Auto merge of #127926 - Oneirical:classical-orctestra, r=<try>

Migrate `foreign-double-unwind`, `issue-36710` and `foreign-exceptions` `run-make` tests to rmake

Part of #121876 and the associated [Google Summer of Code project](https://blog.rust-lang.org/2024/05/01/gsoc-2024-selected-projects.html).

~~This is expected to fail CI, I am getting a weird `core dumped` error on `foreign-double-unwind` locally. Posting this to start a discussion.~~

EDIT: I got it, `foreign_double_unwind` is *supposed* to fail in the execution stage, but this wasn't obvious, because the original test was just piping the stdout to `CGREP` (which silently ignores errors).

try-job: aarch64-apple
try-job: armhf-gnu
try-job: test-various
try-job: x86_64-msvc
try-job: x86_64-gnu-llvm-18
try-job: i686-msvc

src/tools/run-make-support/src/external_deps/c_build.rs

@@ -1,12 +1,13 @@
 use std::path::PathBuf;
 
 use crate::artifact_names::static_lib_name;
-use crate::external_deps::cc::cc;
+use crate::external_deps::cc::{cc, cxx};
 use crate::external_deps::llvm::llvm_ar;
 use crate::path_helpers::path;
 use crate::targets::is_msvc;
 
 /// Builds a static lib (`.lib` on Windows MSVC and `.a` for the rest) with the given name.
+/// Built from a C file.
 #[track_caller]
 pub fn build_native_static_lib(lib_name: &str) -> PathBuf {
     let obj_file = if is_msvc() { format!("{lib_name}") } else { format!("{lib_name}.o") };
@@ -25,3 +26,24 @@ pub fn build_native_static_lib(lib_name: &str) -> PathBuf {
     llvm_ar().obj_to_ar().output_input(&lib_path, &obj_file).run();
     path(lib_path)
 }
+
+/// Builds a static lib (`.lib` on Windows MSVC and `.a` for the rest) with the given name.
+/// Built from a C++ file.
+#[track_caller]
+pub fn build_native_static_lib_cxx(lib_name: &str) -> PathBuf {
+    let obj_file = if is_msvc() { format!("{lib_name}") } else { format!("{lib_name}.o") };
+    let src = format!("{lib_name}.cpp");
+    let lib_path = static_lib_name(lib_name);
+    if is_msvc() {
+        cxx().arg("-EHs").arg("-c").out_exe(&obj_file).input(src).run();
+    } else {
+        cxx().arg("-c").out_exe(&obj_file).input(src).run();
+    };
+    let obj_file = if is_msvc() {
+        PathBuf::from(format!("{lib_name}.obj"))
+    } else {
+        PathBuf::from(format!("{lib_name}.o"))
+    };
+    llvm_ar().obj_to_ar().output_input(&lib_path, &obj_file).run();
+    path(lib_path)
+}

src/tools/run-make-support/src/external_deps/cc.rs

@@ -15,6 +15,12 @@ pub fn cc() -> Cc {
     Cc::new()
 }
 
+/// Construct a new platform-specific CXX compiler invocation.
+#[track_caller]
+pub fn cxx() -> Cc {
+    Cc::cxx()
+}
+
 /// A platform-specific C compiler invocation builder. The specific C compiler used is
 /// passed down from compiletest.
 #[derive(Debug)]
@@ -44,6 +50,21 @@ impl Cc {
         Self { cmd }
     }
 
