1 // Copyright 2021 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 use std::env;
6 use std::io::Write;
7 use std::path::Path;
8 use std::process::Command;
9 use std::str::{self, FromStr};
10
main()11 fn main() {
12 println!("cargo:rustc-cfg=build_script_ran");
13 let minor = match rustc_minor_version() {
14 Some(minor) => minor,
15 None => return,
16 };
17
18 let target = env::var("TARGET").unwrap();
19
20 if minor >= 34 {
21 println!("cargo:rustc-cfg=is_new_rustc");
22 } else {
23 println!("cargo:rustc-cfg=is_old_rustc");
24 }
25
26 if target.contains("android") {
27 println!("cargo:rustc-cfg=is_android");
28 }
29 if target.contains("darwin") {
30 println!("cargo:rustc-cfg=is_mac");
31 }
32
33 let feature_a_enabled = env::var_os("CARGO_FEATURE_MY_FEATURE_A").is_some();
34 if feature_a_enabled {
35 println!("cargo:rustc-cfg=has_feature_a");
36 }
37 let feature_b_enabled = env::var_os("CARGO_FEATURE_MY_FEATURE_B").is_some();
38 if feature_b_enabled {
39 println!("cargo:rustc-cfg=has_feature_b");
40 }
41
42 // Some tests as to whether we're properly emulating various cargo features.
43 assert!(Path::new(&env::var_os("CARGO_MANIFEST_DIR").unwrap()).join("build.rs").exists());
44 assert!(Path::new("build.rs").exists());
45 assert!(Path::new(&env::var_os("OUT_DIR").unwrap()).exists());
46 // Confirm the following env var is set, but do not attempt to validate content
47 // since the whole point is that it will differ on different platforms.
48 env::var_os("CARGO_CFG_TARGET_ARCH").unwrap();
49
50 generate_some_code().unwrap();
51 }
52
generate_some_code() -> std::io::Result<()>53 fn generate_some_code() -> std::io::Result<()> {
54 let output_dir = Path::new(&env::var_os("OUT_DIR").unwrap()).join("generated");
55 let _ = std::fs::create_dir_all(&output_dir);
56 // Test that environment variables from .gn files are passed to build scripts
57 let preferred_number = env::var("ENV_VAR_FOR_BUILD_SCRIPT").unwrap();
58 let mut file = std::fs::File::create(output_dir.join("generated.rs"))?;
59 write!(file, "fn run_some_generated_code() -> u32 {{ {} }}", preferred_number)?;
60 Ok(())
61 }
62
rustc_minor_version() -> Option<u32>63 fn rustc_minor_version() -> Option<u32> {
64 let rustc = match env::var_os("RUSTC") {
65 Some(rustc) => rustc,
66 None => return None,
67 };
68
69 let output = match Command::new(rustc).arg("--version").output() {
70 Ok(output) => output,
71 Err(_) => return None,
72 };
73
74 let version = match str::from_utf8(&output.stdout) {
75 Ok(version) => version,
76 Err(_) => return None,
77 };
78
79 let mut pieces = version.split('.');
80 if pieces.next() != Some("rustc 1") {
81 return None;
82 }
83
84 let next = match pieces.next() {
85 Some(next) => next,
86 None => return None,
87 };
88
89 u32::from_str(next).ok()
90 }
91