[beta] Revert destabilise target-spec-json

This reverts https://github.com/rust-lang/rust/pull/150151 in order to
deal with https://github.com/rust-lang/rust/issues/151729 where the
destabilization caused a problem with building rustc itself with JSON
target specs. There's a fix at
https://github.com/rust-lang/rust/pull/152677, but we would prefer to
not backport that, and instead give ourselves more time to work out the
kinks. Also, the destabilization was incomplete, and the rest of the
changes are in 1.95 (https://github.com/rust-lang/rust/pull/151534 and
https://github.com/rust-lang/cargo/pull/16557), so it would be nice to
keep all the changes together in one release.

This reverts commit a89683dd95, reversing
changes made to 2f1bd3f378.

compiler/rustc_driver_impl/src/lib.rs

@@ -1129,10 +1129,9 @@ fn get_backend_from_raw_matches(
     let backend_name = debug_flags
         .iter()
         .find_map(|x| x.strip_prefix("codegen-backend=").or(x.strip_prefix("codegen_backend=")));
-    let unstable_options = debug_flags.iter().find(|x| *x == "unstable-options").is_some();
     let target = parse_target_triple(early_dcx, matches);
     let sysroot = Sysroot::new(matches.opt_str("sysroot").map(PathBuf::from));
-    let target = config::build_target_config(early_dcx, &target, sysroot.path(), unstable_options);
+    let target = config::build_target_config(early_dcx, &target, sysroot.path());
 
     get_codegen_backend(early_dcx, &sysroot, backend_name, &target)
 }

compiler/rustc_interface/src/interface.rs

@@ -435,7 +435,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
         &early_dcx,
         &config.opts.target_triple,
         config.opts.sysroot.path(),
-        config.opts.unstable_opts.unstable_options,
     );
     let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
     let path_mapping = config.opts.file_path_mapping();

compiler/rustc_interface/src/tests.rs

@@ -46,7 +46,6 @@ fn sess_and_cfg<F>(args: &[&'static str], f: F)
         &early_dcx,
         &sessopts.target_triple,
         sessopts.sysroot.path(),
-        sessopts.unstable_opts.unstable_options,
     );
     let hash_kind = sessopts.unstable_opts.src_hash_algorithm(&target);
     let checksum_hash_kind = sessopts.unstable_opts.checksum_hash_algorithm();

compiler/rustc_session/src/config.rs

@@ -1589,9 +1589,8 @@ pub fn build_target_config(
     early_dcx: &EarlyDiagCtxt,
     target: &TargetTuple,
     sysroot: &Path,
-    unstable_options: bool,
 ) -> Target {
-    match Target::search(target, sysroot, unstable_options) {
+    match Target::search(target, sysroot) {
         Ok((target, warnings)) => {
             for warning in warnings.warning_messages() {
                 early_dcx.early_warn(warning)

compiler/rustc_session/src/session.rs

@@ -1002,11 +1002,8 @@ pub fn build_session(
     }
 
     let host_triple = TargetTuple::from_tuple(config::host_tuple());
-    let (host, target_warnings) =
-        Target::search(&host_triple, sopts.sysroot.path(), sopts.unstable_opts.unstable_options)
-            .unwrap_or_else(|e| {
-                dcx.handle().fatal(format!("Error loading host specification: {e}"))
-            });
+    let (host, target_warnings) = Target::search(&host_triple, sopts.sysroot.path())
+        .unwrap_or_else(|e| dcx.handle().fatal(format!("Error loading host specification: {e}")));
     for warning in target_warnings.warning_messages() {
         dcx.handle().warn(warning)
     }

compiler/rustc_target/src/spec/mod.rs

@@ -3296,19 +3296,10 @@ pub fn builtins() -> impl Iterator<Item = Target> {
     pub fn search(
         target_tuple: &TargetTuple,
         sysroot: &Path,
-        unstable_options: bool,
     ) -> Result<(Target, TargetWarnings), String> {
         use std::{env, fs};
 
-        fn load_file(
-            path: &Path,
-            unstable_options: bool,
-        ) -> Result<(Target, TargetWarnings), String> {
-            if !unstable_options {
-                return Err(
-                    "custom targets are unstable and require `-Zunstable-options`".to_string()
-                );
-            }
+        fn load_file(path: &Path) -> Result<(Target, TargetWarnings), String> {
             let contents = fs::read_to_string(path).map_err(|e| e.to_string())?;
             Target::from_json(&contents)
         }
@@ -3332,7 +3323,7 @@ fn load_file(
                 for dir in env::split_paths(&target_path) {
                     let p = dir.join(&path);
                     if p.is_file() {
-                        return load_file(&p, unstable_options);
+                        return load_file(&p);
                     }
                 }
 
@@ -3345,7 +3336,7 @@ fn load_file(
                     Path::new("target.json"),
                 ]);
                 if p.is_file() {
-                    return load_file(&p, unstable_options);
+                    return load_file(&p);
                 }
 
                 Err(format!("could not find specification for target {target_tuple:?}"))

tests/run-make/target-specs/rmake.rs

@@ -15,20 +15,11 @@ fn main() {
         .run_fail()
         .assert_stderr_contains("error loading target specification");
     rustc()
-        .arg("-Zunstable-options")
         .input("foo.rs")
         .target("my-incomplete-platform.json")
         .run_fail()
         .assert_stderr_contains("missing field `llvm-target`");
-    let test_platform = rustc()
-        .input("foo.rs")
-        .target("my-x86_64-unknown-linux-gnu-platform")
-        .crate_type("lib")
-        .emit("asm")
-        .run_fail()
-        .assert_stderr_contains("custom targets are unstable and require `-Zunstable-options`");
     rustc()
-        .arg("-Zunstable-options")
         .env("RUST_TARGET_PATH", ".")
         .input("foo.rs")
         .target("my-awesome-platform")
@@ -36,7 +27,6 @@ fn main() {
         .emit("asm")
         .run();
     rustc()
-        .arg("-Zunstable-options")
         .env("RUST_TARGET_PATH", ".")
         .input("foo.rs")
         .target("my-x86_64-unknown-linux-gnu-platform")
@@ -62,31 +52,27 @@ fn main() {
         .actual_text("test-platform-2", test_platform_2)
         .run();
     rustc()
-        .arg("-Zunstable-options")
         .input("foo.rs")
         .target("endianness-mismatch")
         .run_fail()
         .assert_stderr_contains(r#""data-layout" claims architecture is little-endian"#);
     rustc()
-        .arg("-Zunstable-options")
         .input("foo.rs")
         .target("mismatching-data-layout")
         .crate_type("lib")
         .run_fail()
         .assert_stderr_contains("data-layout for target");
     rustc()
-        .arg("-Zunstable-options")
         .input("foo.rs")
         .target("require-explicit-cpu")
         .crate_type("lib")
         .run_fail()
         .assert_stderr_contains("target requires explicitly specifying a cpu");
     rustc()
-        .arg("-Zunstable-options")
         .input("foo.rs")
         .target("require-explicit-cpu")
         .crate_type("lib")
         .arg("-Ctarget-cpu=generic")
         .run();
-    rustc().arg("-Zunstable-options").target("require-explicit-cpu").print("target-cpus").run();
+    rustc().target("require-explicit-cpu").arg("--print=target-cpus").run();
 }