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//! How to execute a build script and parse its output.
//!
//! ## Preparing a build script run
//!
//! A [build script] is an optional Rust script Cargo will run before building
//! your package. As of this writing, two kinds of special [`Unit`]s will be
//! constructed when there is a build script in a package.
//!
//! * Build script compilation --- This unit is generally the same as units
//! that would compile other Cargo targets. It will recursively creates units
//! of its dependencies. One biggest difference is that the [`Unit`] of
//! compiling a build script is flagged as [`TargetKind::CustomBuild`].
//! * Build script executaion --- During the construction of the [`UnitGraph`],
//! Cargo inserts a [`Unit`] with [`CompileMode::RunCustomBuild`]. This unit
//! depends on the unit of compiling the associated build script, to ensure
//! the executable is available before running. The [`Work`] of running the
//! build script is prepared in the function [`prepare`].
//!
//! ## Running a build script
//!
//! When running a build script, Cargo is aware of the progress and the result
//! of a build script. Standard output is the chosen interprocess communication
//! between Cargo and build script processes. A set of strings is defined for
//! that purpose. These strings, a.k.a. instructions, are interpreted by
//! [`BuildOutput::parse`] and stored in [`Context::build_script_outputs`].
//! The entire execution work is constructed by [`build_work`].
//!
//! [build script]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html
//! [`TargetKind::CustomBuild`]: crate::core::manifest::TargetKind::CustomBuild
//! [`UnitGraph`]: super::unit_graph::UnitGraph
//! [`CompileMode::RunCustomBuild`]: super::CompileMode
//! [instructions]: https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script
use super::{fingerprint, Context, Job, Unit, Work};
use crate::core::compiler::artifact;
use crate::core::compiler::context::Metadata;
use crate::core::compiler::job_queue::JobState;
use crate::core::{profiles::ProfileRoot, PackageId, Target};
use crate::util::errors::CargoResult;
use crate::util::machine_message::{self, Message};
use crate::util::{internal, profile};
use anyhow::{bail, Context as _};
use cargo_platform::Cfg;
use cargo_util::paths;
use std::collections::hash_map::{Entry, HashMap};
use std::collections::{BTreeSet, HashSet};
use std::path::{Path, PathBuf};
use std::str;
use std::sync::{Arc, Mutex};
/// A build script instruction that tells Cargo to display a warning after the
/// build script has finished running. Read [the doc] for more.
///
/// [the doc]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargo-warning
const CARGO_WARNING: &str = "cargo:warning=";
/// Contains the parsed output of a custom build script.
#[derive(Clone, Debug, Hash, Default)]
pub struct BuildOutput {
/// Paths to pass to rustc with the `-L` flag.
pub library_paths: Vec<PathBuf>,
/// Names and link kinds of libraries, suitable for the `-l` flag.
pub library_links: Vec<String>,
/// Linker arguments suitable to be passed to `-C link-arg=<args>`
pub linker_args: Vec<(LinkArgTarget, String)>,
/// Various `--cfg` flags to pass to the compiler.
pub cfgs: Vec<String>,
/// Various `--check-cfg` flags to pass to the compiler.
pub check_cfgs: Vec<String>,
/// Additional environment variables to run the compiler with.
pub env: Vec<(String, String)>,
/// Metadata to pass to the immediate dependencies.
pub metadata: Vec<(String, String)>,
/// Paths to trigger a rerun of this build script.
/// May be absolute or relative paths (relative to package root).
pub rerun_if_changed: Vec<PathBuf>,
/// Environment variables which, when changed, will cause a rebuild.
pub rerun_if_env_changed: Vec<String>,
/// Warnings generated by this build.
///
/// These are only displayed if this is a "local" package, `-vv` is used,
/// or there is a build error for any target in this package.
pub warnings: Vec<String>,
}
/// Map of packages to build script output.
///
/// This initially starts out as empty. Overridden build scripts get
/// inserted during `build_map`. The rest of the entries are added
/// immediately after each build script runs.
///
/// The `Metadata` is the unique metadata hash for the RunCustomBuild Unit of
/// the package. It needs a unique key, since the build script can be run
/// multiple times with different profiles or features. We can't embed a
/// `Unit` because this structure needs to be shareable between threads.
#[derive(Default)]
pub struct BuildScriptOutputs {
outputs: HashMap<Metadata, BuildOutput>,
}
/// Linking information for a `Unit`.
///
/// See [`build_map`] for more details.
#[derive(Default)]
pub struct BuildScripts {
/// List of build script outputs this Unit needs to include for linking. Each
/// element is an index into `BuildScriptOutputs`.
///
/// Cargo will use this `to_link` vector to add `-L` flags to compiles as we
/// propagate them upwards towards the final build. Note, however, that we
/// need to preserve the ordering of `to_link` to be topologically sorted.
/// This will ensure that build scripts which print their paths properly will
/// correctly pick up the files they generated (if there are duplicates
/// elsewhere).
///
/// To preserve this ordering, the (id, metadata) is stored in two places, once
/// in the `Vec` and once in `seen_to_link` for a fast lookup. We maintain
/// this as we're building interactively below to ensure that the memory
/// usage here doesn't blow up too much.
