diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs index a889eff75c0..721a2d26a71 100644 --- a/src/libcore/intrinsics.rs +++ b/src/libcore/intrinsics.rs @@ -1007,6 +1007,16 @@ extern "rust-intrinsic" { /// This will statically either panic, or do nothing. pub fn panic_if_uninhabited(); + /// A guard for unsafe functions that cannot ever be executed if `T` does not permit + /// zero-initialization: This will statically either panic, or do nothing. + #[cfg(not(bootstrap))] + pub fn panic_if_zero_invalid(); + + /// A guard for unsafe functions that cannot ever be executed if `T` has invalid + /// bit patterns: This will statically either panic, or do nothing. + #[cfg(not(bootstrap))] + pub fn panic_if_any_invalid(); + /// Gets a reference to a static `Location` indicating where it was called. #[rustc_const_unstable(feature = "const_caller_location", issue = "47809")] pub fn caller_location() -> &'static crate::panic::Location<'static>; diff --git a/src/libcore/mem/mod.rs b/src/libcore/mem/mod.rs index 90144d11dc9..8add875dcbe 100644 --- a/src/libcore/mem/mod.rs +++ b/src/libcore/mem/mod.rs @@ -496,6 +496,9 @@ pub const fn needs_drop() -> bool { #[allow(deprecated)] #[rustc_diagnostic_item = "mem_zeroed"] pub unsafe fn zeroed() -> T { + #[cfg(not(bootstrap))] + intrinsics::panic_if_zero_invalid::(); + #[cfg(bootstrap)] intrinsics::panic_if_uninhabited::(); intrinsics::init() } @@ -529,6 +532,9 @@ pub unsafe fn zeroed() -> T { #[allow(deprecated)] #[rustc_diagnostic_item = "mem_uninitialized"] pub unsafe fn uninitialized() -> T { + #[cfg(not(bootstrap))] + intrinsics::panic_if_any_invalid::(); + #[cfg(bootstrap)] intrinsics::panic_if_uninhabited::(); intrinsics::uninit() } diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs index e257b48f111..dedb3035ced 100644 --- a/src/librustc/ty/layout.rs +++ b/src/librustc/ty/layout.rs @@ -1904,36 +1904,6 @@ impl<'tcx, T: HasTyCtxt<'tcx>> HasTyCtxt<'tcx> for LayoutCx<'tcx, T> { } } -pub trait MaybeResult { - type Error; - - fn from(x: Result) -> Self; - fn to_result(self) -> Result; -} - -impl MaybeResult for T { - type Error = !; - - fn from(x: Result) -> Self { - let Ok(x) = x; - x - } - fn to_result(self) -> Result { - Ok(self) - } -} - -impl MaybeResult for Result { - type Error = E; - - fn from(x: Result) -> Self { - x - } - fn to_result(self) -> Result { - self - } -} - pub type TyLayout<'tcx> = ::rustc_target::abi::TyLayout<'tcx, Ty<'tcx>>; impl<'tcx> LayoutOf for LayoutCx<'tcx, TyCtxt<'tcx>> { diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs index a1b54607b80..c8d352cd2dd 100644 --- a/src/librustc_codegen_ssa/mir/block.rs +++ b/src/librustc_codegen_ssa/mir/block.rs @@ -434,6 +434,89 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { helper.do_call(self, &mut bx, fn_abi, llfn, &args, None, cleanup); } + /// Returns `true` if this is indeed a panic intrinsic and codegen is done. + fn codegen_panic_intrinsic( + &mut self, + helper: &TerminatorCodegenHelper<'tcx>, + bx: &mut Bx, + intrinsic: Option<&str>, + instance: Option>, + span: Span, + destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>, + cleanup: Option, + ) -> bool { + // Emit a panic or a no-op for `panic_if_uninhabited`. + // These are intrinsics that compile to panics so that we can get a message + // which mentions the offending type, even from a const context. + #[derive(Debug, PartialEq)] + enum PanicIntrinsic { + IfUninhabited, + IfZeroInvalid, + IfAnyInvalid, + }; + let panic_intrinsic = intrinsic.and_then(|i| match i { + // FIXME: Move to symbols instead of strings. + "panic_if_uninhabited" => Some(PanicIntrinsic::IfUninhabited), + "panic_if_zero_invalid" => Some(PanicIntrinsic::IfZeroInvalid), + "panic_if_any_invalid" => Some(PanicIntrinsic::IfAnyInvalid), + _ => None, + }); + if let Some(intrinsic) = panic_intrinsic { + use PanicIntrinsic::*; + let ty = instance.unwrap().substs.type_at(0); + let layout = bx.layout_of(ty); + let do_panic = match intrinsic { + IfUninhabited => layout.abi.is_uninhabited(), + // We unwrap as the error type is `!