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Merge pull request #115 from bluss/merge-0.4
Merge 0.4 branch to master
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
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| use std::env; | ||
| use std::io::Write; | ||
| use std::process::{Command, Stdio}; | ||
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| fn main() { | ||
| // we need to output *some* file to opt out of the default | ||
| println!("cargo:rerun-if-changed=build.rs"); | ||
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| detect_maybe_uninit(); | ||
| } | ||
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| fn detect_maybe_uninit() { | ||
| let has_unstable_union_with_md = probe(&maybe_uninit_code(true)); | ||
| if has_unstable_union_with_md { | ||
| println!("cargo:rustc-cfg=has_manually_drop_in_union"); | ||
| println!("cargo:rustc-cfg=has_union_feature"); | ||
| return; | ||
| } | ||
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| let has_stable_union_with_md = probe(&maybe_uninit_code(false)); | ||
| if has_stable_union_with_md { | ||
| println!("cargo:rustc-cfg=has_manually_drop_in_union"); | ||
| } | ||
| } | ||
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| // To guard against changes in this currently unstable feature, use | ||
| // a detection tests instead of a Rustc version and/or date test. | ||
| fn maybe_uninit_code(use_feature: bool) -> String { | ||
| let feature = if use_feature { "#![feature(untagged_unions)]" } else { "" }; | ||
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| let code = " | ||
| #![allow(warnings)] | ||
| use std::mem::ManuallyDrop; | ||
| #[derive(Copy)] | ||
| pub union MaybeUninit<T> { | ||
| empty: (), | ||
| value: ManuallyDrop<T>, | ||
| } | ||
| impl<T> Clone for MaybeUninit<T> where T: Copy | ||
| { | ||
| fn clone(&self) -> Self { *self } | ||
| } | ||
| fn main() { | ||
| let value1 = MaybeUninit::<[i32; 3]> { empty: () }; | ||
| let value2 = MaybeUninit { value: ManuallyDrop::new([1, 2, 3]) }; | ||
| } | ||
| "; | ||
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| [feature, code].concat() | ||
| } | ||
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| /// Test if a code snippet can be compiled | ||
| fn probe(code: &str) -> bool { | ||
| let rustc = env::var_os("RUSTC").unwrap_or_else(|| "rustc".into()); | ||
| let out_dir = env::var_os("OUT_DIR").expect("environment variable OUT_DIR"); | ||
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| let mut child = Command::new(rustc) | ||
| .arg("--out-dir") | ||
| .arg(out_dir) | ||
| .arg("--emit=obj") | ||
| .arg("-") | ||
| .stdin(Stdio::piped()) | ||
| .spawn() | ||
| .expect("rustc probe"); | ||
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| child | ||
| .stdin | ||
| .as_mut() | ||
| .expect("rustc stdin") | ||
| .write_all(code.as_bytes()) | ||
| .expect("write rustc stdin"); | ||
|
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| child.wait().expect("rustc probe").success() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,51 @@ | ||
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| use array::Array; | ||
| use std::mem::ManuallyDrop; | ||
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| /// A combination of ManuallyDrop and “maybe uninitialized”; | ||
| /// this wraps a value that can be wholly or partially uninitialized; | ||
| /// it also has no drop regardless of the type of T. | ||
| #[derive(Copy)] | ||
| pub union MaybeUninit<T> { | ||
| empty: (), | ||
| value: ManuallyDrop<T>, | ||
| } | ||
| // Why we don't use std's MaybeUninit on nightly? See the ptr method | ||
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| impl<T> Clone for MaybeUninit<T> where T: Copy | ||
| { | ||
| fn clone(&self) -> Self { *self } | ||
| } | ||
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| impl<T> MaybeUninit<T> { | ||
| /// Create a new MaybeUninit with uninitialized interior | ||
| pub unsafe fn uninitialized() -> Self { | ||
| MaybeUninit { empty: () } | ||
| } | ||
|
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| /// Create a new MaybeUninit from the value `v`. | ||
| pub fn from(v: T) -> Self { | ||
| MaybeUninit { value: ManuallyDrop::new(v) } | ||
| } | ||
|
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||
| // Raw pointer casts written so that we don't reference or access the | ||
| // uninitialized interior value | ||
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| /// Return a raw pointer to the start of the interior array | ||
| pub fn ptr(&self) -> *const T::Item | ||
| where T: Array | ||
| { | ||
| // std MaybeUninit creates a &self.value reference here which is | ||
| // not guaranteed to be sound in our case - we will partially | ||
| // initialize the value, not always wholly. | ||
| self as *const _ as *const T::Item | ||
| } | ||
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| /// Return a mut raw pointer to the start of the interior array | ||
| pub fn ptr_mut(&mut self) -> *mut T::Item | ||
| where T: Array | ||
| { | ||
| self as *mut _ as *mut T::Item | ||
| } | ||
| } |
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