///
/// For more information, see #2354.
pub to_link: Vec<(PackageId, Metadata)>,
/// This is only used while constructing `to_link` to avoid duplicates.
seen_to_link: HashSet<(PackageId, Metadata)>,
/// Host-only dependencies that have build scripts. Each element is an
/// index into `BuildScriptOutputs`.
///
/// This is the set of transitive dependencies that are host-only
/// (proc-macro, plugin, build-dependency) that contain a build script.
/// Any `BuildOutput::library_paths` path relative to `target` will be
/// added to LD_LIBRARY_PATH so that the compiler can find any dynamic
/// libraries a build script may have generated.
pub plugins: BTreeSet<(PackageId, Metadata)>,
}
/// Dependency information as declared by a build script that might trigger
/// a recompile of itself.
#[derive(Debug)]
pub struct BuildDeps {
/// Absolute path to the file in the target directory that stores the
/// output of the build script.
pub build_script_output: PathBuf,
/// Files that trigger a rebuild if they change.
pub rerun_if_changed: Vec<PathBuf>,
/// Environment variables that trigger a rebuild if they change.
pub rerun_if_env_changed: Vec<String>,
}
/// Represents one of the instructions from `cargo:rustc-link-arg-*` build
/// script instruction family.
///
/// In other words, indicates targets that custom linker arguments applies to.
///
/// See the [build script documentation][1] for more.
///
/// [1]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargorustc-link-argflag
#[derive(Clone, Hash, Debug, PartialEq, Eq)]
pub enum LinkArgTarget {
/// Represents `cargo:rustc-link-arg=FLAG`.
All,
/// Represents `cargo:rustc-cdylib-link-arg=FLAG`.
Cdylib,
/// Represents `cargo:rustc-link-arg-bins=FLAG`.
Bin,
/// Represents `cargo:rustc-link-arg-bin=BIN=FLAG`.
SingleBin(String),
/// Represents `cargo:rustc-link-arg-tests=FLAG`.
Test,
/// Represents `cargo:rustc-link-arg-benches=FLAG`.
Bench,
/// Represents `cargo:rustc-link-arg-examples=FLAG`.
Example,
}
impl LinkArgTarget {
/// Checks if this link type applies to a given [`Target`].
pub fn applies_to(&self, target: &Target) -> bool {
match self {
LinkArgTarget::All => true,
LinkArgTarget::Cdylib => target.is_cdylib(),
LinkArgTarget::Bin => target.is_bin(),
LinkArgTarget::SingleBin(name) => target.is_bin() && target.name() == name,
LinkArgTarget::Test => target.is_test(),
LinkArgTarget::Bench => target.is_bench(),
LinkArgTarget::Example => target.is_exe_example(),
}
}
}
/// Prepares a `Work` that executes the target as a custom build script.
pub fn prepare(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
let _p = profile::start(format!(
"build script prepare: {}/{}",
unit.pkg,
unit.target.name()
));
let metadata = cx.get_run_build_script_metadata(unit);
if cx
.build_script_outputs
.lock()
.unwrap()
.contains_key(metadata)
{
// The output is already set, thus the build script is overridden.
fingerprint::prepare_target(cx, unit, false)
} else {
build_work(cx, unit)
}
}
/// Emits the output of a build script as a [`machine_message::BuildScript`]
/// JSON string to standard output.
fn emit_build_output(
state: &JobState<'_, '_>,
output: &BuildOutput,
out_dir: &Path,
package_id: PackageId,
) -> CargoResult<()> {
let library_paths = output
.library_paths
.iter()
.map(|l| l.display().to_string())
.collect::<Vec<_>>();
let msg = machine_message::BuildScript {
package_id,
linked_libs: &output.library_links,
linked_paths: &library_paths,
cfgs: &output.cfgs,
env: &output.env,
out_dir,
}
.to_json_string();
state.stdout(msg)?;
Ok(())
}
/// Constructs the unit of work of running a build script.
///
/// The construction includes:
///
/// * Set environment variables for the build script run.
/// * Create the output dir (`OUT_DIR`) for the build script output.
/// * Determine if the build script needs a re-run.
/// * Run the build script and store its output.
fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
assert!(unit.mode.is_run_custom_build());
let bcx = &cx.bcx;
let dependencies = cx.unit_deps(unit);
let build_script_unit = dependencies
.iter()
.find(|d| !d.unit.mode.is_run_custom_build() && d.unit.target.is_custom_build())
.map(|d| &d.unit)
.expect("running a script not depending on an actual script");
let script_dir = cx.files().build_script_dir(build_script_unit);
let script_out_dir = cx.files().build_script_out_dir(unit);
let script_run_dir = cx.files().build_script_run_dir(unit);
let build_plan = bcx.build_config.build_plan;
let invocation_name = unit.buildkey();
if let Some(deps) = unit.pkg.manifest().metabuild() {
prepare_metabuild(cx, build_script_unit, deps)?;
}
// Building the command to execute
let to_exec = script_dir.join(unit.target.name());
// Start preparing the process to execute, starting out with some
// environment variables. Note that the profile-related environment
// variables are not set with this the build script's profile but rather the
// package's library profile.
