Auto merge of #46123 - Gankro:c-repr, r=eddyb
Implement the special repr(C)-non-clike-enum layout This is the second half of https://github.com/rust-lang/rfcs/pull/2195 which specifies that ```rust #[repr(C, u8)] #[derive(Copy, Clone, Eq, PartialEq, Debug)] enum MyEnum { A(u32), // Single primitive value B { x: u8, y: i16 }, // Composite, and the offset of `y` depends on tag being internal C, // Empty D(Option<u32>), // Contains an enum E(Duration), // Contains a struct } ``` Has the same layout as ```rust #[repr(C)] struct MyEnumRepr { tag: MyEnumTag, payload: MyEnumPayload, } #[repr(C)] #[allow(non_snake_case)] union MyEnumPayload { A: MyEnumVariantA, B: MyEnumVariantB, D: MyEnumVariantD, E: MyEnumVariantE, } #[repr(u8)] #[derive(Copy, Clone)] enum MyEnumTag { A, B, C, D, E } #[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantA(u32); #[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantB {x: u8, y: i16 } #[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantD(Option<u32>); #[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantE(Duration); ```
This commit is contained in:
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commit
436ac8928a
@ -75,7 +75,9 @@ impl<'a> CheckAttrVisitor<'a> {
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}
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};
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let mut conflicting_reprs = 0;
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let mut int_reprs = 0;
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let mut is_c = false;
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let mut is_simd = false;
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for word in words {
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@ -86,7 +88,7 @@ impl<'a> CheckAttrVisitor<'a> {
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let (message, label) = match &*name.as_str() {
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"C" => {
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conflicting_reprs += 1;
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is_c = true;
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if target != Target::Struct &&
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target != Target::Union &&
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target != Target::Enum {
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@ -108,7 +110,7 @@ impl<'a> CheckAttrVisitor<'a> {
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}
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}
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"simd" => {
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conflicting_reprs += 1;
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is_simd = true;
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if target != Target::Struct {
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("attribute should be applied to struct",
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"a struct")
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@ -128,7 +130,7 @@ impl<'a> CheckAttrVisitor<'a> {
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"i8" | "u8" | "i16" | "u16" |
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"i32" | "u32" | "i64" | "u64" |
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"isize" | "usize" => {
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conflicting_reprs += 1;
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int_reprs += 1;
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if target != Target::Enum {
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("attribute should be applied to enum",
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"an enum")
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@ -142,7 +144,11 @@ impl<'a> CheckAttrVisitor<'a> {
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.span_label(item.span, format!("not {}", label))
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.emit();
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}
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if conflicting_reprs > 1 {
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// Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
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if (int_reprs > 1)
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|| (is_simd && is_c)
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|| (int_reprs == 1 && is_c && is_c_like_enum(item)) {
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span_warn!(self.sess, attr.span, E0566,
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"conflicting representation hints");
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}
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@ -162,3 +168,17 @@ impl<'a> Visitor<'a> for CheckAttrVisitor<'a> {
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pub fn check_crate(sess: &Session, krate: &ast::Crate) {
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visit::walk_crate(&mut CheckAttrVisitor { sess: sess }, krate);
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}
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fn is_c_like_enum(item: &ast::Item) -> bool {
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if let ast::ItemKind::Enum(ref def, _) = item.node {
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for variant in &def.variants {
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match variant.node.data {
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ast::VariantData::Unit(_) => { /* continue */ }
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_ => { return false; }
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}
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}
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true
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} else {
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false
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}
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}
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@ -942,8 +942,8 @@ impl<'a, 'tcx> LayoutDetails {
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AlwaysSized,
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/// A univariant, the last field of which may be coerced to unsized.
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MaybeUnsized,
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/// A univariant, but part of an enum.
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EnumVariant(Integer),
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/// A univariant, but with a prefix of an arbitrary size & alignment (e.g. enum tag).
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Prefixed(Size, Align),
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}
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let univariant_uninterned = |fields: &[TyLayout], repr: &ReprOptions, kind| {
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let packed = repr.packed();
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@ -962,14 +962,11 @@ impl<'a, 'tcx> LayoutDetails {
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let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
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// Anything with repr(C) or repr(packed) doesn't optimize.
