diff --git a/compiler/rustc_error_codes/src/error_codes/E0795.md b/compiler/rustc_error_codes/src/error_codes/E0795.md index 20f51441c29..ad77d72c913 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0795.md +++ b/compiler/rustc_error_codes/src/error_codes/E0795.md @@ -3,7 +3,7 @@ Invalid argument for the `offset_of!` macro. Erroneous code example: ```compile_fail,E0795 -#![feature(offset_of, offset_of_enum)] +#![feature(offset_of_enum, offset_of_nested)] let x = std::mem::offset_of!(Option, Some); ``` @@ -16,7 +16,7 @@ The offset of the contained `u8` in the `Option` can be found by specifying the field name `0`: ``` -#![feature(offset_of, offset_of_enum)] +#![feature(offset_of_enum, offset_of_nested)] let x: usize = std::mem::offset_of!(Option, Some.0); ``` diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs index 2f2b551e6ec..c512ccc90db 100644 --- a/compiler/rustc_feature/src/unstable.rs +++ b/compiler/rustc_feature/src/unstable.rs @@ -550,6 +550,8 @@ declare_features! ( (unstable, object_safe_for_dispatch, "1.40.0", Some(43561)), /// Allows using enums in offset_of! (unstable, offset_of_enum, "1.75.0", Some(106655)), + /// Allows using multiple nested field accesses in offset_of! + (unstable, offset_of_nested, "CURRENT_RUSTC_VERSION", Some(106655)), /// Allows using `#[optimize(X)]`. (unstable, optimize_attribute, "1.34.0", Some(54882)), /// Allows macro attributes on expressions, statements and non-inline modules. diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs index 4b1ad28f094..242e8dc95e2 100644 --- a/compiler/rustc_hir_typeck/src/expr.rs +++ b/compiler/rustc_hir_typeck/src/expr.rs @@ -3246,6 +3246,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ) -> Ty<'tcx> { let container = self.to_ty(container).normalized; + if let Some(ident_2) = fields.get(1) + && !self.tcx.features().offset_of_nested + { + rustc_session::parse::feature_err( + &self.tcx.sess.parse_sess, + sym::offset_of_nested, + ident_2.span, + "only a single ident or integer is stable as the field in offset_of", + ) + .emit(); + } + let mut field_indices = Vec::with_capacity(fields.len()); let mut current_container = container; let mut fields = fields.into_iter(); diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 44795022cba..7b0138d50ba 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -1153,6 +1153,7 @@ symbols! { offset, offset_of, offset_of_enum, + offset_of_nested, ok_or_else, omit_gdb_pretty_printer_section, on, diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index 1a8f245c8be..81bf6f28693 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -111,6 +111,7 @@ // // Library features: // tidy-alphabetical-start +#![cfg_attr(not(bootstrap), feature(offset_of_nested))] #![feature(char_indices_offset)] #![feature(const_align_of_val)] #![feature(const_align_of_val_raw)] @@ -176,7 +177,6 @@ #![feature(isqrt)] #![feature(maybe_uninit_uninit_array)] #![feature(non_null_convenience)] -#![feature(offset_of)] #![feature(offset_of_enum)] #![feature(panic_internals)] #![feature(ptr_alignment_type)] diff --git a/library/core/src/mem/mod.rs b/library/core/src/mem/mod.rs index 407954001e4..f04ccce40f1 100644 --- a/library/core/src/mem/mod.rs +++ b/library/core/src/mem/mod.rs @@ -1303,11 +1303,12 @@ impl SizedTypeProperties for T {} /// Enum variants may be traversed as if they were fields. Variants themselves do /// not have an offset. /// +/// However, on stable only a single field name is supported, which blocks the use of +/// enum support. +/// /// Visibility is respected - all types and fields must be visible to the call site: /// /// ``` -/// #![feature(offset_of)] -/// /// mod nested { /// #[repr(C)] /// pub struct Struct { @@ -1330,8 +1331,6 @@ impl SizedTypeProperties for T {} /// not *identical*, e.g.: /// /// ``` -/// #![feature(offset_of)] -/// /// struct Wrapper(T, U); /// /// type A = Wrapper; @@ -1359,8 +1358,7 @@ impl SizedTypeProperties for T {} /// # Examples /// /// ``` -/// #![feature(offset_of)] -/// # #![feature(offset_of_enum)] +/// #![feature(offset_of_enum, offset_of_nested)] /// /// use std::mem; /// #[repr(C)] @@ -1396,7 +1394,7 @@ impl SizedTypeProperties for T {} /// assert_eq!