// NOTE: if you add any profile flags, be sure to update
// `Profiles::get_profile_run_custom_build` so that those flags get
// carried over.
let to_exec = to_exec.into_os_string();
let mut cmd = cx.compilation.host_process(to_exec, &unit.pkg)?;
let debug = unit.profile.debuginfo.is_turned_on();
cmd.env("OUT_DIR", &script_out_dir)
.env("CARGO_MANIFEST_DIR", unit.pkg.root())
.env("NUM_JOBS", &bcx.jobs().to_string())
.env("TARGET", bcx.target_data.short_name(&unit.kind))
.env("DEBUG", debug.to_string())
.env("OPT_LEVEL", &unit.profile.opt_level)
.env(
"PROFILE",
match unit.profile.root {
ProfileRoot::Release => "release",
ProfileRoot::Debug => "debug",
},
)
.env("HOST", &bcx.host_triple())
.env("RUSTC", &bcx.rustc().path)
.env("RUSTDOC", &*bcx.config.rustdoc()?)
.inherit_jobserver(&cx.jobserver);
// Find all artifact dependencies and make their file and containing directory discoverable using environment variables.
for (var, value) in artifact::get_env(cx, dependencies)? {
cmd.env(&var, value);
}
if let Some(linker) = &cx.compilation.target_linker(unit.kind) {
cmd.env("RUSTC_LINKER", linker);
}
if let Some(links) = unit.pkg.manifest().links() {
cmd.env("CARGO_MANIFEST_LINKS", links);
}
// Be sure to pass along all enabled features for this package, this is the
// last piece of statically known information that we have.
for feat in &unit.features {
cmd.env(&format!("CARGO_FEATURE_{}", super::envify(feat)), "1");
}
let mut cfg_map = HashMap::new();
for cfg in bcx.target_data.cfg(unit.kind) {
match *cfg {
Cfg::Name(ref n) => {
cfg_map.insert(n.clone(), Vec::new());
}
Cfg::KeyPair(ref k, ref v) => {
let values = cfg_map.entry(k.clone()).or_default();
values.push(v.clone());
}
}
}
for (k, v) in cfg_map {
if k == "debug_assertions" {
// This cfg is always true and misleading, so avoid setting it.
// That is because Cargo queries rustc without any profile settings.
continue;
}
let k = format!("CARGO_CFG_{}", super::envify(&k));
cmd.env(&k, v.join(","));
}
// Also inform the build script of the rustc compiler context.
if let Some(wrapper) = bcx.rustc().wrapper.as_ref() {
cmd.env("RUSTC_WRAPPER", wrapper);
} else {
cmd.env_remove("RUSTC_WRAPPER");
}
cmd.env_remove("RUSTC_WORKSPACE_WRAPPER");
if cx.bcx.ws.is_member(&unit.pkg) {
if let Some(wrapper) = bcx.rustc().workspace_wrapper.as_ref() {
cmd.env("RUSTC_WORKSPACE_WRAPPER", wrapper);
}
}
cmd.env(
"CARGO_ENCODED_RUSTFLAGS",
bcx.rustflags_args(unit).join("\x1f"),
);
cmd.env_remove("RUSTFLAGS");
// Gather the set of native dependencies that this package has along with
// some other variables to close over.
//
// This information will be used at build-time later on to figure out which
// sorts of variables need to be discovered at that time.
let lib_deps = dependencies
.iter()
.filter_map(|dep| {
if dep.unit.mode.is_run_custom_build() {
let dep_metadata = cx.get_run_build_script_metadata(&dep.unit);
Some((
dep.unit.pkg.manifest().links().unwrap().to_string(),
dep.unit.pkg.package_id(),
dep_metadata,
))
} else {
None
}
})
.collect::<Vec<_>>();
let library_name = unit.pkg.library().map(|t| t.crate_name());
let pkg_descr = unit.pkg.to_string();
let build_script_outputs = Arc::clone(&cx.build_script_outputs);
let id = unit.pkg.package_id();
let output_file = script_run_dir.join("output");
let err_file = script_run_dir.join("stderr");
let root_output_file = script_run_dir.join("root-output");
let host_target_root = cx.files().host_dest().to_path_buf();
let all = (
id,
library_name.clone(),
pkg_descr.clone(),
Arc::clone(&build_script_outputs),
output_file.clone(),
script_out_dir.clone(),
);
let build_scripts = cx.build_scripts.get(unit).cloned();
let json_messages = bcx.build_config.emit_json();
let extra_verbose = bcx.config.extra_verbose();
let (prev_output, prev_script_out_dir) = prev_build_output(cx, unit);
let metadata_hash = cx.get_run_build_script_metadata(unit);
paths::create_dir_all(&script_dir)?;
paths::create_dir_all(&script_out_dir)?;
let nightly_features_allowed = cx.bcx.config.nightly_features_allowed;
let extra_check_cfg = match cx.bcx.config.cli_unstable().check_cfg {
Some((_, _, _, output)) => output,
None => false,
};
let targets: Vec<Target> = unit.pkg.targets().to_vec();
// Need a separate copy for the fresh closure.
let targets_fresh = targets.clone();
let env_profile_name = unit.profile.name.to_uppercase();
let built_with_debuginfo = cx
.bcx
.unit_graph
.get(unit)
.and_then(|deps| deps.iter().find(|dep| dep.unit.target == unit.target))
.map(|dep| dep.unit.profile.debuginfo.is_turned_on())
.unwrap_or(false);
// Prepare the unit of "dirty work" which will actually run the custom build
// command.
