 $crate::__init_internal!(init_slot(): 1258 @data($data), 1259 @slot($slot), 1260 @guards([< __ $field _guard >], $($guards,)*), 1261 @munch_fields($($rest)*), 1262 ); 1263 } 1264 }; 1265 (init_slot($($use_data:ident)?): 1266 @data($data:ident), 1267 @slot($slot:ident), 1268 @guards($($guards:ident,)*), 1269 // Init by-value. 1270 @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), 1271 ) => { 1272 { 1273 $(let $field = $val;)? 1274 // Initialize the field. 1275 // 1276 // SAFETY: The memory at `slot` is uninitialized. 1277 unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; 1278 } 1279 // Create the drop guard: 1280 // 1281 // We rely on macro hygiene to make it impossible for users to access this local variable. 1282 // We use `paste!` to create new hygiene for `$field`. 1283 $crate::init::macros::paste! { 1284 // SAFETY: We forget the guard later when initialization has succeeded. 1285 let [< __ $field _guard >] = unsafe { 1286 $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) 1287 }; 1288 1289 $crate::__init_internal!(init_slot($($use_data)?): 1290 @data($data), 1291 @slot($slot), 1292 @guards([< __ $field _guard >], $($guards,)*), 1293 @munch_fields($($rest)*), 1294 ); 1295 } 1296 }; 1297 (make_initializer: 1298 @slot($slot:ident), 1299 @type_name($t:path), 1300 @munch_fields(..Zeroable::zeroed() $(,)?), 1301 @acc($($acc:tt)*), 1302 ) => { 1303 // Endpoint, nothing more to munch, create the initializer. Since the users specified 1304 // `..Zeroable::zeroed()`, the slot will already have been zeroed and all field that have 1305 // not been overwritten are thus zero and initialized. We still check that all fields are 1306 // actually accessible by using the struct update syntax ourselves. 1307 // We are inside of a closure that is never executed and thus we can abuse `slot` to 1308 // get the correct type inference here: 1309 #[allow(unused_assignments)] 1310 unsafe { 1311 let mut zeroed = ::core::mem::zeroed(); 1312 // We have to use type inference here to make zeroed have the correct type. This does 1313 // not get executed, so it has no effect. 1314 ::core::ptr::write($slot, zeroed); 1315 zeroed = ::core::mem::zeroed(); 1316 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1317 // information that is associated to already parsed fragments, so a path fragment 1318 // cannot be used in this position. Doing the retokenization results in valid rust 1319 // code. 1320 $crate::init::macros::paste!( 1321 ::core::ptr::write($slot, $t { 1322 $($acc)* 1323 ..zeroed 1324 }); 1325 ); 1326 } 1327 }; 1328 (make_initializer: 1329 @slot($slot:ident), 1330 @type_name($t:path), 1331 @munch_fields($(,)?), 1332 @acc($($acc:tt)*), 1333 ) => { 1334 // Endpoint, nothing more to munch, create the initializer. 1335 // Since we are in the closure that is never called, this will never get executed. 1336 // We abuse `slot` to get the correct type inference here: 1337 // 1338 // SAFETY: TODO. 1339 unsafe { 1340 // Here we abuse `paste!` to retokenize `$t`. Declarative macros have some internal 1341 // information that is associated to already parsed fragments, so a path fragment 1342 // cannot be used in this position. Doing the retokenization results in valid rust 1343 // code. 1344 $crate::init::macros::paste!( 1345 ::core::ptr::write($slot, $t { 1346 $($acc)* 1347 }); 1348 ); 1349 } 1350 }; 1351 (make_initializer: 1352 @slot($slot:ident), 1353 @type_name($t:path), 1354 @munch_fields($field:ident <- $val:expr, $($rest:tt)*), 1355 @acc($($acc:tt)*), 1356 ) => { 1357 $crate::__init_internal!(make_initializer: 1358 @slot($slot), 1359 @type_name($t), 1360 @munch_fields($($rest)*), 1361 @acc($($acc)* $field: ::core::panic!(),), 1362 ); 1363 }; 1364 (make_initializer: 1365 @slot($slot:ident), 1366 @type_name($t:path), 1367 @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), 1368 @acc($($acc:tt)*), 1369 ) => { 1370 $crate::__init_internal!(make_initializer: 1371 @slot($slot), 1372 @type_name($t), 1373 @munch_fields($($rest)*), 1374 @acc($($acc)* $field: ::core::panic!(),), 1375 ); 1376 }; 1377 } 1378 1379 #[doc(hidden)] 1380 #[macro_export] 1381 macro_rules! __derive_zeroable { 1382 (parse_input: 1383 @sig( 1384 $(#[$($struct_attr:tt)*])* 1385 $vis:vis struct $name:ident 1386 $(where $($whr:tt)*)? 1387 ), 1388 @impl_generics($($impl_generics:tt)*), 1389 @ty_generics($($ty_generics:tt)*), 1390 @body({ 1391 $( 1392 $(#[$($field_attr:tt)*])* 1393 $field:ident : $field_ty:ty 1394 ),* $(,)? 1395 }), 1396 ) => { 1397 // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. 1398 #[automatically_derived] 1399 unsafe impl<$($impl_generics)*> $crate::init::Zeroable for $name<$($ty_generics)*> 1400 where 1401 $($($whr)*)? 1402 {} 1403 const _: () = { 1404 fn assert_zeroable<T: ?::core::marker::Sized + $crate::init::Zeroable>() {} 1405 fn ensure_zeroable<$($impl_generics)*>() 1406 where $($($whr)*)? 1407 { 1408 $(assert_zeroable::<$field_ty>();)* 1409 } 1410 }; 1411 }; 1412 } 1413