(mem::offset_of!(Option<&u8>, Some.0), 0); /// ``` #[cfg(not(bootstrap))] -#[unstable(feature = "offset_of", issue = "106655")] +#[stable(feature = "offset_of", since = "CURRENT_RUSTC_VERSION")] #[allow_internal_unstable(builtin_syntax, hint_must_use)] pub macro offset_of($Container:ty, $($fields:expr)+ $(,)?) { // The `{}` is for better error messages @@ -1404,7 +1402,7 @@ pub macro offset_of($Container:ty, $($fields:expr)+ $(,)?) { } #[cfg(bootstrap)] -#[unstable(feature = "offset_of", issue = "106655")] +#[stable(feature = "offset_of", since = "CURRENT_RUSTC_VERSION")] #[allow_internal_unstable(builtin_syntax, hint_must_use)] #[allow(missing_docs)] pub macro offset_of($Container:ty, $($fields:tt).+ $(,)?) { diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs index 8604d41eb68..02af3e6f947 100644 --- a/library/core/tests/lib.rs +++ b/library/core/tests/lib.rs @@ -115,7 +115,6 @@ #![feature(utf8_chunks)] #![feature(is_ascii_octdigit)] #![feature(get_many_mut)] -#![feature(offset_of)] #![feature(iter_map_windows)] #![allow(internal_features)] #![deny(unsafe_op_in_unsafe_fn)] diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index 7a8d9d0ceec..4b33ad5dfe0 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -329,7 +329,6 @@ #![feature(maybe_uninit_slice)] #![feature(maybe_uninit_uninit_array)] #![feature(maybe_uninit_write_slice)] -#![feature(offset_of)] #![feature(panic_can_unwind)] #![feature(panic_info_message)] #![feature(panic_internals)] diff --git a/tests/ui/feature-gates/feature-gate-offset-of-enum.rs b/tests/ui/feature-gates/feature-gate-offset-of-enum.rs index e19dcf9f6a5..1f2f7ee1e19 100644 --- a/tests/ui/feature-gates/feature-gate-offset-of-enum.rs +++ b/tests/ui/feature-gates/feature-gate-offset-of-enum.rs @@ -1,4 +1,4 @@ -#![feature(offset_of)] +#![feature(offset_of_nested)] use std::mem::offset_of; diff --git a/tests/ui/feature-gates/feature-gate-offset-of-nested.rs b/tests/ui/feature-gates/feature-gate-offset-of-nested.rs new file mode 100644 index 00000000000..c4eb4720fde --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-offset-of-nested.rs @@ -0,0 +1,28 @@ +#![feature(offset_of_enum)] + +use std::mem::offset_of; + +struct S { + a: u8, + b: (u8, u8), + c: T, +} + +struct T { + t: &'static str, +} + +enum Alpha { + One(u8), + Two(u8), +} + +fn main() { + offset_of!(Alpha, Two.0); //~ ERROR only a single ident or integer is stable as the field in offset_of + offset_of!(S, a); + offset_of!((u8, S), 1); + offset_of!((u32, (S, T)), 1.1); //~ ERROR only a single ident or integer is stable as the field in offset_of + offset_of!(S, b.0); //~ ERROR only a single ident or integer is stable as the field in offset_of + offset_of!((S, ()), 0.c); //~ ERROR only a single ident or integer is stable as the field in offset_of + offset_of!(S, c.t); //~ ERROR only a single ident or integer is stable as the field in offset_of +} diff --git a/tests/ui/feature-gates/feature-gate-offset-of-nested.stderr b/tests/ui/feature-gates/feature-gate-offset-of-nested.stderr new file mode 100644 index 00000000000..ebc251fd663 --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-offset-of-nested.stderr @@ -0,0 +1,55 @@ +error[E0658]: only a single ident or integer is stable as the field in offset_of + --> $DIR/feature-gate-offset-of-nested.rs:21:27 + | +LL | offset_of!(Alpha, Two.0); + | ^ + | + = note: see issue #106655 for more information + = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable + +error[E0658]: only a single ident or integer is stable as the field in offset_of + --> $DIR/feature-gate-offset-of-nested.rs:24:33 + | +LL | offset_of!