+    /// Construct a new platform-specific C compiler invocation.
+    #[track_caller]
+    pub fn cxx() -> Self {
+        let compiler = env_var("CXX");
+
+        let mut cmd = Command::new(compiler);
+
+        let default_cflags = env_var("CXX_DEFAULT_FLAGS");
+        for flag in default_cflags.split(char::is_whitespace) {
+            cmd.arg(flag);
+        }
+
+        Self { cmd }
+    }
+
     /// Specify path of the input file.
     pub fn input<P: AsRef<Path>>(&mut self, path: P) -> &mut Self {
         self.cmd.arg(path.as_ref());
@@ -192,3 +213,41 @@ pub fn extra_cxx_flags() -> Vec<&'static str> {
         }
     }
 }
+
+/// `EXTRARSCXXFLAGS`
+pub fn extra_rs_cxx_flags() -> Vec<&'static str> {
+    // Adapted from tools.mk (trimmed):
+    //
+    // ```makefile
+    // ifdef IS_WINDOWS
+    //     ifdef IS_MSVC
+    //     else
+    //         EXTRARSCXXFLAGS := -lstatic:-bundle=stdc++
+    //     endif
+    // else
+    //     ifeq ($(UNAME),Darwin)
+    //         EXTRARSCXXFLAGS := -lc++
+    //     else
+    //         ifeq ($(UNAME),FreeBSD)
+    //         else
+    //             ifeq ($(UNAME),SunOS)
+    //             else
+    //                 ifeq ($(UNAME),OpenBSD)
+    //                 else
+    //                     EXTRARSCXXFLAGS := -lstdc++
+    //                 endif
+    //             endif
+    //         endif
+    //     endif
+    // endif
+    // ```
+    if is_windows() {
+        if is_msvc() { vec![] } else { vec!["-lstatic:-bundle=stdc++"] }
+    } else {
+        match &uname()[..] {
+            "Darwin" => vec!["-lc++"],
+            "FreeBSD" | "SunOS" | "OpenBSD" => vec![],
+            _ => vec!["-lstdc++"],
+        }
+    }
+}

src/tools/run-make-support/src/external_deps/rustc.rs

@@ -5,6 +5,7 @@ use crate::command::Command;
 use crate::env::env_var;
 use crate::path_helpers::cwd;
 use crate::util::set_host_rpath;
+use crate::{is_msvc, is_windows, uname};
 
 /// Construct a new `rustc` invocation. This will automatically set the library
 /// search path as `-L cwd()`. Use [`bare_rustc`] to avoid this.
@@ -314,4 +315,61 @@ impl Rustc {
         self.cmd.arg(format!("-Clinker-flavor={linker_flavor}"));
         self
     }
+
+    /// `EXTRARSCXXFLAGS`
+    pub fn extra_rs_cxx_flags(&mut self) -> &mut Self {
+        // Adapted from tools.mk (trimmed):
+        //
+        // ```makefile
+        // ifdef IS_WINDOWS
+        //     ifdef IS_MSVC
+        //     else
+        //         EXTRARSCXXFLAGS := -lstatic:-bundle=stdc++
+        //     endif
+        // else
+        //     ifeq ($(UNAME),Darwin)
+        //         EXTRARSCXXFLAGS := -lc++
+        //     else
+        //         ifeq ($(UNAME),FreeBSD)
+        //         else
+        //             ifeq ($(UNAME),SunOS)
+        //             else
+        //                 ifeq ($(UNAME),OpenBSD)
+        //                 else
+        //                     EXTRARSCXXFLAGS := -lstdc++
+        //                 endif
+        //             endif
+        //         endif
+        //     endif
+        // endif
+        // ```
+        let flag = if is_windows() {
+            // So this is a bit hacky: we can't use the DLL version of libstdc++ because
+            // it pulls in the DLL version of libgcc, which means that we end up with 2
+            // instances of the DW2 unwinding implementation. This is a problem on
+            // i686-pc-windows-gnu because each module (DLL/EXE) needs to register its
+            // unwind information with the unwinding implementation, and libstdc++'s
+            // __cxa_throw won't see the unwinding info we registered with our statically
+            // linked libgcc.
+            //
+            // Now, simply statically linking libstdc++ would fix this problem, except
+            // that it is compiled with the expectation that pthreads is dynamically
+            // linked as a DLL and will fail to link with a statically linked libpthread.
+            //
+            // So we end up with the following hack: we link use static:-bundle to only
+            // link the parts of libstdc++ that we actually use, which doesn't include
+            // the dependency on the pthreads DLL.
+            if is_msvc() { None } else { Some("-lstatic:-bundle=stdc++") }
+        } else {
+            match &uname()[..] {
+                "Darwin" => Some("-lc++"),
+                "FreeBSD" | "SunOS" | "OpenBSD" => None,
+                _ => Some("-lstdc++"),
+            }
+        };
+        if let Some(flag) = flag {
+            self.cmd.arg(flag);
+        }
+        self
+    }
 }

src/tools/run-make-support/src/lib.rs

@@ -43,7 +43,7 @@ pub use wasmparser;
 pub use external_deps::{c_build, cc, clang, htmldocck, llvm, python, rustc, rustdoc};
 