//
// Note that this has to do some extra work just before running the command
// to determine extra environment variables and such.
let dirty = Work::new(move |state| {
// Make sure that OUT_DIR exists.
//
// If we have an old build directory, then just move it into place,
// otherwise create it!
paths::create_dir_all(&script_out_dir)
.with_context(|| "failed to create script output directory for build command")?;
// For all our native lib dependencies, pick up their metadata to pass
// along to this custom build command. We're also careful to augment our
// dynamic library search path in case the build script depended on any
// native dynamic libraries.
if !build_plan {
let build_script_outputs = build_script_outputs.lock().unwrap();
for (name, dep_id, dep_metadata) in lib_deps {
let script_output = build_script_outputs.get(dep_metadata).ok_or_else(|| {
internal(format!(
"failed to locate build state for env vars: {}/{}",
dep_id, dep_metadata
))
})?;
let data = &script_output.metadata;
for (key, value) in data.iter() {
cmd.env(
&format!("DEP_{}_{}", super::envify(&name), super::envify(key)),
value,
);
}
}
if let Some(build_scripts) = build_scripts {
super::add_plugin_deps(
&mut cmd,
&build_script_outputs,
&build_scripts,
&host_target_root,
)?;
}
}
if build_plan {
state.build_plan(invocation_name, cmd.clone(), Arc::new(Vec::new()));
return Ok(());
}
// And now finally, run the build command itself!
state.running(&cmd);
let timestamp = paths::set_invocation_time(&script_run_dir)?;
let prefix = format!("[{} {}] ", id.name(), id.version());
let mut warnings_in_case_of_panic = Vec::new();
let output = cmd
.exec_with_streaming(
&mut |stdout| {
if let Some(warning) = stdout.strip_prefix(CARGO_WARNING) {
warnings_in_case_of_panic.push(warning.to_owned());
}
if extra_verbose {
state.stdout(format!("{}{}", prefix, stdout))?;
}
Ok(())
},
&mut |stderr| {
if extra_verbose {
state.stderr(format!("{}{}", prefix, stderr))?;
}
Ok(())
},
true,
)
.with_context(|| {
let mut build_error_context =
format!("failed to run custom build command for `{}`", pkg_descr);
// If we're opting into backtraces, mention that build dependencies' backtraces can
// be improved by requesting debuginfo to be built, if we're not building with
// debuginfo already.
//
// ALLOWED: Other tools like `rustc` might read it directly
// through `std::env`. We should make their behavior consistent.
#[allow(clippy::disallowed_methods)]
if let Ok(show_backtraces) = std::env::var("RUST_BACKTRACE") {
if !built_with_debuginfo && show_backtraces != "0" {
build_error_context.push_str(&format!(
"\n\
note: To improve backtraces for build dependencies, set the \
CARGO_PROFILE_{env_profile_name}_BUILD_OVERRIDE_DEBUG=true environment \
variable to enable debug information generation.",
));
}
}
build_error_context
});
if let Err(error) = output {
insert_warnings_in_build_outputs(
build_script_outputs,
id,
metadata_hash,
warnings_in_case_of_panic,
);
return Err(error);
}
let output = output.unwrap();
// After the build command has finished running, we need to be sure to
// remember all of its output so we can later discover precisely what it
// was, even if we don't run the build command again (due to freshness).
//
// This is also the location where we provide feedback into the build
// state informing what variables were discovered via our script as
// well.
paths::write(&output_file, &output.stdout)?;
// This mtime shift allows Cargo to detect if a source file was
// modified in the middle of the build.
paths::set_file_time_no_err(output_file, timestamp);
paths::write(&err_file, &output.stderr)?;
paths::write(&root_output_file, paths::path2bytes(&script_out_dir)?)?;
let parsed_output = BuildOutput::parse(
&output.stdout,
library_name,
&pkg_descr,
&script_out_dir,
&script_out_dir,
extra_check_cfg,
nightly_features_allowed,
&targets,
)?;
if json_messages {
emit_build_output(state, &parsed_output, script_out_dir.as_path(), id)?;
}
build_script_outputs
.lock()
.unwrap()
.insert(id, metadata_hash, parsed_output);
Ok(())
});
// Now that we've prepared our work-to-do, we need to prepare the fresh work
// itself to run when we actually end up just discarding what we calculated
// above.
let fresh = Work::new(move |state| {
let (id, library_name, pkg_descr, build_script_outputs, output_file, script_out_dir) = all;
let output = match prev_output {
Some(output) => output,
None => BuildOutput::parse_file(
&output_file,
library_name,
&pkg_descr,
&prev_script_out_dir,
&script_out_dir,
extra_check_cfg,
nightly_features_allowed,
&targets_fresh,
)?,
};
if json_messages {
emit_build_output(state, &output, script_out_dir.as_path(), id)?;
}
build_script_outputs
.lock()
.unwrap()
.insert(id, metadata_hash, output);
Ok(())
});
let mut job = if cx.bcx.build_config.build_plan {
Job::new_dirty(Work::noop(), None)
} else {
fingerprint::prepare_target(cx, unit, false)?