((u32, (S, T)), 1.1); + | _____----------------------------^- + | | | + | | in this macro invocation +LL | | offset_of!(S, b.0); +LL | | offset_of!((S, ()), 0.c); +LL | | offset_of!(S, c.t); +... | + | + = note: see issue #106655 for more information + = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable + = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) + +error[E0658]: only a single ident or integer is stable as the field in offset_of + --> $DIR/feature-gate-offset-of-nested.rs:25:21 + | +LL | offset_of!(S, b.0); + | ^ + | + = note: see issue #106655 for more information + = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable + +error[E0658]: only a single ident or integer is stable as the field in offset_of + --> $DIR/feature-gate-offset-of-nested.rs:26:27 + | +LL | offset_of!((S, ()), 0.c); + | ^ + | + = note: see issue #106655 for more information + = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable + +error[E0658]: only a single ident or integer is stable as the field in offset_of + --> $DIR/feature-gate-offset-of-nested.rs:27:21 + | +LL | offset_of!(S, c.t); + | ^ + | + = note: see issue #106655 for more information + = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable + +error: aborting due to 5 previous errors + +For more information about this error, try `rustc --explain E0658`. diff --git a/tests/ui/lint/dead-code/offset-of-correct-param-env.rs b/tests/ui/lint/dead-code/offset-of-correct-param-env.rs index 2c6fcef2500..ae81a252439 100644 --- a/tests/ui/lint/dead-code/offset-of-correct-param-env.rs +++ b/tests/ui/lint/dead-code/offset-of-correct-param-env.rs @@ -1,6 +1,6 @@ // check-pass -#![feature(offset_of)] +#![feature(offset_of_nested)] #![deny(dead_code)] // This struct contains a projection that can only be normalized after getting the field type. diff --git a/tests/ui/lint/dead-code/offset-of.rs b/tests/ui/lint/dead-code/offset-of.rs index da91de3862f..5269426d2ff 100644 --- a/tests/ui/lint/dead-code/offset-of.rs +++ b/tests/ui/lint/dead-code/offset-of.rs @@ -1,4 +1,4 @@ -#![feature(offset_of)] +#![feature(offset_of_nested)] #![deny(dead_code)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-arg-count.rs b/tests/ui/offset-of/offset-of-arg-count.rs index 7b92698c25e..c86e61a61a7 100644 --- a/tests/ui/offset-of/offset-of-arg-count.rs +++ b/tests/ui/offset-of/offset-of-arg-count.rs @@ -1,5 +1,3 @@ -#![feature(offset_of)] - use std::mem::offset_of; fn main() { diff --git a/tests/ui/offset-of/offset-of-arg-count.stderr b/tests/ui/offset-of/offset-of-arg-count.stderr index af0d42de30d..4cb24b3d034 100644 --- a/tests/ui/offset-of/offset-of-arg-count.stderr +++ b/tests/ui/offset-of/offset-of-arg-count.stderr @@ -1,5 +1,5 @@ error: unexpected end of macro invocation - --> $DIR/offset-of-arg-count.rs:6:34 + --> $DIR/offset-of-arg-count.rs:4:34 | LL | offset_of!(NotEnoughArguments); | ^ missing tokens in macro arguments @@ -8,7 +8,7 @@ note: while trying to match `,` --> $SRC_DIR/core/src/mem/mod.rs:LL:COL error: unexpected end of macro invocation - --> $DIR/offset-of-arg-count.rs:7:45 + --> $DIR/offset-of-arg-count.rs:5:45 | LL | offset_of!(NotEnoughArgumentsWithAComma, ); | ^ missing tokens in macro arguments @@ -17,7 +17,7 @@ note: while trying to match meta-variable `$fields:expr` --> $SRC_DIR/core/src/mem/mod.rs:LL:COL error: no rules expected the token `too` - --> $DIR/offset-of-arg-count.rs:8:34 + --> $DIR/offset-of-arg-count.rs:6:34 | LL | offset_of!(Container, field, too many arguments); | ^^^ no rules expected this token in macro call @@ -25,25 +25,25 @@ LL | offset_of!(Container, field, too many arguments); = note: while trying to match sequence end error: unexpected token: `)` - --> $DIR/offset-of-arg-count.rs:11:21 + --> $DIR/offset-of-arg-count.rs:9:21 | LL | offset_of!