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//! Types and impls for [`Unit`].
use crate::core::compiler::unit_dependencies::IsArtifact;
use crate::core::compiler::{CompileKind, CompileMode, CompileTarget, CrateType};
use crate::core::manifest::{Target, TargetKind};
use crate::core::profiles::Profile;
use crate::core::Package;
use crate::util::hex::short_hash;
use crate::util::interning::InternedString;
use crate::util::Config;
use std::cell::RefCell;
use std::collections::HashSet;
use std::fmt;
use std::hash::{Hash, Hasher};
use std::ops::Deref;
use std::rc::Rc;
/// All information needed to define a unit.
///
/// A unit is an object that has enough information so that cargo knows how to build it.
/// For example, if your package has dependencies, then every dependency will be built as a library
/// unit. If your package is a library, then it will be built as a library unit as well, or if it
/// is a binary with `main.rs`, then a binary will be output. There are also separate unit types
/// for `test`ing and `check`ing, amongst others.
///
/// The unit also holds information about all possible metadata about the package in `pkg`.
///
/// A unit needs to know extra information in addition to the type and root source file. For
/// example, it needs to know the target architecture (OS, chip arch etc.) and it needs to know
/// whether you want a debug or release build. There is enough information in this struct to figure
/// all that out.
#[derive(Clone, PartialOrd, Ord)]
pub struct Unit {
inner: Rc<UnitInner>,
}
/// Internal fields of `Unit` which `Unit` will dereference to.
#[derive(Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct UnitInner {
/// Information about available targets, which files to include/exclude, etc. Basically stuff in
/// `Cargo.toml`.
pub pkg: Package,
/// Information about the specific target to build, out of the possible targets in `pkg`. Not
/// to be confused with *target-triple* (or *target architecture* ...), the target arch for a
/// build.
pub target: Target,
/// The profile contains information about *how* the build should be run, including debug
/// level, etc.
pub profile: Profile,
/// Whether this compilation unit is for the host or target architecture.
///
/// For example, when
/// cross compiling and using a custom build script, the build script needs to be compiled for
/// the host architecture so the host rustc can use it (when compiling to the target
/// architecture).
pub kind: CompileKind,
/// The "mode" this unit is being compiled for. See [`CompileMode`] for more details.
pub mode: CompileMode,
/// The `cfg` features to enable for this unit.
/// This must be sorted.
pub features: Vec<InternedString>,
// if `true`, the dependency is an artifact dependency, requiring special handling when
// calculating output directories, linkage and environment variables provided to builds.
pub artifact: IsArtifact,
/// Whether this is a standard library unit.
pub is_std: bool,
/// A hash of all dependencies of this unit.
///
/// This is used to keep the `Unit` unique in the situation where two
/// otherwise identical units need to link to different dependencies. This
/// can happen, for example, when there are shared dependencies that need
/// to be built with different features between normal and build
/// dependencies. See `rebuild_unit_graph_shared` for more on why this is
/// done.
///
/// This value initially starts as 0, and then is filled in via a
/// second-pass after all the unit dependencies have been computed.
pub dep_hash: u64,
/// This is used for target-dependent feature resolution and is copied from
/// [`FeaturesFor::ArtifactDep`], if the enum matches the variant.
///
/// [`FeaturesFor::ArtifactDep`]: crate::core::resolver::features::FeaturesFor::ArtifactDep
pub artifact_target_for_features: Option<CompileTarget>,
}
impl UnitInner {
/// Returns whether compilation of this unit requires all upstream artifacts
/// to be available.
///
/// This effectively means that this unit is a synchronization point (if the
/// return value is `true`) that all previously pipelined units need to
/// finish in their entirety before this one is started.
pub fn requires_upstream_objects(&self) -> bool {
self.mode.is_any_test() || self.target.kind().requires_upstream_objects()
}
/// Returns whether or not this is a "local" package.
