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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
//! Configuration used by PyO3 for conditional support of varying Python versions.
//!
//! This crate exposes functionality to be called from build scripts to simplify building crates
//! which depend on PyO3.
//!
//! It used internally by the PyO3 crate's build script to apply the same configuration.

#![warn(elided_lifetimes_in_paths, unused_lifetimes)]

mod errors;
mod impl_;

#[cfg(feature = "resolve-config")]
use std::{
    io::Cursor,
    path::{Path, PathBuf},
};

use std::{env, process::Command};

#[cfg(feature = "resolve-config")]
use once_cell::sync::OnceCell;

#[allow(deprecated)]
pub use impl_::{
    cross_compiling, cross_compiling_from_to, find_all_sysconfigdata, parse_sysconfigdata,
    BuildFlag, BuildFlags, CrossCompileConfig, InterpreterConfig, PythonImplementation,
    PythonVersion, Triple,
};

/// Adds all the [`#[cfg]` flags](index.html) to the current compilation.
///
/// This should be called from a build script.
///
/// The full list of attributes added are the following:
///
/// | Flag | Description |
/// | ---- | ----------- |
/// | `#[cfg(Py_3_7)]`, `#[cfg(Py_3_8)]`, `#[cfg(Py_3_9)]`, `#[cfg(Py_3_10)]` | These attributes mark code only for a given Python version and up. For example, `#[cfg(Py_3_7)]` marks code which can run on Python 3.7 **and newer**. |
/// | `#[cfg(Py_LIMITED_API)]` | This marks code which is run when compiling with PyO3's `abi3` feature enabled. |
/// | `#[cfg(PyPy)]` | This marks code which is run when compiling for PyPy. |
///
/// For examples of how to use these attributes, [see PyO3's guide](https://pyo3.rs/latest/building_and_distribution/multiple_python_versions.html).
#[cfg(feature = "resolve-config")]
pub fn use_pyo3_cfgs() {
    get().emit_pyo3_cfgs();
}

/// Adds linker arguments (for macOS) suitable for PyO3's `extension-module` feature.
///
/// This should be called from a build script.
///
/// This is currently a no-op on non-macOS platforms, however may emit additional linker arguments
/// in future if deemed necessarys.
pub fn add_extension_module_link_args() {
    _add_extension_module_link_args(
        &impl_::cargo_env_var("CARGO_CFG_TARGET_OS").unwrap(),
        std::io::stdout(),
    )
}

fn _add_extension_module_link_args(target_os: &str, mut writer: impl std::io::Write) {
    if target_os == "macos" {
        writeln!(writer, "cargo:rustc-cdylib-link-arg=-undefined").unwrap();
        writeln!(writer, "cargo:rustc-cdylib-link-arg=dynamic_lookup").unwrap();
    }
}

/// Loads the configuration determined from the build environment.
///
/// Because this will never change in a given compilation run, this is cached in a `once_cell`.
#[cfg(feature = "resolve-config")]
pub fn get() -> &'static InterpreterConfig {
    static CONFIG: OnceCell<InterpreterConfig> = OnceCell::new();
    CONFIG.get_or_init(|| {
        // Check if we are in a build script and cross compiling to a different target.
        let cross_compile_config_path = resolve_cross_compile_config_path();
        let cross_compiling = cross_compile_config_path
            .as_ref()
            .map(|path| path.exists())
            .unwrap_or(false);

        if let Some(interpreter_config) = InterpreterConfig::from_cargo_dep_env() {
            interpreter_config
        } else if !CONFIG_FILE.is_empty() {
            InterpreterConfig::from_reader(Cursor::new(CONFIG_FILE))
        } else if cross_compiling {
            InterpreterConfig::from_path(cross_compile_config_path.as_ref().unwrap())
        } else {
            InterpreterConfig::from_reader(Cursor::new(HOST_CONFIG))
        }
        .expect("failed to parse PyO3 config")
    })
}

/// Build configuration provided by `PYO3_CONFIG_FILE`. May be empty if env var not set.
#[doc(hidden)]
#[cfg(feature = "resolve-config")]
const CONFIG_FILE: &str = include_str!(concat!(env!("OUT_DIR"), "/pyo3-build-config-file.txt"));