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let optimize = match kind {
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StructKind::AlwaysSized |
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StructKind::MaybeUnsized |
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StructKind::EnumVariant(I8) => {
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(repr.flags & ReprFlags::IS_UNOPTIMISABLE).is_empty()
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let mut optimize = (repr.flags & ReprFlags::IS_UNOPTIMISABLE).is_empty();
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if let StructKind::Prefixed(_, align) = kind {
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optimize &= align.abi() == 1;
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}
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StructKind::EnumVariant(_) => false
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};
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if optimize {
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let end = if let StructKind::MaybeUnsized = kind {
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fields.len() - 1
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@ -987,7 +984,7 @@ impl<'a, 'tcx> LayoutDetails {
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(!f.is_zst(), cmp::Reverse(f.align.abi()))
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})
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}
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StructKind::EnumVariant(_) => {
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StructKind::Prefixed(..) => {
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optimizing.sort_by_key(|&x| fields[x as usize].align.abi());
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}
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}
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@ -1001,12 +998,11 @@ impl<'a, 'tcx> LayoutDetails {
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let mut offset = Size::from_bytes(0);
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if let StructKind::EnumVariant(discr) = kind {
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offset = discr.size();
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if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
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if !packed {
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let discr_align = discr.align(dl);
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align = align.max(discr_align);
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align = align.max(prefix_align);
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}
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offset = prefix_size.abi_align(prefix_align);
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}
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for &i in &inverse_memory_index {
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@ -1558,10 +1554,24 @@ impl<'a, 'tcx> LayoutDetails {
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let mut start_align = Align::from_bytes(256, 256).unwrap();
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assert_eq!(Integer::for_abi_align(dl, start_align), None);
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// repr(C) on an enum tells us to make a (tag, union) layout,
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// so we need to grow the prefix alignment to be at least
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// the alignment of the union. (This value is used both for
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// determining the alignment of the overall enum, and the
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// determining the alignment of the payload after the tag.)
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let mut prefix_align = min_ity.align(dl);
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if def.repr.c() {
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for fields in &variants {
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for field in fields {
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prefix_align = prefix_align.max(field.align);
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}
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}
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}
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// Create the set of structs that represent each variant.
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let mut variants = variants.into_iter().enumerate().map(|(i, field_layouts)| {
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let mut st = univariant_uninterned(&field_layouts,
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&def.repr, StructKind::EnumVariant(min_ity))?;
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&def.repr, StructKind::Prefixed(min_ity.size(), prefix_align))?;
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st.variants = Variants::Single { index: i };
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// Find the first field we can't move later
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// to make room for a larger discriminant.
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177
src/test/run-pass/enum-non-c-like-repr-c-and-int.rs
Normal file
177
src/test/run-pass/enum-non-c-like-repr-c-and-int.rs
Normal file
@ -0,0 +1,177 @@
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// This test deserializes an enum in-place by transmuting to a union that
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// should have the same layout, and manipulating the tag and payloads
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// independently. This verifies that `repr(some_int)` has a stable representation,
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// and that we don't miscompile these kinds of manipulations.
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use std::time::Duration;
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use std::mem;
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#[repr(C, u8)]
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#[derive(Copy, Clone, Eq, PartialEq, Debug)]
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enum MyEnum {
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A(u32), // Single primitive value
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B { x: u8, y: i16 }, // Composite, and the offset of `y` depends on tag being internal
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C, // Empty
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D(Option<u32>), // Contains an enum
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E(Duration), // Contains a struct
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}
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#[repr(C)]
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struct MyEnumRepr {
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tag: MyEnumTag,
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payload: MyEnumPayload,
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}
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#[repr(C)]
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#[allow(non_snake_case)]
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union MyEnumPayload {
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A: MyEnumVariantA,
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B: MyEnumVariantB,
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D: MyEnumVariantD,
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E: MyEnumVariantE,
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}
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#[repr(u8)] #[derive(Copy, Clone)] enum MyEnumTag { A, B, C, D, E }
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantA(u32);
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantB {x: u8, y: i16 }
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantD(Option<u32>);
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantE(Duration);
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fn main() {
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let result: Vec<Result<MyEnum, ()>> = vec![
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Ok(MyEnum::A(17)),
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Ok(MyEnum::B { x: 206, y: 1145 }),
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Ok(MyEnum::C),
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Err(()),
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Ok(MyEnum::D(Some(407))),
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Ok(MyEnum::D(None)),
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Ok(MyEnum::E(Duration::from_secs(100))),
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Err(()),
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];
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// Binary serialized version of the above (little-endian)
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let input: Vec<u8> = vec![
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0, 17, 0, 0, 0,
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1, 206, 121, 4,
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2,
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8, /* invalid tag value */
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3, 0, 151, 1, 0, 0,
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3, 1,
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4, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, /* incomplete value */
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];
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let mut output = vec![];
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let mut buf = &input[..];
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unsafe {
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// This should be safe, because we don't match on it unless it's fully formed,
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// and it doesn't have a destructor.