(S, f.); | ^ error: unexpected token: `,` - --> $DIR/offset-of-arg-count.rs:12:21 + --> $DIR/offset-of-arg-count.rs:10:21 | LL | offset_of!(S, f.,); | ^ error: offset_of expects dot-separated field and variant names - --> $DIR/offset-of-arg-count.rs:13:19 + --> $DIR/offset-of-arg-count.rs:11:19 | LL | offset_of!(S, f..); | ^^^ error: offset_of expects dot-separated field and variant names - --> $DIR/offset-of-arg-count.rs:14:19 + --> $DIR/offset-of-arg-count.rs:12:19 | LL | offset_of!(S, f..,); | ^^^ diff --git a/tests/ui/offset-of/offset-of-dst-field.rs b/tests/ui/offset-of/offset-of-dst-field.rs index e393b159e64..016ebfadd14 100644 --- a/tests/ui/offset-of/offset-of-dst-field.rs +++ b/tests/ui/offset-of/offset-of-dst-field.rs @@ -1,4 +1,4 @@ -#![feature(offset_of, extern_types)] +#![feature(extern_types)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-enum.rs b/tests/ui/offset-of/offset-of-enum.rs index a2d6aace47d..cb2f04786ac 100644 --- a/tests/ui/offset-of/offset-of-enum.rs +++ b/tests/ui/offset-of/offset-of-enum.rs @@ -1,4 +1,4 @@ -#![feature(offset_of, offset_of_enum)] +#![feature(offset_of_enum, offset_of_nested)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-inference.rs b/tests/ui/offset-of/offset-of-inference.rs index ba87574eae0..1b1ae25e1ee 100644 --- a/tests/ui/offset-of/offset-of-inference.rs +++ b/tests/ui/offset-of/offset-of-inference.rs @@ -1,7 +1,5 @@ // Test that inference types in `offset_of!` don't ICE. -#![feature(offset_of)] - struct Foo { x: T, } diff --git a/tests/ui/offset-of/offset-of-inference.stderr b/tests/ui/offset-of/offset-of-inference.stderr index 1845822f11d..8bd104ed7e2 100644 --- a/tests/ui/offset-of/offset-of-inference.stderr +++ b/tests/ui/offset-of/offset-of-inference.stderr @@ -1,5 +1,5 @@ error[E0282]: type annotations needed - --> $DIR/offset-of-inference.rs:10:35 + --> $DIR/offset-of-inference.rs:8:35 | LL | let _ = core::mem::offset_of!(Foo<_>, x); | ^^^^^^ cannot infer type diff --git a/tests/ui/offset-of/offset-of-must-use.rs b/tests/ui/offset-of/offset-of-must-use.rs index e30145d7a2f..e4b092fcedf 100644 --- a/tests/ui/offset-of/offset-of-must-use.rs +++ b/tests/ui/offset-of/offset-of-must-use.rs @@ -1,6 +1,5 @@ // check-pass -#![feature(offset_of)] #![warn(unused)] fn main() { diff --git a/tests/ui/offset-of/offset-of-must-use.stderr b/tests/ui/offset-of/offset-of-must-use.stderr index 5fe387a7255..b6d88e098d0 100644 --- a/tests/ui/offset-of/offset-of-must-use.stderr +++ b/tests/ui/offset-of/offset-of-must-use.stderr @@ -1,11 +1,11 @@ warning: unused return value of `must_use` that must be used - --> $DIR/offset-of-must-use.rs:7:5 + --> $DIR/offset-of-must-use.rs:6:5 | LL | core::mem::offset_of!((String,), 0); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: the lint level is defined here - --> $DIR/offset-of-must-use.rs:4:9 + --> $DIR/offset-of-must-use.rs:3:9 | LL | #![warn(unused)] | ^^^^^^ diff --git a/tests/ui/offset-of/offset-of-output-type.rs b/tests/ui/offset-of/offset-of-output-type.rs index 50c2e93841f..76a33154ba3 100644 --- a/tests/ui/offset-of/offset-of-output-type.rs +++ b/tests/ui/offset-of/offset-of-output-type.rs @@ -1,5 +1,3 @@ -#![feature(offset_of)] - use std::mem::offset_of; struct S { diff --git a/tests/ui/offset-of/offset-of-output-type.stderr b/tests/ui/offset-of/offset-of-output-type.stderr index 233d4987643..34ad931d0ca 100644 --- a/tests/ui/offset-of/offset-of-output-type.stderr +++ b/tests/ui/offset-of/offset-of-output-type.stderr @@ -1,5 +1,5 @@ error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:12:17 + --> $DIR/offset-of-output-type.rs:10:17 | LL | let _: u8 = offset_of!(S, v); | ^^^^^^^^^^^^^^^^ expected `u8`, found `usize` @@ -7,7 +7,7 @@ LL | let _: u8 = offset_of!(S, v); = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:13:18 + --> $DIR/offset-of-output-type.rs:11:18 | LL | let _: u16 = offset_of!