/// Build configuration discovered by `pyo3-build-config` build script. Not aware of
/// cross-compilation settings.
#[doc(hidden)]
#[cfg(feature = "resolve-config")]
const HOST_CONFIG: &str = include_str!(concat!(env!("OUT_DIR"), "/pyo3-build-config.txt"));

/// Returns the path where PyO3's build.rs writes its cross compile configuration.
///
/// The config file will be named `$OUT_DIR/<triple>/pyo3-build-config.txt`.
///
/// Must be called from a build script, returns `None` if not.
#[doc(hidden)]
#[cfg(feature = "resolve-config")]
fn resolve_cross_compile_config_path() -> Option<PathBuf> {
    env::var_os("TARGET").map(|target| {
        let mut path = PathBuf::from(env!("OUT_DIR"));
        path.push(Path::new(&target));
        path.push("pyo3-build-config.txt");
        path
    })
}

/// Use certain features if we detect the compiler being used supports them.
///
/// Features may be removed or added as MSRV gets bumped or new features become available,
/// so this function is unstable.
#[doc(hidden)]
pub fn print_feature_cfgs() {
    fn rustc_minor_version() -> Option<u32> {
        let rustc = env::var_os("RUSTC")?;
        let output = Command::new(rustc).arg("--version").output().ok()?;
        let version = core::str::from_utf8(&output.stdout).ok()?;
        let mut pieces = version.split('.');
        if pieces.next() != Some("rustc 1") {
            return None;
        }
        pieces.next()?.parse().ok()
    }

    let rustc_minor_version = rustc_minor_version().unwrap_or(0);

    // Enable use of const generics on Rust 1.51 and greater
    if rustc_minor_version >= 51 {
        println!("cargo:rustc-cfg=min_const_generics");
    }

    // Enable use of std::ptr::addr_of! on Rust 1.51 and greater
    if rustc_minor_version >= 51 {
        println!("cargo:rustc-cfg=addr_of");
    }
}

/// Private exports used in PyO3's build.rs
///
/// Please don't use these - they could change at any time.
#[doc(hidden)]
pub mod pyo3_build_script_impl {
    #[cfg(feature = "resolve-config")]
    use crate::errors::{Context, Result};

    #[cfg(feature = "resolve-config")]
    use super::*;

    pub mod errors {
        pub use crate::errors::*;
    }
    pub use crate::impl_::{
        cargo_env_var, env_var, is_linking_libpython, make_cross_compile_config, InterpreterConfig,
        PythonVersion,
    };

    /// Gets the configuration for use from PyO3's build script.
    ///
    /// Differs from .get() above only in the cross-compile case, where PyO3's build script is
    /// required to generate a new config (as it's the first build script which has access to the
    /// correct value for CARGO_CFG_TARGET_OS).
    #[cfg(feature = "resolve-config")]
    pub fn resolve_interpreter_config() -> Result<InterpreterConfig> {
        if !CONFIG_FILE.is_empty() {
            let mut interperter_config = InterpreterConfig::from_reader(Cursor::new(CONFIG_FILE))?;
            interperter_config.fixup_import_libs()?;
            Ok(interperter_config)
        } else if let Some(interpreter_config) = make_cross_compile_config()? {
            // This is a cross compile and need to write the config file.
            let path = resolve_cross_compile_config_path()
                .expect("resolve_interpreter_config() must be called from a build script");
            let parent_dir = path.parent().ok_or_else(|| {
                format!(
                    "failed to resolve parent directory of config file {}",
                    path.display()
                )
            })?;
            std::fs::create_dir_all(&parent_dir).with_context(|| {
                format!(
                    "failed to create config file directory {}",
                    parent_dir.display()
                )
            })?;
            interpreter_config.to_writer(&mut std::fs::File::create(&path).with_context(
                || format!("failed to create config file at {}", path.display()),
            )?)?;
            Ok(interpreter_config)
        } else {
            InterpreterConfig::from_reader(Cursor::new(HOST_CONFIG))
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn extension_module_link_args() {
        let mut buf = Vec::new();

        // Does nothing on non-mac
        _add_extension_module_link_args("windows", &mut buf);
        assert_eq!(buf, Vec::new());

        _add_extension_module_link_args("macos", &mut buf);
        assert_eq!(
            std::str::from_utf8(&buf).unwrap(),
            "cargo:rustc-cdylib-link-arg=-undefined\n\
             cargo:rustc-cdylib-link-arg=dynamic_lookup\n"
        );
    }
}