`. + IfZeroInvalid => !layout.might_permit_raw_init(bx, /*zero:*/ true).unwrap(), + // We unwrap as the error type is `!`. + IfAnyInvalid => !layout.might_permit_raw_init(bx, /*zero:*/ false).unwrap(), + }; + if do_panic { + let msg_str = if layout.abi.is_uninhabited() { + // Use this error even for the other intrinsics as it is more precise. + format!("attempted to instantiate uninhabited type `{}`", ty) + } else if intrinsic == IfZeroInvalid { + format!("attempted to zero-initialize type `{}`, which is invalid", ty) + } else { + format!("attempted to leave type `{}` uninitialized, which is invalid", ty) + }; + let msg = bx.const_str(Symbol::intern(&msg_str)); + let location = self.get_caller_location(bx, span).immediate(); + + // Obtain the panic entry point. + // FIXME: dedup this with `codegen_assert_terminator` above. + let def_id = + common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem); + let instance = ty::Instance::mono(bx.tcx(), def_id); + let fn_abi = FnAbi::of_instance(bx, instance, &[]); + let llfn = bx.get_fn_addr(instance); + + if let Some((_, target)) = destination.as_ref() { + helper.maybe_sideeffect(self.mir, bx, &[*target]); + } + // Codegen the actual panic invoke/call. + helper.do_call( + self, + bx, + fn_abi, + llfn, + &[msg.0, msg.1, location], + destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)), + cleanup, + ); + } else { + // a NOP + let target = destination.as_ref().unwrap().1; + helper.maybe_sideeffect(self.mir, bx, &[target]); + helper.funclet_br(self, bx, target) + } + true + } else { + false + } + } + fn codegen_call_terminator( &mut self, helper: TerminatorCodegenHelper<'tcx>, @@ -520,41 +603,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { bug!("`miri_start_panic` should never end up in compiled code"); } - // Emit a panic or a no-op for `panic_if_uninhabited`. - if intrinsic == Some("panic_if_uninhabited") { - let ty = instance.unwrap().substs.type_at(0); - let layout = bx.layout_of(ty); - if layout.abi.is_uninhabited() { - let msg_str = format!("Attempted to instantiate uninhabited type {}", ty); - let msg = bx.const_str(Symbol::intern(&msg_str)); - let location = self.get_caller_location(&mut bx, span).immediate(); - - // Obtain the panic entry point. - let def_id = - common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem); - let instance = ty::Instance::mono(bx.tcx(), def_id); - let fn_abi = FnAbi::of_instance(&bx, instance, &[]); - let llfn = bx.get_fn_addr(instance); - - if let Some((_, target)) = destination.as_ref() { - helper.maybe_sideeffect(self.mir, &mut bx, &[*target]); - } - // Codegen the actual panic invoke/call. - helper.do_call( - self, - &mut bx, - fn_abi, - llfn, - &[msg.0, msg.1, location], - destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)), - cleanup, - ); - } else { - // a NOP - let target = destination.as_ref().unwrap().1; - helper.maybe_sideeffect(self.mir, &mut bx, &[target]); - helper.funclet_br(self, &mut bx, target) - } + if self.codegen_panic_intrinsic( + &helper, + &mut bx, + intrinsic, + instance, + span, + destination, + cleanup, + ) { return; } diff --git a/src/librustc_index/vec.rs b/src/librustc_index/vec.rs index 1dfe97238a3..7020939fa20 100644 --- a/src/librustc_index/vec.rs +++ b/src/librustc_index/vec.rs @@ -196,7 +196,7 @@ macro_rules! newtype_index { #[inline] fn index(self) -> usize { - usize::from(self) + self.as_usize() } } diff --git a/src/librustc_target/abi/mod.rs b/src/librustc_target/abi/mod.rs index a3a9b542767..2f8bbd66c32 100644 --- a/src/librustc_target/abi/mod.rs +++ b/src/librustc_target/abi/mod.rs @@ -937,6 +937,7 @@ impl<'a, Ty> Deref for TyLayout<'a, Ty> { } } +/// Trait for context types that can compute layouts of things. pub trait LayoutOf { type Ty; type TyLayout; @@ -947,6 +948,38 @@ pub trait LayoutOf { } } +/// The `TyLayout` above will always be a `MaybeResult>`. +/// We can't add the bound due to the lifetime, but this trait is still useful when +/// writing code that's generic over the `LayoutOf` impl. +pub trait MaybeResult { + type Error; + + fn from(x: Result) -> Self; + fn to_result(self) -> Result; +} + +impl MaybeResult for T { + type Error = !; + + fn from(Ok(x): Result) -> Self { + x + } + fn to_result(self) -> Result { + Ok(self) + } +} + +impl MaybeResult for Result { + type Error = E; + + fn from(x: Result) -> Self { + x + } + fn to_result(self) -> Result { + self + } +} + #[derive(Copy, Clone, PartialEq, Eq)] pub enum PointerKind { /// Most general case, we know no restrictions to tell LLVM. @@ -987,6 +1020,9 @@ impl<'a, Ty> TyLayout<'a, Ty> { { Ty::for_variant(self, cx, variant_index) } + + /// Callers might want to use `C: LayoutOf>` + /// to allow recursion (see `might_permit_zero_init` below for an example). pub fn field(self, cx: &C, i: usize) -> C::TyLayout where Ty: TyLayoutMethods<'a, C>, @@ -994,6 +1030,7 @@ impl<'a, Ty> TyLayout<'a, Ty> { { Ty::field(self, cx, i) } + pub fn pointee_info_at(self, cx: &C, offset: Size) -> Option where Ty: TyLayoutMethods<'a, C>, @@ -1017,4 +1054,52 @@ impl<'a, Ty> TyLayout<'a, Ty> { Abi::Aggregate { sized } => sized && self.size.bytes() == 0, } } + + /// Determines if this type permits "raw" initialization by just transmuting some + /// memory into an instance of `T`. + /// `zero` indicates if the memory is zero-initialized, or alternatively + /// left entirely uninitialized. + /// This is conservative: in doubt, it will answer `true`. + /// + /// FIXME: Once we removed all the conservatism, we could alternatively + /// create an all-0/all-undef constant and run the const value validator to see if + /// this is a valid value for the given type. + pub fn might_permit_raw_init(self, cx: &C, zero: bool) -> Result + where + Self: Copy, + Ty: TyLayoutMethods<'a, C>, + C: LayoutOf> + HasDataLayout, + { + let scalar_allows_raw_init = move |s: &Scalar| -> bool { + if zero { + let range = &s.valid_range; + // The range must contain 0. + range.contains(&0) || (*range.start() > *range.end()) // wrap-around allows 0 + } else { + // The range must include all values. `valid_range_exclusive` handles + // the wrap-around using target arithmetic; with wrap-around then the full + // range is one where `start == end`. + let range = s.valid_range_exclusive(cx); + range.start == range.end + } + }; + + // Check the ABI. + let valid = match &self.abi { + Abi::Uninhabited => false, // definitely UB + Abi::Scalar(s) => scalar_allows_raw_init(s), + Abi::ScalarPair(s1, s2) => scalar_allows_raw_init(s1) && scalar_allows_raw_init(s2), + Abi::Vector { element: s, count } => *count == 0 || scalar_allows_raw_init(s), + Abi::Aggregate { .. } => true, // Cannot be excluded *right now*. + }; + if !valid { + // This is definitely not okay. + trace!("might_permit_raw_init({:?