(S, v); | ^^^^^^^^^^^^^^^^ expected `u16`, found `usize` @@ -15,7 +15,7 @@ LL | let _: u16 = offset_of!(S, v); = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:14:18 + --> $DIR/offset-of-output-type.rs:12:18 | LL | let _: u32 = offset_of!(S, v); | ^^^^^^^^^^^^^^^^ expected `u32`, found `usize` @@ -23,7 +23,7 @@ LL | let _: u32 = offset_of!(S, v); = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:15:18 + --> $DIR/offset-of-output-type.rs:13:18 | LL | let _: u64 = offset_of!(S, v); | ^^^^^^^^^^^^^^^^ expected `u64`, found `usize` @@ -31,7 +31,7 @@ LL | let _: u64 = offset_of!(S, v); = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:16:20 + --> $DIR/offset-of-output-type.rs:14:20 | LL | let _: isize = offset_of!(S, v); | ^^^^^^^^^^^^^^^^ expected `isize`, found `usize` @@ -39,7 +39,7 @@ LL | let _: isize = offset_of!(S, v); = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info) error[E0308]: mismatched types - --> $DIR/offset-of-output-type.rs:19:5 + --> $DIR/offset-of-output-type.rs:17:5 | LL | fn main() { | - expected `()` because of default return type diff --git a/tests/ui/offset-of/offset-of-private.rs b/tests/ui/offset-of/offset-of-private.rs index b7affdb7943..1c326b5c79a 100644 --- a/tests/ui/offset-of/offset-of-private.rs +++ b/tests/ui/offset-of/offset-of-private.rs @@ -1,4 +1,4 @@ -#![feature(offset_of, offset_of_enum)] +#![feature(offset_of_enum, offset_of_nested)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-self.rs b/tests/ui/offset-of/offset-of-self.rs index 04dcaf7c0a6..1558e13b530 100644 --- a/tests/ui/offset-of/offset-of-self.rs +++ b/tests/ui/offset-of/offset-of-self.rs @@ -1,4 +1,4 @@ -#![feature(offset_of)] +#![feature(offset_of_nested)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-tuple-nested.rs b/tests/ui/offset-of/offset-of-tuple-nested.rs index 59b02e3c5c4..212176b2427 100644 --- a/tests/ui/offset-of/offset-of-tuple-nested.rs +++ b/tests/ui/offset-of/offset-of-tuple-nested.rs @@ -2,7 +2,7 @@ // Test for issue #112204 -- make sure this goes through the entire compilation pipeline, // similar to why `offset-of-unsized.rs` is also build-pass -#![feature(offset_of)] +#![feature(offset_of_nested)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-tuple.rs b/tests/ui/offset-of/offset-of-tuple.rs index b6fc1e32229..75ba8d77f2f 100644 --- a/tests/ui/offset-of/offset-of-tuple.rs +++ b/tests/ui/offset-of/offset-of-tuple.rs @@ -1,4 +1,4 @@ -#![feature(offset_of)] +#![feature(offset_of_nested)] #![feature(builtin_syntax)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-unsized.rs b/tests/ui/offset-of/offset-of-unsized.rs index 49c8328da5c..b70529ed7b8 100644 --- a/tests/ui/offset-of/offset-of-unsized.rs +++ b/tests/ui/offset-of/offset-of-unsized.rs @@ -2,8 +2,6 @@ // regression test for #112051, not in `offset-of-dst` as the issue is in codegen, // and isn't triggered in the presence of typeck errors -#![feature(offset_of)] - struct S { a: u64, b: T, diff --git a/tests/ui/offset-of/offset-of-unstable-with-feature.rs b/tests/ui/offset-of/offset-of-unstable-with-feature.rs index 7d2eb46c056..be275564a0a 100644 --- a/tests/ui/offset-of/offset-of-unstable-with-feature.rs +++ b/tests/ui/offset-of/offset-of-unstable-with-feature.rs @@ -1,7 +1,7 @@ // check-pass // aux-build:offset-of-staged-api.rs -#![feature(offset_of, unstable_test_feature)] +#![feature(offset_of_nested, unstable_test_feature)] use std::mem::offset_of; diff --git a/tests/ui/offset-of/offset-of-unstable.rs b/tests/ui/offset-of/offset-of-unstable.rs index 1e19f2091f2..da0882abd22 100644 --- a/tests/ui/offset-of/offset-of-unstable.rs +++ b/tests/ui/offset-of/offset-of-unstable.rs @@ -1,6 +1,6 @@ // aux-build:offset-of-staged-api.rs -#![feature(offset_of)] +#![feature(offset_of_nested)] use std::mem::offset_of;