};
if job.freshness().is_dirty() {
job.before(dirty);
} else {
job.before(fresh);
}
Ok(job)
}
/// When a build script run fails, store only warnings and nuke other outputs,
/// as they are likely broken.
fn insert_warnings_in_build_outputs(
build_script_outputs: Arc<Mutex<BuildScriptOutputs>>,
id: PackageId,
metadata_hash: Metadata,
warnings: Vec<String>,
) {
let build_output_with_only_warnings = BuildOutput {
warnings,
..BuildOutput::default()
};
build_script_outputs
.lock()
.unwrap()
.insert(id, metadata_hash, build_output_with_only_warnings);
}
impl BuildOutput {
/// Like [`BuildOutput::parse`] but from a file path.
pub fn parse_file(
path: &Path,
library_name: Option<String>,
pkg_descr: &str,
script_out_dir_when_generated: &Path,
script_out_dir: &Path,
extra_check_cfg: bool,
nightly_features_allowed: bool,
targets: &[Target],
) -> CargoResult<BuildOutput> {
let contents = paths::read_bytes(path)?;
BuildOutput::parse(
&contents,
library_name,
pkg_descr,
script_out_dir_when_generated,
script_out_dir,
extra_check_cfg,
nightly_features_allowed,
targets,
)
}
/// Parses the output instructions of a build script.
///
/// * `pkg_descr` --- for error messages
/// * `library_name` --- for determining if `RUSTC_BOOTSTRAP` should be allowed
/// * `extra_check_cfg` --- for unstable feature [`-Zcheck-cfg`]
///
/// [`-Zcheck-cfg`]: https://doc.rust-lang.org/cargo/reference/unstable.html#check-cfg
pub fn parse(
input: &[u8],
// Takes String instead of InternedString so passing `unit.pkg.name()` will give a compile error.
library_name: Option<String>,
pkg_descr: &str,
script_out_dir_when_generated: &Path,
script_out_dir: &Path,
extra_check_cfg: bool,
nightly_features_allowed: bool,
targets: &[Target],
) -> CargoResult<BuildOutput> {
let mut library_paths = Vec::new();
let mut library_links = Vec::new();
let mut linker_args = Vec::new();
let mut cfgs = Vec::new();
let mut check_cfgs = Vec::new();
let mut env = Vec::new();
let mut metadata = Vec::new();
let mut rerun_if_changed = Vec::new();
let mut rerun_if_env_changed = Vec::new();
let mut warnings = Vec::new();
let whence = format!("build script of `{}`", pkg_descr);
for line in input.split(|b| *b == b'\n') {
let line = match str::from_utf8(line) {
Ok(line) => line.trim(),
Err(..) => continue,
};
let data = match line.split_once(':') {
Some(("cargo", val)) => {
if val.starts_with(":") {
// Line started with `cargo::`.
bail!("unsupported output in {whence}: `{line}`\n\
Found a `cargo::key=value` build directive which is reserved for future use.\n\
Either change the directive to `cargo:key=value` syntax (note the single `:`) or upgrade your version of Rust.\n\
See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
for more information about build script outputs.");
}
val
}
_ => continue,
};
// getting the `key=value` part of the line
let (key, value) = match data.split_once('=') {
Some((a,b)) => (a, b.trim_end()),
// Line started with `cargo:` but didn't match `key=value`.
_ => bail!("invalid output in {}: `{}`\n\
Expected a line with `cargo:key=value` with an `=` character, \
but none was found.\n\
See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
for more information about build script outputs.", whence, line),
};
// This will rewrite paths if the target directory has been moved.
let value = value.replace(
script_out_dir_when_generated.to_str().unwrap(),
script_out_dir.to_str().unwrap(),
);
macro_rules! check_and_add_target {
($target_kind: expr, $is_target_kind: expr, $link_type: expr) => {
if !targets.iter().any(|target| $is_target_kind(target)) {
bail!(
"invalid instruction `cargo:{}` from {}\n\
The package {} does not have a {} target.",
key,
whence,
pkg_descr,
$target_kind
);
}
linker_args.push(($link_type, value));
};
}
// Keep in sync with TargetConfig::parse_links_overrides.