}, zero={}): not valid", self.details, zero); + return Ok(false); + } + + // If we have not found an error yet, we need to recursively descend. + // FIXME(#66151): For now, we are conservative and do not do this. + Ok(true) + } } diff --git a/src/librustc_target/lib.rs b/src/librustc_target/lib.rs index 71150e74f70..3c397eb444d 100644 --- a/src/librustc_target/lib.rs +++ b/src/librustc_target/lib.rs @@ -10,6 +10,9 @@ #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")] #![feature(bool_to_option)] #![feature(nll)] +#![feature(never_type)] +#![feature(associated_type_bounds)] +#![feature(exhaustive_patterns)] #[macro_use] extern crate log; diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs index 3572eda5c13..d2a358c3e09 100644 --- a/src/librustc_typeck/check/intrinsic.rs +++ b/src/librustc_typeck/check/intrinsic.rs @@ -147,7 +147,9 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) { ), "rustc_peek" => (1, vec![param(0)], param(0)), "caller_location" => (0, vec![], tcx.caller_location_ty()), - "panic_if_uninhabited" => (1, Vec::new(), tcx.mk_unit()), + "panic_if_uninhabited" | "panic_if_zero_invalid" | "panic_if_any_invalid" => { + (1, Vec::new(), tcx.mk_unit()) + } "init" => (1, Vec::new(), param(0)), "uninit" => (1, Vec::new(), param(0)), "forget" => (1, vec![param(0)], tcx.mk_unit()), diff --git a/src/test/ui/intrinsics/panic-uninitialized-zeroed.rs b/src/test/ui/intrinsics/panic-uninitialized-zeroed.rs new file mode 100644 index 00000000000..02f8ecaa4ee --- /dev/null +++ b/src/test/ui/intrinsics/panic-uninitialized-zeroed.rs @@ -0,0 +1,170 @@ +// run-pass +// ignore-wasm32-bare compiled with panic=abort by default + +// This test checks panic emitted from `mem::{uninitialized,zeroed}`. + +#![feature(never_type)] +#![allow(deprecated, invalid_value)] + +use std::{ + mem::{self, MaybeUninit, ManuallyDrop}, + panic, + ptr::NonNull, + num, +}; + +#[allow(dead_code)] +struct Foo { + x: u8, + y: !, +} + +enum Bar {} + +#[allow(dead_code)] +enum OneVariant { Variant(i32) } + +// An enum with ScalarPair layout +#[allow(dead_code)] +enum LR { + Left(i64), + Right(i64), +} +#[allow(dead_code, non_camel_case_types)] +enum LR_NonZero { + Left(num::NonZeroI64), + Right(num::NonZeroI64), +} + +fn test_panic_msg(op: impl (FnOnce() -> T) + panic::UnwindSafe, msg: &str) { + let err = panic::catch_unwind(op).err(); + assert_eq!( + err.as_ref().and_then(|a| a.downcast_ref::()).map(|s| &**s), + Some(msg) + ); +} + +fn main() { + unsafe { + // Uninhabited types + test_panic_msg( + || mem::uninitialized::(), + "attempted to instantiate uninhabited type `!`" + ); + test_panic_msg( + || mem::zeroed::(), + "attempted to instantiate uninhabited type `!`" + ); + test_panic_msg( + || MaybeUninit::::uninit().assume_init(), + "attempted to instantiate uninhabited type `!`" + ); + + test_panic_msg( + || mem::uninitialized::(), + "attempted to instantiate uninhabited type `Foo`" + ); + test_panic_msg( + || mem::zeroed::(), + "attempted to instantiate uninhabited type `Foo`" + ); + test_panic_msg( + || MaybeUninit::::uninit().assume_init(), + "attempted to instantiate uninhabited type `Foo`" + ); + + test_panic_msg( + || mem::uninitialized::(), + "attempted to instantiate uninhabited type `Bar`" + ); + test_panic_msg( + || mem::zeroed::(), + "attempted to instantiate uninhabited type `Bar`" + ); + test_panic_msg( + || MaybeUninit::::uninit().assume_init(), + "attempted to instantiate uninhabited type `Bar`" + ); + + // Types that do not like zero-initialziation + test_panic_msg( + || mem::uninitialized::(), + "attempted to leave type `fn()` uninitialized, which is invalid" + ); + test_panic_msg( + || mem::zeroed::(), + "attempted to zero-initialize type `fn()`, which is invalid" + ); + + test_panic_msg( + || mem::uninitialized::<*const dyn Send>(), + "attempted to leave type `*const dyn std::marker::Send` uninitialized, which is invalid" + ); + test_panic_msg( + || mem::zeroed::<*const dyn Send>(), + "attempted to zero-initialize type `*const dyn std::marker::Send`, which is invalid" + ); + + /* FIXME(#66151) we conservatively do not