Port backtrace's line-tables-only test over to rustc

Author: jieyouxu

src/bootstrap/src/core/build_steps/test.rs

@@ -3159,6 +3159,7 @@ impl Step for TestHelpers {
             .opt_level(0)
             .warnings(false)
             .debug(false)
+            .flag("-g1")
             .file(builder.src.join("tests/auxiliary/rust_test_helpers.c"))
             .compile("rust_test_helpers");
     }

tests/auxiliary/rust_test_helpers.c

@@ -427,3 +427,18 @@ uint16_t issue_97463_leak_uninit_data(uint32_t a, uint32_t b, uint32_t c) {
 
     return data->b; /* leak data */
 }
+
+// Used for testing backtrace line_tables_only
+typedef void (*line_tables_only_callback) (void *data);
+
+void line_tables_only_baz(line_tables_only_callback cb, void *data) {
+    cb(data);
+}
+
+void line_tables_only_bar(line_tables_only_callback cb, void *data) {
+    line_tables_only_baz(cb, data);
+}
+
+void line_tables_only_foo(line_tables_only_callback cb, void *data) {
+    line_tables_only_bar(cb, data);
+}

tests/ui/debuginfo/backtrace-line-tables-only.rs

@@ -0,0 +1,56 @@
+// Test that when debug info only includes line tables that backtrace is still generated
+// successfully. This previously failed when compiling with `clang -g1`.
+// Part of <https://github.com/rust-lang/rust/issues/122899> porting some backtrace tests to rustc.
+// ignore-tidy-linelength
+//@ ignore-windows
+//@ run-pass
+//@ compile-flags: -Cdebuginfo=line-tables-only
+#![feature(backtrace_frames)]
+
+use std::backtrace::{self, Backtrace};
+use std::ffi::c_void;
+use std::ptr::addr_of_mut;
+
+pub type Callback = extern "C" fn(data: *mut c_void);
+
+#[link(name = "rust_test_helpers", kind = "static")]
+extern "C" {
+    pub fn line_tables_only_foo(cb: Callback, data: *mut c_void);
+}
+
+extern "C" fn store_backtrace(data: *mut c_void) {
+    let bt = backtrace::Backtrace::capture();
+    unsafe { *data.cast::<Option<Backtrace>>() = Some(bt) };
+}
+
+fn assert_contains(
+    backtrace: &Backtrace,
+    expected_name: &str,
+    expected_file: &str,
+    expected_line: u32,
+) {
+    // FIXME(jieyouxu): fix this ugly fragile test when `BacktraceFrame` has accessors like...
+    // `symbols()`.
+    let backtrace = format!("{:#?}", backtrace);
+    eprintln!("{}", backtrace);
+    assert!(backtrace.contains(expected_name), "backtrace does not contain expected name {}", expected_name);
+    assert!(backtrace.contains(expected_file), "backtrace does not contain expected file {}", expected_file);
+    assert!(backtrace.contains(&expected_line.to_string()), "backtrace does not contain expected line {}", expected_line);
+}
+
+/// Verifies that when debug info includes only lines tables the generated
+/// backtrace is still generated successfully. The test exercises behaviour
+/// that failed previously when compiling with clang -g1.
+///
+/// The test case uses C rather than rust, since at that time when it was
+/// written the debug info generated at level 1 in rustc was essentially
+/// the same as at level 2.
+fn main() {
+    std::env::set_var("RUST_BACKTRACE", "1");
+    let mut backtrace: Option<Backtrace> = None;
+    unsafe { line_tables_only_foo(store_backtrace, addr_of_mut!(backtrace).cast::<c_void>()) };
+    let backtrace = backtrace.expect("backtrace");
+    assert_contains(&backtrace, "line_tables_only_foo", "rust_test_helpers.c", 435);
+    assert_contains(&backtrace, "line_tables_only_bar", "rust_test_helpers.c", 439);
+    assert_contains(&backtrace, "line_tables_only_baz", "rust_test_helpers.c", 443);
+}