match key {
"rustc-flags" => {
let (paths, links) = BuildOutput::parse_rustc_flags(&value, &whence)?;
library_links.extend(links.into_iter());
library_paths.extend(paths.into_iter());
}
"rustc-link-lib" => library_links.push(value.to_string()),
"rustc-link-search" => library_paths.push(PathBuf::from(value)),
"rustc-link-arg-cdylib" | "rustc-cdylib-link-arg" => {
if !targets.iter().any(|target| target.is_cdylib()) {
warnings.push(format!(
"cargo:{} was specified in the build script of {}, \
but that package does not contain a cdylib target\n\
\n\
Allowing this was an unintended change in the 1.50 \
release, and may become an error in the future. \
For more information, see \
<https://github.com/rust-lang/cargo/issues/9562>.",
key, pkg_descr
));
}
linker_args.push((LinkArgTarget::Cdylib, value))
}
"rustc-link-arg-bins" => {
check_and_add_target!("bin", Target::is_bin, LinkArgTarget::Bin);
}
"rustc-link-arg-bin" => {
let (bin_name, arg) = value.split_once('=').ok_or_else(|| {
anyhow::format_err!(
"invalid instruction `cargo:{}={}` from {}\n\
The instruction should have the form cargo:{}=BIN=ARG",
key,
value,
whence,
key
)
})?;
if !targets
.iter()
.any(|target| target.is_bin() && target.name() == bin_name)
{
bail!(
"invalid instruction `cargo:{}` from {}\n\
The package {} does not have a bin target with the name `{}`.",
key,
whence,
pkg_descr,
bin_name
);
}
linker_args.push((
LinkArgTarget::SingleBin(bin_name.to_owned()),
arg.to_string(),
));
}
"rustc-link-arg-tests" => {
check_and_add_target!("test", Target::is_test, LinkArgTarget::Test);
}
"rustc-link-arg-benches" => {
check_and_add_target!("benchmark", Target::is_bench, LinkArgTarget::Bench);
}
"rustc-link-arg-examples" => {
check_and_add_target!("example", Target::is_example, LinkArgTarget::Example);
}
"rustc-link-arg" => {
linker_args.push((LinkArgTarget::All, value));
}
"rustc-cfg" => cfgs.push(value.to_string()),
"rustc-check-cfg" => {
if extra_check_cfg {
check_cfgs.push(value.to_string());
} else {
warnings.push(format!("cargo:{} requires -Zcheck-cfg=output flag", key));
}
}
"rustc-env" => {
let (key, val) = BuildOutput::parse_rustc_env(&value, &whence)?;
// Build scripts aren't allowed to set RUSTC_BOOTSTRAP.
// See https://github.com/rust-lang/cargo/issues/7088.
if key == "RUSTC_BOOTSTRAP" {
// If RUSTC_BOOTSTRAP is already set, the user of Cargo knows about
// bootstrap and still wants to override the channel. Give them a way to do
// so, but still emit a warning that the current crate shouldn't be trying
// to set RUSTC_BOOTSTRAP.
// If this is a nightly build, setting RUSTC_BOOTSTRAP wouldn't affect the
// behavior, so still only give a warning.
// NOTE: cargo only allows nightly features on RUSTC_BOOTSTRAP=1, but we
// want setting any value of RUSTC_BOOTSTRAP to downgrade this to a warning
// (so that `RUSTC_BOOTSTRAP=library_name` will work)
let rustc_bootstrap_allows = |name: Option<&str>| {
let name = match name {
// as of 2021, no binaries on crates.io use RUSTC_BOOTSTRAP, so
// fine-grained opt-outs aren't needed. end-users can always use
// RUSTC_BOOTSTRAP=1 from the top-level if it's really a problem.
None => return false,
Some(n) => n,
};
// ALLOWED: the process of rustc bootstrapping reads this through
// `std::env`. We should make the behavior consistent. Also, we
// don't advertise this for bypassing nightly.
#[allow(clippy::disallowed_methods)]
std::env::var("RUSTC_BOOTSTRAP")
.map_or(false, |var| var.split(',').any(|s| s == name))
};
if nightly_features_allowed
|| rustc_bootstrap_allows(library_name.as_deref())
{
warnings.push(format!("Cannot set `RUSTC_BOOTSTRAP={}` from {}.\n\
note: Crates cannot set `RUSTC_BOOTSTRAP` themselves, as doing so would subvert the stability guarantees of Rust for your project.",
val, whence
));
} else {
// Setting RUSTC_BOOTSTRAP would change the behavior of the crate.
// Abort with an error.
bail!("Cannot set `RUSTC_BOOTSTRAP={}` from {}.\n\
note: Crates cannot set `RUSTC_BOOTSTRAP` themselves, as doing so would subvert the stability guarantees of Rust for your project.\n\
help: If you're sure you want to do this in your project, set the environment variable `RUSTC_BOOTSTRAP={}` before running cargo instead.",
val,
whence,
library_name.as_deref().unwrap_or("1"),
);
}
} else {
env.push((key, val));
}
}
"warning" => warnings.push(value.to_string()),
"rerun-if-changed" => rerun_if_changed.push(PathBuf::from(value)),
"rerun-if-env-changed" => rerun_if_env_changed.push(value.to_string()),
_ => metadata.push((key.to_string(), value.to_string())),
}
}
Ok(BuildOutput {
library_paths,
library_links,
linker_args,
cfgs,
check_cfgs,
env,
metadata,
rerun_if_changed,
rerun_if_env_changed,
warnings,
})
}
/// Parses [`cargo:rustc-flags`] instruction.
