RFC3239: Implement cfg(target)

compiler/rustc_error_codes/src/error_codes/E0455.md

@@ -11,7 +11,10 @@ Erroneous code example:
 To solve this error you can use conditional compilation:
 
 ```
-#[cfg_attr(target="macos", link(name = "FooCoreServices", kind = "framework"))]
+#[cfg_attr(
+    target_os="macos",
+    link(name = "FooCoreServices", kind = "framework")
+)]
 extern "C" {}
 ```
 

compiler/rustc_feature/src/active.rs

@@ -317,6 +317,8 @@ declare_features! (
     (incomplete, capture_disjoint_fields, "1.49.0", Some(53488), None),
     /// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
     (active, cfg_sanitize, "1.41.0", Some(39699), None),
+    /// Allows `cfg(target = "...")`.
+    (active, cfg_target, "1.62.0", Some(96901), None),
     /// Allows `cfg(target_abi = "...")`.
     (active, cfg_target_abi, "1.55.0", Some(80970), None),
     /// Allows `cfg(target_has_atomic_load_store = "...")`.

compiler/rustc_feature/src/builtin_attrs.rs

@@ -24,6 +24,7 @@ pub type GatedCfg = (Symbol, Symbol, GateFn);
 /// `cfg(...)`'s that are feature gated.
 const GATED_CFGS: &[GatedCfg] = &[
     // (name in cfg, feature, function to check if the feature is enabled)
+    (sym::target, sym::cfg_target, cfg_fn!(cfg_target)),
     (sym::target_abi, sym::cfg_target_abi, cfg_fn!(cfg_target_abi)),
     (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
     (

compiler/rustc_session/src/config.rs

@@ -894,6 +894,7 @@ pub const fn default_lib_output() -> CrateType {
 
 fn default_configuration(sess: &Session) -> CrateConfig {
     // NOTE: This should be kept in sync with `CrateCheckConfig::fill_well_known` below.
+    let tar = &sess.opts.target_triple.triple();
     let end = &sess.target.endian;
     let arch = &sess.target.arch;
     let wordsz = sess.target.pointer_width.to_string();
@@ -909,8 +910,10 @@ fn default_configuration(sess: &Session) -> CrateConfig {
     });
 
     let mut ret = FxHashSet::default();
-    ret.reserve(7); // the minimum number of insertions
+    ret.reserve(9); // the minimum number of insertions
+
     // Target bindings.
+    ret.insert((sym::target, Some(Symbol::intern(tar))));
     ret.insert((sym::target_os, Some(Symbol::intern(os))));
     for fam in sess.target.families.as_ref() {
         ret.insert((sym::target_family, Some(Symbol::intern(fam))));
@@ -1031,6 +1034,7 @@ impl CrateCheckConfig {
             // rustc
             sym::unix,
             sym::windows,
+            sym::target,
             sym::target_os,
             sym::target_family,
             sym::target_arch,
@@ -1120,9 +1124,11 @@ impl CrateCheckConfig {
             .extend(atomic_values);
 
         // Target specific values
-        for target in
-            TARGETS.iter().map(|target| Target::expect_builtin(&TargetTriple::from_triple(target)))
+        for (name, target) in TARGETS
+            .iter()
+            .map(|target| (target, Target::expect_builtin(&TargetTriple::from_triple(target))))
         {
+            self.values_valid.entry(sym::target).or_default().insert(Symbol::intern(&name));
             self.values_valid
                 .entry(sym::target_os)
                 .or_default()

compiler/rustc_span/src/symbol.rs

@@ -426,6 +426,7 @@ symbols! {
         cfg_macro,
         cfg_panic,
         cfg_sanitize,
+        cfg_target,
         cfg_target_abi,
         cfg_target_feature,
         cfg_target_has_atomic,
@@ -1374,6 +1375,7 @@ symbols! {
         sym,
         sync,
         t32,
+        target,
         target_abi,
         target_arch,
         target_endian,

src/test/ui/cfg/cfg-target.rs

@@ -0,0 +1,10 @@
+// run-pass
+#![feature(cfg_target)]
+
+#[cfg(target = "x86_64-unknown-linux-gnu")]
+pub fn main() {
+}
+
+#[cfg(not(target = "x86_64-unknown-linux-gnu"))]
+pub fn main() {
+}

src/test/ui/check-cfg/well-known-names.rs

@@ -3,13 +3,22 @@
 // check-pass
 // compile-flags: --check-cfg=names() -Z unstable-options
 
