[libc++] Add test to ensure that the mangling of types stays the same

[philnik777]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/143556.diff

1 Files Affected:

• (added) libcxx/test/libcxx/mangled_names.pass.cpp (+69)

diff --git a/libcxx/test/libcxx/mangled_names.pass.cpp b/libcxx/test/libcxx/mangled_names.pass.cpp
new file mode 100644
index 0000000000000..b74f08e95ffa4
--- /dev/null
+++ b/libcxx/test/libcxx/mangled_names.pass.cpp
@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Make sure that the mangling of our public types stays the same
+
+#include <cassert>
+#include <charconv>
+#include <iostream>
+#include <map>
+#include <typeinfo>
+#include <string_view>
+
+template <class>
+struct mangling {};
+
+struct test_struct {};
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+struct ns_mangling {};
+_LIBCPP_END_NAMESPACE_STD
+
+namespace std::__name {
+struct ns_mangling {};
+} // namespace std::__name
+
+namespace std::__long_name_to_make_sure_multiple_digits_work {
+struct ns_mangling {};
+} // namespace std::__long_name_to_make_sure_multiple_digits_work
+
+std::string get_std_inline_namespace_mangling(const std::type_info& info) {
+    std::string name = info.name();
+    assert(name.starts_with("NSt"));
+    unsigned name_len;
+    auto res = std::from_chars(name.data() + 3, name.data() + name.size(), name_len);
+    assert(res.ec == std::errc{});
+    return std::move(name).substr(0, (res.ptr + name_len) - name.data());
+}
+
+void expect_mangling(const std::type_info& info, std::string expected_name) {
+  if (expected_name != info.name())
+    std::__libcpp_verbose_abort("Expected: '%s'\n     Got: '%s'\n", expected_name.c_str(), info.name());
+}
+
+#define EXPECT_MANGLING(expected_mangling, ...) expect_mangling(typeid(__VA_ARGS__), expected_mangling)
+
+// Mangling names are really long, but splitting it up into multiple lines doesn't make it any more readable
+// clang-format off
+int main(int, char**) {
+  // self-test inline namespace recovery
+  assert(get_std_inline_namespace_mangling(typeid(std::__name::ns_mangling)) == "NSt6__name");
+  assert(get_std_inline_namespace_mangling(typeid(std::__long_name_to_make_sure_multiple_digits_work::ns_mangling)) == "NSt45__long_name_to_make_sure_multiple_digits_work");
+
+  // selftest
+  EXPECT_MANGLING("11test_struct", test_struct);
+
+  std::string ns_std = get_std_inline_namespace_mangling(typeid(std::ns_mangling));
+
+  // std::map
+  EXPECT_MANGLING(ns_std + "3mapIiiNS_4lessIiEENS_9allocatorINS_4pairIKiiEEEEEE", std::map<int, int>);
+  EXPECT_MANGLING(ns_std + "14__map_iteratorINS_15__tree_iteratorINS_12__value_typeIiiEEPNS_11__tree_nodeIS3_PvEElEEEE", std::map<int, int>::iterator);
+  EXPECT_MANGLING(ns_std + "20__map_const_iteratorINS_21__tree_const_iteratorINS_12__value_typeIiiEEPNS_11__tree_nodeIS3_PvEElEEEE", std::map<int, int>::const_iterator);
+
+  return 0;
+}

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[ldionne]

Suggested change

	// Make sure that the mangling of our public types stays the same
	// This test pins down the mangling of our public types to ensure that we don't
	// change it unintentionally, which is an ABI break.

[ldionne]

Is the plan to manually expand this to all public types in the library? That seems like something that'll quickly get out of hand and out of sync. I thought the idea was to create an automated test for this somehow (maybe clang-tidy?)

[philnik777]

At some point I'd like to add an automated test, yes. I'm not quite sure how to do that yet though.

For now my plan is to just pin down manglings where we think it's easy to mess up. I don't expect we'd miss a mangling change in most places, so I don't think it makes a ton of sense to add stuff like vector::iterator.