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let mut dest: MyEnum = mem::uninitialized();
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while buf.len() > 0 {
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match parse_my_enum(&mut dest, &mut buf) {
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Ok(()) => output.push(Ok(dest)),
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Err(()) => output.push(Err(())),
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}
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}
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}
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assert_eq!(output, result);
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}
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fn parse_my_enum<'a>(dest: &'a mut MyEnum, buf: &mut &[u8]) -> Result<(), ()> {
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unsafe {
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// Should be correct to do this transmute.
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let dest: &'a mut MyEnumRepr = mem::transmute(dest);
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let tag = read_u8(buf)?;
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dest.tag = match tag {
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0 => MyEnumTag::A,
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1 => MyEnumTag::B,
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2 => MyEnumTag::C,
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3 => MyEnumTag::D,
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4 => MyEnumTag::E,
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_ => return Err(()),
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};
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match dest.tag {
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MyEnumTag::A => {
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dest.payload.A.0 = read_u32_le(buf)?;
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}
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MyEnumTag::B => {
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dest.payload.B.x = read_u8(buf)?;
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dest.payload.B.y = read_u16_le(buf)? as i16;
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}
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MyEnumTag::C => {
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/* do nothing */
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}
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MyEnumTag::D => {
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let is_some = read_u8(buf)? == 0;
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if is_some {
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dest.payload.D.0 = Some(read_u32_le(buf)?);
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} else {
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dest.payload.D.0 = None;
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}
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}
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MyEnumTag::E => {
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let secs = read_u64_le(buf)?;
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let nanos = read_u32_le(buf)?;
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dest.payload.E.0 = Duration::new(secs, nanos);
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}
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}
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Ok(())
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}
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}
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// reader helpers
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fn read_u64_le(buf: &mut &[u8]) -> Result<u64, ()> {
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if buf.len() < 8 { return Err(()) }
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let val = (buf[0] as u64) << 0
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| (buf[1] as u64) << 8
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| (buf[2] as u64) << 16
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| (buf[3] as u64) << 24
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| (buf[4] as u64) << 32
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| (buf[5] as u64) << 40
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| (buf[6] as u64) << 48
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| (buf[7] as u64) << 56;
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*buf = &buf[8..];
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Ok(val)
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}
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fn read_u32_le(buf: &mut &[u8]) -> Result<u32, ()> {
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if buf.len() < 4 { return Err(()) }
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let val = (buf[0] as u32) << 0
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| (buf[1] as u32) << 8
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| (buf[2] as u32) << 16
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| (buf[3] as u32) << 24;
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*buf = &buf[4..];
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Ok(val)
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}
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fn read_u16_le(buf: &mut &[u8]) -> Result<u16, ()> {
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if buf.len() < 2 { return Err(()) }
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let val = (buf[0] as u16) << 0
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| (buf[1] as u16) << 8;
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*buf = &buf[2..];
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Ok(val)
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}
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fn read_u8(buf: &mut &[u8]) -> Result<u8, ()> {
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if buf.len() < 1 { return Err(()) }
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let val = buf[0];
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*buf = &buf[1..];
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Ok(val)
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}
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177
src/test/run-pass/enum-non-c-like-repr-c.rs
Normal file
177
src/test/run-pass/enum-non-c-like-repr-c.rs
Normal file
@ -0,0 +1,177 @@
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
|
||||
// file at the top-level directory of this distribution and at
|
||||
// http://rust-lang.org/COPYRIGHT.
|
||||
//
|
||||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
||||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
||||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
||||
// option. This file may not be copied, modified, or distributed
|
||||
// except according to those terms.
|
||||
|
||||
// This test deserializes an enum in-place by transmuting to a union that
|
||||
// should have the same layout, and manipulating the tag and payloads
|
||||
// independently. This verifies that `repr(some_int)` has a stable representation,
|
||||
// and that we don't miscompile these kinds of manipulations.