error here yet. + test_panic_msg( + || mem::uninitialized::(), + "attempted to leave type `LR_NonZero` uninitialized, which is invalid" + ); + test_panic_msg( + || mem::zeroed::(), + "attempted to zero-initialize type `LR_NonZero`, which is invalid" + ); + + test_panic_msg( + || mem::uninitialized::>(), + "attempted to leave type `std::mem::ManuallyDrop` uninitialized, \ + which is invalid" + ); + test_panic_msg( + || mem::zeroed::>(), + "attempted to zero-initialize type `std::mem::ManuallyDrop`, \ + which is invalid" + ); + + test_panic_msg( + || mem::uninitialized::<(NonNull, u32, u32)>(), + "attempted to leave type `(std::ptr::NonNull, u32, u32)` uninitialized, \ + which is invalid" + ); + test_panic_msg( + || mem::zeroed::<(NonNull, u32, u32)>(), + "attempted to zero-initialize type `(std::ptr::NonNull, u32, u32)`, \ + which is invalid" + ); + */ + + // Types that can be zero, but not uninit. + test_panic_msg( + || mem::uninitialized::(), + "attempted to leave type `bool` uninitialized, which is invalid" + ); + test_panic_msg( + || mem::uninitialized::(), + "attempted to leave type `LR` uninitialized, which is invalid" + ); + test_panic_msg( + || mem::uninitialized::>(), + "attempted to leave type `std::mem::ManuallyDrop` uninitialized, which is invalid" + ); + + // Some things that should work. + let _val = mem::zeroed::(); + let _val = mem::zeroed::(); + let _val = mem::zeroed::>(); + let _val = mem::zeroed::(); + let _val = mem::zeroed::>(); + let _val = mem::zeroed::>>(); + let _val = mem::uninitialized::>(); + + // These are UB because they have not been officially blessed, but we await the resolution + // of before doing + // anything about that. + let _val = mem::uninitialized::(); + let _val = mem::uninitialized::<*const ()>(); + } +} diff --git a/src/test/ui/never_type/panic-uninitialized-zeroed.rs b/src/test/ui/never_type/panic-uninitialized-zeroed.rs deleted file mode 100644 index e0c30160b9e..00000000000 --- a/src/test/ui/never_type/panic-uninitialized-zeroed.rs +++ /dev/null @@ -1,102 +0,0 @@ -// run-pass -// ignore-wasm32-bare compiled with panic=abort by default -// This test checks that instantiating an uninhabited type via `mem::{uninitialized,zeroed}` results -// in a runtime panic. - -#![feature(never_type)] -#![allow(deprecated, invalid_value)] - -use std::{mem, panic}; - -#[allow(dead_code)] -struct Foo { - x: u8, - y: !, -} - -enum Bar {} - -fn main() { - unsafe { - assert_eq!( - panic::catch_unwind(|| { - mem::uninitialized::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type !" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::zeroed::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type !" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::MaybeUninit::::uninit().assume_init() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type !" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::uninitialized::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Foo" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::zeroed::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Foo" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::MaybeUninit::::uninit().assume_init() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Foo" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::uninitialized::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Bar" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::zeroed::() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Bar" - })), - Some(true) - ); - - assert_eq!( - panic::catch_unwind(|| { - mem::MaybeUninit::::uninit().assume_init() - }).err().and_then(|a| a.downcast_ref::().map(|s| { - s == "Attempted to instantiate uninhabited type Bar" - })), - Some(true) - ); - } -}