attr: Handle `rustc_const_{un}stable` properly
Since extern functions cannot be marked as const (they take no qualifiers) but some intrinsics are const, while still being `extern "rust-intrinsic", we need to be able to handle the `#[rustc_const_stable]` and `#[rustc_const_unstable]` attribute. Technically, this simply indicates that a certain intrinsic is constant and can be used in const contexts, such as `size_of` or `offset`. We also need to mark all const intrinsics with `rustc_const_stable` in the testsuite.
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@ -235,11 +235,48 @@ ConstChecker::check_function_call (HirId fn_id, Location locus)
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return;
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auto maybe_fn = mappings.lookup_hir_item (fn_id);
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if (!maybe_fn || maybe_fn->get_item_kind () != Item::ItemKind::Function)
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if (maybe_fn && maybe_fn->get_item_kind () != Item::ItemKind::Function)
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return;
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// There are const extern functions (intrinsics)
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// TODO: Should we check the ABI is only "rust intrinsics"? Is that handled
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// elsewhere?
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HirId parent_block;
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auto maybe_extern_item
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= mappings.lookup_hir_extern_item (fn_id, &parent_block);
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if (maybe_extern_item
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&& maybe_extern_item->get_extern_kind ()
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!= ExternalItem::ExternKind::Function)
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return;
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auto is_error = false;
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if (maybe_fn)
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{
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auto fn = static_cast<Function *> (maybe_fn);
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if (!fn->get_qualifiers ().is_const ())
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is_error = true;
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}
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if (maybe_extern_item)
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{
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{
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auto fn = static_cast<ExternalFunctionItem *> (maybe_extern_item);
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auto is_const_extern = std::any_of (
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fn->get_outer_attrs ().begin (), fn->get_outer_attrs ().end (),
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[] (const AST::Attribute &attr) {
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// `starts_with` in C++11...
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// FIXME: Is it really how we want to handle `rustc_const_stable`
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// and `rustc_const_unstable`?
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// TODO: Add these attributes to the attribute check and handle
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// `stable` and `unstable` as well
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return attr.get_path ().as_string ().rfind ("rustc_const_", 0) == 0;
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});
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if (!is_const_extern)
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is_error = true;
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}
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}
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if (is_error)
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rust_error_at (locus, "only functions marked as %<const%> are allowed to "
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"be called from constant contexts");
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}
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@ -522,6 +559,9 @@ ConstChecker::visit (Function &function)
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if (const_fn)
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const_context.enter (function.get_mappings ().get_hirid ());
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for (auto ¶m : function.get_function_params ())
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param.get_type ()->accept_vis (*this);
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function.get_definition ()->accept_vis (*this);
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if (const_fn)
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@ -0,0 +1,76 @@
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// { dg-additional-options "-w" }
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mod intrinsics {
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extern "rust-intrinsic" {
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pub fn wrapping_add<T>(a: T, b: T) -> T;
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pub fn rotate_left<T>(a: T, b: T) -> T;
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pub fn rotate_right<T>(a: T, b: T) -> T;
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pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
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}
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}
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mod mem {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
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pub fn transmute<T, U>(_: T) -> U;
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pub fn size_of<T>() -> usize;
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}
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}
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macro_rules! impl_uint {
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($($ty:ident = $lang:literal),*) => {
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$(
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impl $ty {
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pub fn wrapping_add(self, rhs: Self) -> Self {
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// intrinsics::wrapping_add(self, rhs)
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self + rhs
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}
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pub fn rotate_left(self, n: u32) -> Self {
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unsafe {
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intrinsics::rotate_left(self, n as Self)
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}
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}
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pub fn rotate_right(self, n: u32) -> Self {
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unsafe {
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intrinsics::rotate_right(self, n as Self)
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}
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}
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pub fn to_le(self) -> Self {
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#[cfg(target_endian = "little")]
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{
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self
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}
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}
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pub const fn from_le_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
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// { dg-error "only functions marked as .const. are allowed to be called from constant contexts" "" { target *-*-* } .-1 }
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Self::from_le(Self::from_ne_bytes(bytes))
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}
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pub const fn from_le(x: Self) -> Self {
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#[cfg(target_endian = "little")]
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{
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x
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}
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}
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pub const fn from_ne_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
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// { dg-error "only functions marked as .const. are allowed to be called from constant contexts" "" { target *-*-* } .-1 }
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unsafe { mem::transmute(bytes) }
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}
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}
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)*
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}
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}
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impl_uint!(
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u8 = "u8",
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u16 = "u16",
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u32 = "u32",
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u64 = "u64",
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u128 = "u128",
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usize = "usize"
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);
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@ -1,4 +1,5 @@
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -4,6 +4,7 @@ extern "C" {
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mod intrinsics {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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}
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@ -1,5 +1,6 @@
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// { dg-additional-options "-w" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -1,16 +1,22 @@
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// { dg-additional-options "-w" }
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mod intrinsics {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
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pub fn wrapping_add<T>(a: T, b: T) -> T;
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#[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
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pub fn rotate_left<T>(a: T, b: T) -> T;
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#[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
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pub fn rotate_right<T>(a: T, b: T) -> T;
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
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}
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}
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mod mem {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
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fn transmute<T, U>(_: T) -> U;
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#[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
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fn size_of<T>() -> usize;
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}
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}
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@ -1,5 +1,6 @@
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// { dg-additional-options "-w" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -1,5 +1,6 @@
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// { dg-additional-options "-w" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -1,6 +1,7 @@
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// { dg-additional-options "-w" }
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// { dg-output "slice_access=3\n" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -2,6 +2,7 @@
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// { dg-output "" }
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mod intrinsics {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
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}
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}
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@ -1,5 +1,6 @@
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// { dg-additional-options "-w" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -1,5 +1,6 @@
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// { dg-additional-options "-w" }
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
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pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
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}
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@ -2,6 +2,7 @@
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// { dg-output "t1sz=5 t2sz=10" }
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mod mem {
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extern "rust-intrinsic" {
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#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
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fn transmute<T, U>(_: T) -> U;
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}
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}
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