 // These rely on external dependencies.
-pub use c_build::build_native_static_lib;
+pub use c_build::{build_native_static_lib, build_native_static_lib_cxx};
 pub use cc::{cc, extra_c_flags, extra_cxx_flags, Cc};
 pub use clang::{clang, Clang};
 pub use htmldocck::htmldocck;

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -21,14 +21,11 @@ run-make/extern-fn-reachable/Makefile
 run-make/extern-multiple-copies/Makefile
 run-make/extern-multiple-copies2/Makefile
 run-make/fmt-write-bloat/Makefile
-run-make/foreign-double-unwind/Makefile
-run-make/foreign-exceptions/Makefile
 run-make/foreign-rust-exceptions/Makefile
 run-make/incr-add-rust-src-component/Makefile
 run-make/incr-foreign-head-span/Makefile
 run-make/interdependent-c-libraries/Makefile
 run-make/issue-35164/Makefile
-run-make/issue-36710/Makefile
 run-make/issue-47551/Makefile
 run-make/issue-69368/Makefile
 run-make/issue-84395-lto-embed-bitcode/Makefile

tests/run-make/cpp-global-destructors/rmake.rs

@@ -0,0 +1,27 @@
+// Some start files were missed when originally writing the logic to swap in musl start files.
+// This caused #36710. After the fix in #50105, this test checks that linking to C++ code
+// with global destructors works.
+// See https://github.com/rust-lang/rust/pull/50105
+
+//@ ignore-cross-compile
+// Reason: the compiled binary is executed
+
+// FIXME(Oneirical): are these really necessary? This test is supposed to test a musl
+// bug... and it ignores musl? This wasn't part of the original test at its creation, which
+// had no ignores.
+
+//# ignore-none no-std is not supported
+//# ignore-wasm32 FIXME: don't attempt to compile C++ to WASM
+//# ignore-wasm64 FIXME: don't attempt to compile C++ to WASM
+//# ignore-nvptx64-nvidia-cuda FIXME: can't find crate for `std`
+//# ignore-musl FIXME: this makefile needs teaching how to use a musl toolchain
+//#                    (see dist-i586-gnu-i586-i686-musl Dockerfile)
+//# ignore-sgx
+
+use run_make_support::{build_native_static_lib_cxx, run, rustc};
+
+fn main() {
+    build_native_static_lib_cxx("foo");
+    rustc().input("foo.rs").arg("-lfoo").extra_rs_cxx_flags().run();
+    run("foo");
+}

tests/run-make/foreign-double-unwind/rmake.rs

@@ -0,0 +1,21 @@
+// When using foreign function interface (FFI) with C++, it is possible
+// to run into a "double unwind" if either both Rust and C++ run into a panic
+// and exception at the same time, or C++ encounters two exceptions. In this case,
+// one of the panic unwinds would be leaked and the other would be kept, leading
+// to undefined behaviour. After this was fixed in #92911, this test checks that
+// the keyword "unreachable" indicative of this bug triggering in this specific context
+// does not appear after successfully compiling and executing the program.
+// See https://github.com/rust-lang/rust/pull/92911
+
+//@ needs-unwind
+// Reason: this test exercises panic unwinding
+//@ ignore-cross-compile
+// Reason: the compiled binary is executed
+
+use run_make_support::{build_native_static_lib_cxx, run_fail, rustc};
+
+fn main() {
+    build_native_static_lib_cxx("foo");
+    rustc().input("foo.rs").arg("-lfoo").extra_rs_cxx_flags().run();
+    run_fail("foo").assert_stdout_not_contains("unreachable");
+}

tests/run-make/foreign-exceptions/rmake.rs

@@ -0,0 +1,18 @@
+// This test was created to check that compilation and execution still works
+// after the addition of a new feature, in #65646: the ability to unwind panics
+// and exceptions back and forth between Rust and C++. Should this feature be broken,
+// the test should fail.
+// See https://github.com/rust-lang/rust/pull/65646
+
+//@ needs-unwind
+// Reason: this test exercises panic unwinding
+//@ ignore-cross-compile
+// Reason: the compiled binary is executed
+
+use run_make_support::{build_native_static_lib_cxx, run, rustc};
+
+fn main() {
+    build_native_static_lib_cxx("foo");
+    rustc().input("foo.rs").arg("-lfoo").extra_rs_cxx_flags().run();
+    run("foo");
+}