///
/// [`cargo:rustc-flags`]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#cargorustc-flagsflags
pub fn parse_rustc_flags(
value: &str,
whence: &str,
) -> CargoResult<(Vec<PathBuf>, Vec<String>)> {
let value = value.trim();
let mut flags_iter = value
.split(|c: char| c.is_whitespace())
.filter(|w| w.chars().any(|c| !c.is_whitespace()));
let (mut library_paths, mut library_links) = (Vec::new(), Vec::new());
while let Some(flag) = flags_iter.next() {
if flag.starts_with("-l") || flag.starts_with("-L") {
// Check if this flag has no space before the value as is
// common with tools like pkg-config
// e.g. -L/some/dir/local/lib or -licui18n
let (flag, mut value) = flag.split_at(2);
if value.is_empty() {
value = match flags_iter.next() {
Some(v) => v,
None => bail! {
"Flag in rustc-flags has no value in {}: {}",
whence,
value
},
}
}
match flag {
"-l" => library_links.push(value.to_string()),
"-L" => library_paths.push(PathBuf::from(value)),
// This was already checked above
_ => unreachable!(),
};
} else {
bail!(
"Only `-l` and `-L` flags are allowed in {}: `{}`",
whence,
value
)
}
}
Ok((library_paths, library_links))
}
/// Parses [`cargo:rustc-env`] instruction.
///
/// [`cargo:rustc-env`]: https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-env
pub fn parse_rustc_env(value: &str, whence: &str) -> CargoResult<(String, String)> {
match value.split_once('=') {
Some((n, v)) => Ok((n.to_owned(), v.to_owned())),
_ => bail!("Variable rustc-env has no value in {whence}: {value}"),
}
}
}
/// Prepares the Rust script for the unstable feature [metabuild].
///
/// [metabuild]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#metabuild
fn prepare_metabuild(cx: &Context<'_, '_>, unit: &Unit, deps: &[String]) -> CargoResult<()> {
let mut output = Vec::new();
let available_deps = cx.unit_deps(unit);
// Filter out optional dependencies, and look up the actual lib name.
let meta_deps: Vec<_> = deps
.iter()
.filter_map(|name| {
available_deps
.iter()
.find(|d| d.unit.pkg.name().as_str() == name.as_str())
.map(|d| d.unit.target.crate_name())
})
.collect();
for dep in &meta_deps {
output.push(format!("use {};\n", dep));
}
output.push("fn main() {\n".to_string());
for dep in &meta_deps {
output.push(format!(" {}::metabuild();\n", dep));
}
output.push("}\n".to_string());
let output = output.join("");
let path = unit.pkg.manifest().metabuild_path(cx.bcx.ws.target_dir());
paths::create_dir_all(path.parent().unwrap())?;
paths::write_if_changed(path, &output)?;
Ok(())
}
impl BuildDeps {
/// Creates a build script dependency information from a previous
/// build script output path and the content.
pub fn new(output_file: &Path, output: Option<&BuildOutput>) -> BuildDeps {
BuildDeps {
build_script_output: output_file.to_path_buf(),
rerun_if_changed: output
.map(|p| &p.rerun_if_changed)
.cloned()
.unwrap_or_default(),
rerun_if_env_changed: output
.map(|p| &p.rerun_if_env_changed)
.cloned()
.unwrap_or_default(),
}
}
}
/// Computes several maps in [`Context`].
///
/// - [`build_scripts`]: A map that tracks which build scripts each package
/// depends on.
/// - [`build_explicit_deps`]: Dependency statements emitted by build scripts
/// from a previous run.
/// - [`build_script_outputs`]: Pre-populates this with any overridden build
/// scripts.
///
/// The important one here is [`build_scripts`], which for each `(package,
/// metadata)` stores a [`BuildScripts`] object which contains a list of
/// dependencies with build scripts that the unit should consider when linking.
/// For example this lists all dependencies' `-L` flags which need to be
/// propagated transitively.
///
/// The given set of units to this function is the initial set of
/// targets/profiles which are being built.
///
/// [`build_scripts`]: Context::build_scripts
/// [`build_explicit_deps`]: Context::build_explicit_deps
/// [`build_script_outputs`]: Context::build_script_outputs
pub fn build_map(cx: &mut Context<'_, '_>) -> CargoResult<()> {
let mut ret = HashMap::new();
for unit in &cx.bcx.roots {
build(&mut ret, cx, unit)?;
}
cx.build_scripts
.extend(ret.into_iter().map(|(k, v)| (k, Arc::new(v))));
return Ok(());
// Recursive function to build up the map we're constructing. This function
// memoizes all of its return values as it goes along.
fn build<'a>(
out: &'a mut HashMap<Unit, BuildScripts>,
cx: &mut Context<'_, '_>,
unit: &Unit,
) -> CargoResult<&'a BuildScripts> {
// Do a quick pre-flight check to see if we've already calculated the
// set of dependencies.