|
||||
|
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use std::time::Duration;
|
||||
use std::mem;
|
||||
|
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#[repr(C)]
|
||||
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
|
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enum MyEnum {
|
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A(u32), // Single primitive value
|
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B { x: u8, y: i16 }, // Composite, and the offset of `y` depends on tag being internal
|
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C, // Empty
|
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D(Option<u32>), // Contains an enum
|
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E(Duration), // Contains a struct
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}
|
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|
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#[repr(C)]
|
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struct MyEnumRepr {
|
||||
tag: MyEnumTag,
|
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payload: MyEnumPayload,
|
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}
|
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|
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#[repr(C)]
|
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#[allow(non_snake_case)]
|
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union MyEnumPayload {
|
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A: MyEnumVariantA,
|
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B: MyEnumVariantB,
|
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D: MyEnumVariantD,
|
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E: MyEnumVariantE,
|
||||
}
|
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|
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#[repr(C)] #[derive(Copy, Clone)] enum MyEnumTag { A, B, C, D, E }
|
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantA(u32);
|
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantB {x: u8, y: i16 }
|
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#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantD(Option<u32>);
|
||||
#[repr(C)] #[derive(Copy, Clone)] struct MyEnumVariantE(Duration);
|
||||
|
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fn main() {
|
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let result: Vec<Result<MyEnum, ()>> = vec![
|
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Ok(MyEnum::A(17)),
|
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Ok(MyEnum::B { x: 206, y: 1145 }),
|
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Ok(MyEnum::C),
|
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Err(()),
|
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Ok(MyEnum::D(Some(407))),
|
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Ok(MyEnum::D(None)),
|
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Ok(MyEnum::E(Duration::from_secs(100))),
|
||||
Err(()),
|
||||
];
|
||||
|
||||
// Binary serialized version of the above (little-endian)
|
||||
let input: Vec<u8> = vec![
|
||||
0, 17, 0, 0, 0,
|
||||
1, 206, 121, 4,
|
||||
2,
|
||||
8, /* invalid tag value */
|
||||
3, 0, 151, 1, 0, 0,
|
||||
3, 1,
|
||||
4, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
|
||||
0, /* incomplete value */
|
||||
];
|
||||
|
||||
let mut output = vec![];
|
||||
let mut buf = &input[..];
|
||||
|
||||
unsafe {
|
||||
// This should be safe, because we don't match on it unless it's fully formed,
|
||||
// and it doesn't have a destructor.
|
||||
let mut dest: MyEnum = mem::uninitialized();
|
||||
while buf.len() > 0 {
|
||||
match parse_my_enum(&mut dest, &mut buf) {
|
||||
Ok(()) => output.push(Ok(dest)),
|
||||
Err(()) => output.push(Err(())),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
assert_eq!(output, result);
|
||||
}
|
||||
|
||||
fn parse_my_enum<'a>(dest: &'a mut MyEnum, buf: &mut &[u8]) -> Result<(), ()> {
|
||||
unsafe {
|
||||
// Should be correct to do this transmute.
|
||||
