platforms 3.3.0

Rust platform registry with information about valid Rust platforms (target triple, target_arch, target_os) sourced from the Rust compiler.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

//! Rust platforms

mod platforms;

#[cfg(feature = "std")]
mod req;
mod tier;

pub use self::tier::Tier;

#[cfg(feature = "std")]
pub use self::req::PlatformReq;

use self::platforms::ALL;
use crate::target::*;
use core::fmt;

/// Rust platforms supported by mainline rustc
///
/// Sourced from <https://doc.rust-lang.org/nightly/rustc/platform-support.html>
/// as well as the latest nightly version of `rustc`
#[derive(Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
#[non_exhaustive]
pub struct Platform {
    /// "Target triple" string uniquely identifying the platform. See:
    /// <https://github.com/rust-lang/rfcs/blob/master/text/0131-target-specification.md>
    ///
    /// These are defined in the `rustc_target` crate of the Rust compiler:
    /// <https://github.com/rust-lang/rust/blob/master/src/librustc_target/spec/mod.rs>
    pub target_triple: &'static str,

    /// Target architecture `cfg` attribute (i.e. `cfg(target_arch)`)
    pub target_arch: Arch,

    /// Target OS `cfg` attribute (i.e. `cfg(target_os)`).
    pub target_os: OS,

    /// Target environment `cfg` attribute (i.e. `cfg(target_env)`).
    /// Only used when needed for disambiguation, e.g. on many GNU platforms
    /// this value will be `None`.
    pub target_env: Env,

    /// Target pointer width `cfg` attribute, in bits (i.e. `cfg(target_pointer_width)`).
    /// Typically 64 on modern platforms, 32 on older platforms, 16 on some microcontrollers.
    pub target_pointer_width: PointerWidth,

    /// Target [endianness](https://en.wikipedia.org/wiki/Endianness) `cfg` attribute (i.e. `cfg(target_endian)`).
    /// Set to "little" on the vast majority of modern platforms.
    pub target_endian: Endian,

    /// Tier of this platform:
    ///
    /// - `Tier::One`: guaranteed to work
    /// - `Tier::Two`: guaranteed to build
    /// - `Tier::Three`: unofficially supported with no guarantees
    pub tier: Tier,
}

impl Platform {
    /// All valid Rust platforms usable from the mainline compiler.
    ///
    /// Note that this list will evolve over time, and platforms will be both added and removed.
    pub const ALL: &'static [Platform] = ALL;

    /// Find a Rust platform by its "target triple", e.g. `i686-apple-darwin`
    pub fn find(target_triple: &str) -> Option<&'static Platform> {
        Self::ALL
            .iter()
            .find(|platform| platform.target_triple == target_triple)
    }
}

impl fmt::Display for Platform {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.target_triple)
    }
}

#[cfg(all(test, feature = "std"))]
mod tests {
    use super::Platform;
    use std::collections::HashSet;

    /// Ensure there are no duplicate target triples in the platforms list
    #[test]
    fn no_dupes_test() {
        let mut target_triples = HashSet::new();

        for platform in Platform::ALL {
            assert!(
                target_triples.insert(platform.target_triple),
                "duplicate target triple: {}",
                platform.target_triple
            );
        }
    }

    use std::collections::HashMap;

    use super::*;

    /// `platforms` v2.0 used to provide various constants passed as `cfg` values,
    /// and attempted to detect the target triple based on that.
    /// This test is meant to check whether such detection can be accurate.
    ///
    /// Turns out that as of v3.0 this is infeasible,
    /// even though the list of supported cfg values was expanded.
    ///
    /// I have also verified that no possible expansion of the supported cfg fields
    /// will lets uniquely identify the platform based on cfg values using a shell script:
    /// `rustc --print=target-list | parallel 'rustc --print=cfg --target={} > ./{}'; fdupes`
    #[test]
    #[ignore]
    fn test_detection_feasibility() {
        let mut all_platforms = HashMap::new();
        for p in ALL {
            if let Some(other_p) = all_platforms.insert(
                (
                    p.target_arch,
                    p.target_os,
                    p.target_env,
                    p.target_endian,
                    p.target_pointer_width,
                ),
                p.target_triple,
            ) {
                panic!("{} and {} have identical properties, and cannot be distinguished based on properties alone", p.target_triple, other_p);
            }
        }
    }
}