///
/// A "local" package is one that the user can likely edit, or otherwise
/// wants warnings, etc.
pub fn is_local(&self) -> bool {
self.pkg.package_id().source_id().is_path() && !self.is_std
}
/// Returns whether or not warnings should be displayed for this unit.
pub fn show_warnings(&self, config: &Config) -> bool {
self.is_local() || config.extra_verbose()
}
}
impl Unit {
/// Gets the unique key for [`-Zbuild-plan`].
///
/// [`-Zbuild-plan`]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-plan
pub fn buildkey(&self) -> String {
format!("{}-{}", self.pkg.name(), short_hash(self))
}
}
// Just hash the pointer for fast hashing
impl Hash for Unit {
fn hash<H: Hasher>(&self, hasher: &mut H) {
std::ptr::hash(&*self.inner, hasher)
}
}
// Just equate the pointer since these are interned
impl PartialEq for Unit {
fn eq(&self, other: &Unit) -> bool {
std::ptr::eq(&*self.inner, &*other.inner)
}
}
impl Eq for Unit {}
impl Deref for Unit {
type Target = UnitInner;
fn deref(&self) -> &UnitInner {
&*self.inner
}
}
impl fmt::Debug for Unit {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Unit")
.field("pkg", &self.pkg)
.field("target", &self.target)
.field("profile", &self.profile)
.field("kind", &self.kind)
.field("mode", &self.mode)
.field("features", &self.features)
.field("artifact", &self.artifact.is_true())
.field(
"artifact_target_for_features",
&self.artifact_target_for_features,
)
.field("is_std", &self.is_std)
.field("dep_hash", &self.dep_hash)
.finish()
}
}
/// A small structure used to "intern" `Unit` values.
///
/// A `Unit` is just a thin pointer to an internal `UnitInner`. This is done to
/// ensure that `Unit` itself is quite small as well as enabling a very
/// efficient hash/equality implementation for `Unit`. All units are
/// manufactured through an interner which guarantees that each equivalent value
/// is only produced once.
pub struct UnitInterner {
state: RefCell<InternerState>,
}
struct InternerState {
cache: HashSet<Rc<UnitInner>>,
}
impl UnitInterner {
/// Creates a new blank interner
pub fn new() -> UnitInterner {
UnitInterner {
state: RefCell::new(InternerState {
cache: HashSet::new(),
}),
}
}
/// Creates a new `unit` from its components. The returned `Unit`'s fields
/// will all be equivalent to the provided arguments, although they may not
/// be the exact same instance.
pub fn intern(
&self,
pkg: &Package,
target: &Target,
profile: Profile,
kind: CompileKind,
mode: CompileMode,
features: Vec<InternedString>,
is_std: bool,
dep_hash: u64,
artifact: IsArtifact,
artifact_target_for_features: Option<CompileTarget>,
) -> Unit {
let target = match (is_std, target.kind()) {
// This is a horrible hack to support build-std. `libstd` declares
// itself with both rlib and dylib. We don't want the dylib for a
// few reasons:
//
// - dylibs don't have a hash in the filename. If you do something
// (like switch rustc versions), it will stomp on the dylib
// file, invalidating the entire cache (because std is a dep of
// everything).
// - We don't want to publicize the presence of dylib for the
// standard library.
//
// At some point in the future, it would be nice to have a
// first-class way of overriding or specifying crate-types.
(true, TargetKind::Lib(crate_types)) if crate_types.contains(&CrateType::Dylib) => {
let mut new_target = Target::clone(target);
new_target.set_kind(TargetKind::Lib(vec![CrateType::Rlib]));
new_target
}
_ => target.clone(),
};
let inner = self.intern_inner(&UnitInner {
pkg: pkg.clone(),
target,
profile,
kind,
mode,
features,
is_std,
dep_hash,
artifact,
artifact_target_for_features,
});
Unit { inner }
}
fn intern_inner(&self, item: &UnitInner) -> Rc<UnitInner> {
let mut me = self.state.borrow_mut();
if let Some(item) = me.cache.get(item) {
return item.clone();
}
let item = Rc::new(item.clone());
me.cache.insert(item.clone());
item
}
}