From a737f75a04317b3762db8e93c229d704a48e2d62 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=AE=B8=E6=9D=B0=E5=8F=8B=20Jieyou=20Xu=20=28Joe=29?=
 <39484203+jieyouxu@users.noreply.github.com>
Date: Tue, 22 Oct 2024 18:44:40 +0800
Subject: [PATCH] compiletest: conditionally build and provide `minicore` as
 extern prelude when requested via `//@ add-core-stubs` directive

`//@ add-core-stubs` will imply `-Cpanic=abort`.
---
 src/tools/compiletest/src/runtest.rs | 50 ++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index fff4f2df595..b337458f943 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -1150,14 +1150,20 @@ fn build_all_auxiliary(&self, of: &TestPaths, aux_dir: &Path, rustc: &mut Comman
         }
     }
 
-    /// `root_testpaths` refers to the path of the original test.
-    /// the auxiliary and the test with an aux-build have the same `root_testpaths`.
+    /// `root_testpaths` refers to the path of the original test. the auxiliary and the test with an
+    /// aux-build have the same `root_testpaths`.
     fn compose_and_run_compiler(
         &self,
         mut rustc: Command,
         input: Option<String>,
         root_testpaths: &TestPaths,
     ) -> ProcRes {
+        if self.props.add_core_stubs {
+            let minicore_path = self.build_minicore();
+            rustc.arg("--extern");
+            rustc.arg(&format!("minicore={}", minicore_path.to_str().unwrap()));
+        }
+
         let aux_dir = self.aux_output_dir();
         self.build_all_auxiliary(root_testpaths, &aux_dir, &mut rustc);
 
@@ -1171,6 +1177,37 @@ fn compose_and_run_compiler(
         )
     }
 
+    /// Builds `minicore`. Returns the path to the minicore rlib within the base test output
+    /// directory.
+    fn build_minicore(&self) -> PathBuf {
+        let output_file_path = self.output_base_dir().join("libminicore.rlib");
+        let mut rustc = self.make_compile_args(
+            &self.config.minicore_path,
+            TargetLocation::ThisFile(output_file_path.clone()),
+            Emit::None,
+            AllowUnused::Yes,
+            LinkToAux::No,
+            vec![],
+        );
+
+        rustc.args(&["--crate-type", "rlib"]);
+        rustc.arg("-Cpanic=abort");
+
+        let res =
+            self.compose_and_run(rustc, self.config.compile_lib_path.to_str().unwrap(), None, None);
+        if !res.status.success() {
+            self.fatal_proc_rec(
+                &format!(
+                    "auxiliary build of {:?} failed to compile: ",
+                    self.config.minicore_path.display()
+                ),
+                &res,
+            );
+        }
+
+        output_file_path
+    }
+
     /// Builds an aux dependency.
     fn build_auxiliary(
         &self,
@@ -1662,6 +1699,15 @@ fn make_compile_args(
 
         rustc.args(&self.props.compile_flags);
 
+        // FIXME(jieyouxu): we should report a fatal error or warning if user wrote `-Cpanic=` with
+        // something that's not `abort`, however, by moving this last we should override previous
+        // `-Cpanic=`s
+        //
+        // `minicore` requires `#![no_std]` and `#![no_core]`, which means no unwinding panics.
+        if self.props.add_core_stubs {
+            rustc.arg("-Cpanic=abort");
+        }
+
         rustc
     }