Auto merge of rust-lang#136695 - jieyouxu:cpp_smoke_test, r=<try>

Port `rust-lang/backtrace`'s `cpp_smoke_test` to `rust-lang/rust` test suite

Ports https://github.com/rust-lang/backtrace-rs/tree/e33eaac8caf46d0d3cc57f8d152529e8b7ae1b78/crates/cpp_smoke_test to the main repo.

I can't say I'm 100% convinced by the value of this test living in the main repo for several reasons:

1. This test (or at least the actual `cpp_smoke_test.rs` is **extremely** fragile. It's sensitive to debuginfo levels AND optimizations. On `x86_64-unknown-linux-gnu`, the C++ file **must** be compiled with **exactly** `-O1`. No more, no less, or else the backtrace symbol names do not line up in symbol count or name.
2. I could not get this test to work on Windows MSVC, no matter which combination of debuginfo levels and optimization levels I tried.

Note that I have not tried other targets, e.g. Apple friends, which may fail for yet other reasons.

Possibly supersedes rust-lang#136182.

r? `@ChrisDenton` (or `@workingjubilee)`

try-job: x86_64-apple-1
try-job: aarch64-apple

Author: bors

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

@@ -6,7 +6,8 @@ use crate::external_deps::llvm::llvm_ar;
 use crate::path_helpers::path;
 use crate::targets::{is_darwin, is_msvc, is_windows};
 
-// FIXME(Oneirical): These native build functions should take a Path-based generic.
+// FIXME(jieyouxu): figure out a way to improve the usability of these helpers... They are really
+// messy.
 
 /// Builds a static lib (`.lib` on Windows MSVC and `.a` for the rest) with the given name.
 /// Built from a C file.
@@ -75,8 +76,8 @@ pub fn build_native_dynamic_lib(lib_name: &str) -> PathBuf {
     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.
+/// Builds a static lib (`.lib` on Windows MSVC and `.a` for the rest) with the given name. Built
+/// from a C++ file. Unoptimized.
 #[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") };
@@ -95,3 +96,35 @@ pub fn build_native_static_lib_cxx(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. Optimized with the provided `opt_level` flag. Note that the `opt_level_flag`
+/// can differ between different C++ compilers! Consult relevant docs for `g++`/`clang++`/MSVC.
+#[track_caller]
+pub fn build_native_static_lib_cxx_optimized(lib_name: &str, opt_level_flag: &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);
+
+    // NOTE: generate debuginfo
+    if is_msvc() {
+        cxx()
+            .arg(opt_level_flag)
+            .arg("-Zi")
+            .arg("-debug")
+            .arg("-EHs")
+            .arg("-c")
+            .out_exe(&obj_file)
+            .input(src)
+            .run();
+    } else {
+        cxx().arg(opt_level_flag).arg("-g").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/lib.rs

@@ -37,6 +37,7 @@ pub mod rfs {
 // Re-exports of third-party library crates.
 // tidy-alphabetical-start
 pub use bstr;
+pub use cc as crate_cc; // NOTE: aliased to avoid being confused with `c_cxx_compiler::cc`.
 pub use gimli;
 pub use libc;
 pub use object;
@@ -55,7 +56,7 @@ pub use external_deps::{
 pub use c_cxx_compiler::{Cc, Gcc, cc, cxx, extra_c_flags, extra_cxx_flags, gcc};
 pub use c_build::{
     build_native_dynamic_lib, build_native_static_lib, build_native_static_lib_cxx,
-    build_native_static_lib_optimized,
+    build_native_static_lib_optimized, build_native_static_lib_cxx_optimized,
 };
 pub use cargo::cargo;
 pub use clang::{clang, Clang};