if out.contains_key(unit) {
return Ok(&out[unit]);
}
// If there is a build script override, pre-fill the build output.
if unit.mode.is_run_custom_build() {
if let Some(links) = unit.pkg.manifest().links() {
if let Some(output) = cx.bcx.target_data.script_override(links, unit.kind) {
let metadata = cx.get_run_build_script_metadata(unit);
cx.build_script_outputs.lock().unwrap().insert(
unit.pkg.package_id(),
metadata,
output.clone(),
);
}
}
}
let mut ret = BuildScripts::default();
// If a package has a build script, add itself as something to inspect for linking.
if !unit.target.is_custom_build() && unit.pkg.has_custom_build() {
let script_meta = cx
.find_build_script_metadata(unit)
.expect("has_custom_build should have RunCustomBuild");
add_to_link(&mut ret, unit.pkg.package_id(), script_meta);
}
if unit.mode.is_run_custom_build() {
parse_previous_explicit_deps(cx, unit);
}
// We want to invoke the compiler deterministically to be cache-friendly
// to rustc invocation caching schemes, so be sure to generate the same
// set of build script dependency orderings via sorting the targets that
// come out of the `Context`.
let mut dependencies: Vec<Unit> =
cx.unit_deps(unit).iter().map(|d| d.unit.clone()).collect();
dependencies.sort_by_key(|u| u.pkg.package_id());
for dep_unit in dependencies.iter() {
let dep_scripts = build(out, cx, dep_unit)?;
if dep_unit.target.for_host() {
ret.plugins.extend(dep_scripts.to_link.iter().cloned());
} else if dep_unit.target.is_linkable() {
for &(pkg, metadata) in dep_scripts.to_link.iter() {
add_to_link(&mut ret, pkg, metadata);
}
}
}
match out.entry(unit.clone()) {
Entry::Vacant(entry) => Ok(entry.insert(ret)),
Entry::Occupied(_) => panic!("cyclic dependencies in `build_map`"),
}
}
// When adding an entry to 'to_link' we only actually push it on if the
// script hasn't seen it yet (e.g., we don't push on duplicates).
fn add_to_link(scripts: &mut BuildScripts, pkg: PackageId, metadata: Metadata) {
if scripts.seen_to_link.insert((pkg, metadata)) {
scripts.to_link.push((pkg, metadata));
}
}
/// Load any dependency declarations from a previous build script run.
fn parse_previous_explicit_deps(cx: &mut Context<'_, '_>, unit: &Unit) {
let script_run_dir = cx.files().build_script_run_dir(unit);
let output_file = script_run_dir.join("output");
let (prev_output, _) = prev_build_output(cx, unit);
let deps = BuildDeps::new(&output_file, prev_output.as_ref());
cx.build_explicit_deps.insert(unit.clone(), deps);
}
}
/// Returns the previous parsed `BuildOutput`, if any, from a previous
/// execution.
///
/// Also returns the directory containing the output, typically used later in
/// processing.
fn prev_build_output(cx: &mut Context<'_, '_>, unit: &Unit) -> (Option<BuildOutput>, PathBuf) {
let script_out_dir = cx.files().build_script_out_dir(unit);
let script_run_dir = cx.files().build_script_run_dir(unit);
let root_output_file = script_run_dir.join("root-output");
let output_file = script_run_dir.join("output");
let prev_script_out_dir = paths::read_bytes(&root_output_file)
.and_then(|bytes| paths::bytes2path(&bytes))
.unwrap_or_else(|_| script_out_dir.clone());
(
BuildOutput::parse_file(
&output_file,
unit.pkg.library().map(|t| t.crate_name()),
&unit.pkg.to_string(),
&prev_script_out_dir,
&script_out_dir,
match cx.bcx.config.cli_unstable().check_cfg {
Some((_, _, _, output)) => output,
None => false,
},
cx.bcx.config.nightly_features_allowed,
unit.pkg.targets(),
)
.ok(),
prev_script_out_dir,
)
}
impl BuildScriptOutputs {
/// Inserts a new entry into the map.
fn insert(&mut self, pkg_id: PackageId, metadata: Metadata, parsed_output: BuildOutput) {
match self.outputs.entry(metadata) {
Entry::Vacant(entry) => {
entry.insert(parsed_output);
}
Entry::Occupied(entry) => panic!(
"build script output collision for {}/{}\n\
old={:?}\nnew={:?}",
pkg_id,
metadata,
entry.get(),
parsed_output
),
}
}
/// Returns `true` if the given key already exists.
fn contains_key(&self, metadata: Metadata) -> bool {
self.outputs.contains_key(&metadata)
}
/// Gets the build output for the given key.
pub fn get(&self, meta: Metadata) -> Option<&BuildOutput> {
self.outputs.get(&meta)
}
/// Returns an iterator over all entries.
pub fn iter(&self) -> impl Iterator<Item = (&Metadata, &BuildOutput)> {
self.outputs.iter()
}
}