let dest: &'a mut MyEnumRepr = mem::transmute(dest);
|
||||
let tag = read_u8(buf)?;
|
||||
|
||||
dest.tag = match tag {
|
||||
0 => MyEnumTag::A,
|
||||
1 => MyEnumTag::B,
|
||||
2 => MyEnumTag::C,
|
||||
3 => MyEnumTag::D,
|
||||
4 => MyEnumTag::E,
|
||||
_ => return Err(()),
|
||||
};
|
||||
|
||||
match dest.tag {
|
||||
MyEnumTag::A => {
|
||||
dest.payload.A.0 = read_u32_le(buf)?;
|
||||
}
|
||||
MyEnumTag::B => {
|
||||
dest.payload.B.x = read_u8(buf)?;
|
||||
dest.payload.B.y = read_u16_le(buf)? as i16;
|
||||
}
|
||||
MyEnumTag::C => {
|
||||
/* do nothing */
|
||||
}
|
||||
MyEnumTag::D => {
|
||||
let is_some = read_u8(buf)? == 0;
|
||||
if is_some {
|
||||
dest.payload.D.0 = Some(read_u32_le(buf)?);
|
||||
} else {
|
||||
dest.payload.D.0 = None;
|
||||
}
|
||||
}
|
||||
MyEnumTag::E => {
|
||||
let secs = read_u64_le(buf)?;
|
||||
let nanos = read_u32_le(buf)?;
|
||||
dest.payload.E.0 = Duration::new(secs, nanos);
|
||||
}
|
||||
}
|
||||
Ok(())
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
|
||||
// reader helpers
|
||||
|
||||
fn read_u64_le(buf: &mut &[u8]) -> Result<u64, ()> {
|
||||
if buf.len() < 8 { return Err(()) }
|
||||
let val = (buf[0] as u64) << 0
|
||||
| (buf[1] as u64) << 8
|
||||
| (buf[2] as u64) << 16
|
||||
| (buf[3] as u64) << 24
|
||||
| (buf[4] as u64) << 32
|
||||
| (buf[5] as u64) << 40
|
||||
| (buf[6] as u64) << 48
|
||||
| (buf[7] as u64) << 56;
|
||||
*buf = &buf[8..];
|
||||
Ok(val)
|
||||
}
|
||||
|
||||
fn read_u32_le(buf: &mut &[u8]) -> Result<u32, ()> {
|
||||
if buf.len() < 4 { return Err(()) }
|
||||
let val = (buf[0] as u32) << 0
|
||||
| (buf[1] as u32) << 8
|
||||
| (buf[2] as u32) << 16
|
||||
| (buf[3] as u32) << 24;
|
||||
*buf = &buf[4..];
|
||||
Ok(val)
|
||||
}
|
||||
|
||||
fn read_u16_le(buf: &mut &[u8]) -> Result<u16, ()> {
|
||||
if buf.len() < 2 { return Err(()) }
|
||||
let val = (buf[0] as u16) << 0
|
||||
| (buf[1] as u16) << 8;
|
||||
*buf = &buf[2..];
|
||||
Ok(val)
|
||||
}
|
||||
|
||||
fn read_u8(buf: &mut &[u8]) -> Result<u8, ()> {
|
||||
if buf.len() < 1 { return Err(()) }
|
||||
let val = buf[0];
|
||||
*buf = &buf[1..];
|
||||
Ok(val)
|
||||
}
|
||||
@ -9,7 +9,8 @@
|
||||
// except according to those terms.
|
||||
|
||||
|
||||
use std::mem::size_of;
|
||||
use std::mem::{size_of, align_of};
|
||||
use std::os::raw::c_int;
|
||||
|
||||
// The two enums that follow are designed so that bugs trigger layout optimization.
|
||||
// Specifically, if either of the following reprs used here is not detected by the compiler,
|
||||
@ -27,6 +28,38 @@ enum E2 {
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
// Check that repr(int) and repr(C) are in fact different from the above
|
||||
|
||||
#[repr(u8)]
|
||||
enum E3 {
|
||||
A(u8, u16, u8),
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
#[repr(u16)]
|
||||
enum E4 {
|
||||
A(u8, u16, u8),
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
#[repr(u32)]
|
||||
enum E5 {
|
||||
A(u8, u16, u8),
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
#[repr(u64)]
|
||||
enum E6 {
|
||||
A(u8, u16, u8),
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
#[repr(C)]
|
||||
enum E7 {
|
||||
A(u8, u16, u8),
|
||||
B(u8, u16, u8)
|
||||
}
|
||||
|
||||
// From pr 37429
|
||||
|
||||
#[repr(C,packed)]
|
||||
@ -37,7 +70,20 @@ pub struct p0f_api_query {
|
||||
}
|
||||
|
||||
pub fn main() {
|
||||
assert_eq!(size_of::<E1>(), 6);
|
||||
assert_eq!(size_of::<E2>(), 6);
|
||||
assert_eq!(size_of::<E1>(), 8);
|
||||
assert_eq!(size_of::<E2>(), 8);
|
||||
assert_eq!(size_of::<E3>(), 6);
|
||||
assert_eq!(size_of::<E4>(), 8);
|
||||
assert_eq!(size_of::<E5>(), align_size(10, align_of::<u32>()));
|
||||
assert_eq!(size_of::<E6>(), align_size(14, align_of::<u64>()));
|
||||
assert_eq!(size_of::<E7>(), align_size(6 + size_of::<c_int>(), align_of::<c_int>()));
|
||||
assert_eq!(size_of::<p0f_api_query>(), 21);
|
||||
}
|
||||
|
||||
fn align_size(size: usize, align: usize) -> usize {
|
||||
if size % align != 0 {
|
||||
size + (align - (size % align))
|
||||
} else {
|
||||
size
|
||||
}
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user