tests/run-make/cpp-smoke-test/cpp_smoke_test.rs

@@ -0,0 +1,72 @@
+extern crate backtrace;
+
+use std::sync::atomic::{AtomicBool, Ordering};
+
+unsafe extern "C" {
+    unsafe fn cpp_trampoline(func: extern "C" fn());
+}
+
+fn main() {
+    static RAN_ASSERTS: AtomicBool = AtomicBool::new(false);
+
+    extern "C" fn assert_cpp_frames() {
+        let mut physical_frames = Vec::new();
+        backtrace::trace(|cx| {
+            physical_frames.push(cx.ip());
+
+            // We only want to capture:
+            //
+            // 1. this closure's frame
+            // 2. `assert_cpp_frames`,
+            // 3. `space::templated_trampoline`, and
+            // 4. `cpp_trampoline`.
+            //
+            // Those are logical frames, which might be inlined into fewer physical frames, so we
+            // may end up with extra logical frames after resolving these.
+            physical_frames.len() < 4
+        });
+
+        let names: Vec<_> = physical_frames
+            .into_iter()
+            .flat_map(|ip| {
+                let mut logical_frame_names = vec![];
+
+                backtrace::resolve(ip, |sym| {
+                    let sym_name = sym.name().expect("Should have a symbol name");
+                    let demangled = sym_name.to_string();
+                    logical_frame_names.push(demangled);
+                });
+
+                assert!(
+                    !logical_frame_names.is_empty(),
+                    "Should have resolved at least one symbol for the physical frame"
+                );
+
+                logical_frame_names
+            })
+            // Skip the backtrace::trace closure and assert_cpp_frames, and then
+            // take the two C++ frame names.
+            .skip_while(|name| !name.contains("trampoline"))
+            .take(2)
+            .collect();
+
+        println!("actual names = {names:#?}");
+
+        let expected =
+            ["void space::templated_trampoline<void (*)()>(void (*)())", "cpp_trampoline"];
+        println!("expected names = {expected:#?}");
+
+        assert_eq!(names.len(), expected.len());
+        for (actual, expected) in names.iter().zip(expected.iter()) {
+            assert_eq!(actual, expected);
+        }
+
+        RAN_ASSERTS.store(true, Ordering::SeqCst);
+    }
+
+    assert!(!RAN_ASSERTS.load(Ordering::SeqCst));
+    unsafe {
+        cpp_trampoline(assert_cpp_frames);
+    }
+    assert!(RAN_ASSERTS.load(Ordering::SeqCst));
+}

tests/run-make/cpp-smoke-test/rmake.rs

@@ -0,0 +1,65 @@
+//! `backtrace`'s `cpp_smoke_test` ported to rust-lang/rust.
+//!
+//! A basic smoke test that exercises `backtrace` to see if it can resolve basic C++ templated +
+//! trampolined symbol names.
+
+//@ ignore-cross-compile (binary needs to run)
+//@ only-nightly
+
+//@ ignore-windows-msvc (test fails due to backtrace symbol mismatches)
+// FIXME: on MSVC, at `-O1`, there are no symbols available. At `-O0`, the test fails looking like:
+// ```
+// actual names = [
+//     "space::templated_trampoline<void (__cdecl*)(void)>",
+// ]
+// expected names = [
+//     "void space::templated_trampoline<void (*)()>(void (*)())",
+//     "cpp_trampoline",
+// ]
+// ```
+
+use run_make_support::rustc::sysroot;
+use run_make_support::{
+    build_native_static_lib_cxx_optimized, cargo, crate_cc, cwd, path, rfs, run, rustc,
+    source_root, target,
+};
+
+fn main() {
+    let target_dir = path("target");
+    let src_root = source_root();
+    let backtrace_submodule = src_root.join("library").join("backtrace");
+    let backtrace_toml = backtrace_submodule.join("Cargo.toml");
+
+    // Build the `backtrace` package (the `library/backtrace` submodule to make sure we exercise the
+    // same `backtrace` as shipped with std).
+    cargo()
+        // NOTE: needed to skip trying to link in `windows.0.52.0.lib` which is pre-built but not
+        // available in *this* scenario.
+        .env("RUSTFLAGS", "--cfg=windows_raw_dylib")
+        .arg("build")
+        .args(&["--manifest-path", &backtrace_toml.to_str().unwrap()])
+        .args(&["--target", &target()])
+        .arg("--features=cpp_demangle")
+        .env("CARGO_TARGET_DIR", &target_dir)
+        // Visual Studio 2022 requires that the LIB env var be set so it can
+        // find the Windows SDK.
+        .env("LIB", std::env::var("LIB").unwrap_or_default())
+        .run();
+
+    let rlibs_path = target_dir.join(target()).join("debug").join("deps");
+
+    // FIXME: this test is *really* fragile. Even on `x86_64-unknown-linux-gnu`, this fails if a
+    // different opt-level is passed. On `-O2` this test fails due to no symbols found. On `-O0`
+    // this test fails because it's missing one of the expected symbols.
+    build_native_static_lib_cxx_optimized("trampoline", "-O1");
+
+    rustc()
+        .input("cpp_smoke_test.rs")
+        .library_search_path(&rlibs_path)
+        .library_search_path(cwd())
+        .debuginfo("2")
+        .arg("-ltrampoline")
+        .run();
+
+    run("cpp_smoke_test");
+}

tests/run-make/cpp-smoke-test/trampoline.cpp

@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+namespace space {
+    template <typename FuncT>
+    void templated_trampoline(FuncT func) {
+        func();
+    }
+}
+
+typedef void (*FuncPtr)();
+
+extern "C" void cpp_trampoline(FuncPtr func) {
+    space::templated_trampoline(func);
+}