1 use std::env;
2 use std::process::Command;
3 use std::str::{self, FromStr};
4
5 // The rustc-cfg strings below are *not* public API. Please let us know by
6 // opening a GitHub issue if your build environment requires some way to enable
7 // these cfgs other than by executing our build script.
main()8 fn main() {
9 println!("cargo:rerun-if-changed=build.rs");
10
11 let minor = match rustc_minor_version() {
12 Some(minor) => minor,
13 None => return,
14 };
15
16 let target = env::var("TARGET").unwrap();
17 let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
18
19 // std::collections::Bound was stabilized in Rust 1.17
20 // but it was moved to core::ops later in Rust 1.26:
21 // https://doc.rust-lang.org/core/ops/enum.Bound.html
22 if minor < 26 {
23 println!("cargo:rustc-cfg=no_ops_bound");
24 if minor < 17 {
25 println!("cargo:rustc-cfg=no_collections_bound");
26 }
27 }
28
29 // core::cmp::Reverse stabilized in Rust 1.19:
30 // https://doc.rust-lang.org/stable/core/cmp/struct.Reverse.html
31 if minor < 19 {
32 println!("cargo:rustc-cfg=no_core_reverse");
33 }
34
35 // CString::into_boxed_c_str and PathBuf::into_boxed_path stabilized in Rust 1.20:
36 // https://doc.rust-lang.org/std/ffi/struct.CString.html#method.into_boxed_c_str
37 // https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.into_boxed_path
38 if minor < 20 {
39 println!("cargo:rustc-cfg=no_de_boxed_c_str");
40 println!("cargo:rustc-cfg=no_de_boxed_path");
41 }
42
43 // From<Box<T>> for Rc<T> / Arc<T> stabilized in Rust 1.21:
44 // https://doc.rust-lang.org/std/rc/struct.Rc.html#impl-From<Box<T>>
45 // https://doc.rust-lang.org/std/sync/struct.Arc.html#impl-From<Box<T>>
46 if minor < 21 {
47 println!("cargo:rustc-cfg=no_de_rc_dst");
48 }
49
50 // Duration available in core since Rust 1.25:
51 // https://blog.rust-lang.org/2018/03/29/Rust-1.25.html#library-stabilizations
52 if minor < 25 {
53 println!("cargo:rustc-cfg=no_core_duration");
54 }
55
56 // 128-bit integers stabilized in Rust 1.26:
57 // https://blog.rust-lang.org/2018/05/10/Rust-1.26.html
58 //
59 // Disabled on Emscripten targets before Rust 1.40 since
60 // Emscripten did not support 128-bit integers until Rust 1.40
61 // (https://github.com/rust-lang/rust/pull/65251)
62 if minor < 26 || emscripten && minor < 40 {
63 println!("cargo:rustc-cfg=no_integer128");
64 }
65
66 // Inclusive ranges methods stabilized in Rust 1.27:
67 // https://github.com/rust-lang/rust/pull/50758
68 // Also Iterator::try_for_each:
69 // https://blog.rust-lang.org/2018/06/21/Rust-1.27.html#library-stabilizations
70 if minor < 27 {
71 println!("cargo:rustc-cfg=no_range_inclusive");
72 println!("cargo:rustc-cfg=no_iterator_try_fold");
73 }
74
75 // Non-zero integers stabilized in Rust 1.28:
76 // https://blog.rust-lang.org/2018/08/02/Rust-1.28.html#library-stabilizations
77 if minor < 28 {
78 println!("cargo:rustc-cfg=no_num_nonzero");
79 }
80
81 // TryFrom, Atomic types, non-zero signed integers, and SystemTime::checked_add
82 // stabilized in Rust 1.34:
83 // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#tryfrom-and-tryinto
84 // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#library-stabilizations
85 if minor < 34 {
86 println!("cargo:rustc-cfg=no_core_try_from");
87 println!("cargo:rustc-cfg=no_num_nonzero_signed");
88 println!("cargo:rustc-cfg=no_systemtime_checked_add");
89 println!("cargo:rustc-cfg=no_relaxed_trait_bounds");
90 }
91
92 // Current minimum supported version of serde_derive crate is Rust 1.56.
93 if minor < 56 {
94 println!("cargo:rustc-cfg=no_serde_derive");
95 }
96
97 // Support for #[cfg(target_has_atomic = "...")] stabilized in Rust 1.60.
98 if minor < 60 {
99 println!("cargo:rustc-cfg=no_target_has_atomic");
100 // Allowlist of archs that support std::sync::atomic module. This is
101 // based on rustc's compiler/rustc_target/src/spec/*.rs.
102 let has_atomic64 = target.starts_with("x86_64")
103 || target.starts_with("i686")
104 || target.starts_with("aarch64")
105 || target.starts_with("powerpc64")
106 || target.starts_with("sparc64")
107 || target.starts_with("mips64el")
108 || target.starts_with("riscv64");
109 let has_atomic32 = has_atomic64 || emscripten;
110 if minor < 34 || !has_atomic64 {
111 println!("cargo:rustc-cfg=no_std_atomic64");
112 }
113 if minor < 34 || !has_atomic32 {
114 println!("cargo:rustc-cfg=no_std_atomic");
115 }
116 }
117
118 // Support for core::ffi::CStr and alloc::ffi::CString stabilized in Rust 1.64.
119 // https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html#c-compatible-ffi-types-in-core-and-alloc
120 if minor < 64 {
121 println!("cargo:rustc-cfg=no_core_cstr");
122 }
123 }
124
rustc_minor_version() -> Option<u32>125 fn rustc_minor_version() -> Option<u32> {
126 let rustc = match env::var_os("RUSTC") {
127 Some(rustc) => rustc,
128 None => return None,
129 };
130
131 let output = match Command::new(rustc).arg("--version").output() {
132 Ok(output) => output,
133 Err(_) => return None,
134 };
135
136 let version = match str::from_utf8(&output.stdout) {
137 Ok(version) => version,
138 Err(_) => return None,
139 };
140
141 let mut pieces = version.split('.');
142 if pieces.next() != Some("rustc 1") {
143 return None;
144 }
145
146 let next = match pieces.next() {
147 Some(next) => next,
148 None => return None,
149 };
150
151 u32::from_str(next).ok()
152 }
153