+#![feature(cfg_target)]
+
 #[cfg(target_oz = "linux")]
 //~^ WARNING unexpected `cfg` condition name
 fn target_os_misspell() {}
 
 #[cfg(target_os = "linux")]
 fn target_os() {}
 
+#[cfg(targeT = "x86_64-unknown-linux-gnu")]
+//~^ WARNING unexpected `cfg` condition name
+fn target_misspell() {}
+
+#[cfg(target = "x86_64-unknown-linux-gnu")]
+fn target() {}
+
 #[cfg(features = "foo")]
 //~^ WARNING unexpected `cfg` condition name
 fn feature_misspell() {}

src/test/ui/check-cfg/well-known-names.stderr

@@ -1,5 +1,5 @@
 warning: unexpected `cfg` condition name
-  --> $DIR/well-known-names.rs:6:7
+  --> $DIR/well-known-names.rs:8:7
    |
 LL | #[cfg(target_oz = "linux")]
    |       ---------^^^^^^^^^^
@@ -9,18 +9,26 @@ LL | #[cfg(target_oz = "linux")]
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: unexpected `cfg` condition name
-  --> $DIR/well-known-names.rs:13:7
+  --> $DIR/well-known-names.rs:15:7
+   |
+LL | #[cfg(targeT = "x86_64-unknown-linux-gnu")]
+   |       ------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |       |
+   |       help: did you mean: `target`
+
+warning: unexpected `cfg` condition name
+  --> $DIR/well-known-names.rs:22:7
    |
 LL | #[cfg(features = "foo")]
    |       --------^^^^^^^^
    |       |
    |       help: did you mean: `feature`
 
 warning: unexpected `cfg` condition name
-  --> $DIR/well-known-names.rs:20:7
+  --> $DIR/well-known-names.rs:29:7
    |
 LL | #[cfg(uniw)]
    |       ^^^^ help: did you mean: `unix`
 
-warning: 3 warnings emitted
+warning: 4 warnings emitted
 

src/test/ui/feature-gates/feature-gate-cfg-target.rs

@@ -0,0 +1,13 @@
+#[cfg(target = "x")] //~ ERROR `cfg(target)` is experimental
+struct Foo(u64, u64);
+
+#[cfg_attr(target = "x", x)] //~ ERROR `cfg(target)` is experimental
+struct Bar(u64, u64);
+
+#[cfg(not(any(all(target = "x"))))] //~ ERROR `cfg(target)` is experimental
+fn foo() {}
+
+fn main() {
+    cfg!(target = "x");
+    //~^ ERROR `cfg(target)` is experimental and subject to change
+}

src/test/ui/feature-gates/feature-gate-cfg-target.stderr

@@ -0,0 +1,39 @@
+error[E0658]: `cfg(target)` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target.rs:1:7
+   |
+LL | #[cfg(target = "x")]
+   |       ^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target)]` to the crate attributes to enable
+
+error[E0658]: `cfg(target)` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target.rs:4:12
+   |
+LL | #[cfg_attr(target = "x", x)]
+   |            ^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target)]` to the crate attributes to enable
+
+error[E0658]: `cfg(target)` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target.rs:7:19
+   |
+LL | #[cfg(not(any(all(target = "x"))))]
+   |                   ^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target)]` to the crate attributes to enable
+
+error[E0658]: `cfg(target)` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-target.rs:11:10
+   |
+LL |     cfg!(target = "x");
+   |          ^^^^^^^^^^^^
+   |
+   = note: see issue #96901 <https://github.com/rust-lang/rust/issues/96901> for more information
+   = help: add `#![feature(cfg_target)]` to the crate attributes to enable
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0658`.