SERVER-33259 add libunwind to third_party

2 files changed, 149 insertions, 0 deletions

diff --git a/src/mongo/base/SConscript b/src/mongo/base/SConscript
index 7929eb27bfc..dd9f19eb95b 100644
--- a/src/mongo/base/SConscript
+++ b/src/mongo/base/SConscript
@@ -105,3 +105,19 @@ env.CppUnitTest(
         'system_error',
     ],
 )
+
+# To be enabled by a '--enable-libunwind' option coming soon.
+if False:
+    unwindTestEnv = env.Clone()
+    unwindTestEnv.InjectThirdParty(libraries=['unwind'])
+    unwindTestEnv.CppUnitTest(
+        target=[
+            'unwind_test',
+        ],
+        source=[
+            'unwind_test.cpp',
+        ],
+        LIBDEPS=[
+            '$BUILD_DIR/third_party/shim_unwind',
+        ]
+    )
diff --git a/src/mongo/base/unwind_test.cpp b/src/mongo/base/unwind_test.cpp
new file mode 100644
index 00000000000..2e64a586889
--- /dev/null
+++ b/src/mongo/base/unwind_test.cpp
@@ -0,0 +1,133 @@
+/**
+ *    Copyright (C) 2018-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <cxxabi.h>
+#include <sstream>
+
+#include <fmt/format.h>
+#include <fmt/printf.h>
+
+#include <libunwind.h>
+
+#include "mongo/stdx/functional.h"
+#include "mongo/unittest/unittest.h"
+#include "mongo/util/if_constexpr.h"
+
+namespace mongo {
+
+// Must be a named namespace so the functions we want to unwind through have external linkage.
+// Without that, the compiler optimizes them away.
+namespace unwind_test_detail {
+
+using namespace fmt::literals;
+
+std::string trace() {
+    std::string out;
+    unw_cursor_t cursor;
+    unw_context_t context;
+
+    // Initialize cursor to current frame for local unwinding.
+    unw_getcontext(&context);
+    unw_init_local(&cursor, &context);
+    // Unwind frames one by one, going up the frame stack.
+    while (unw_step(&cursor) > 0) {
+        unw_word_t offset, pc;
+        unw_get_reg(&cursor, UNW_REG_IP, &pc);
+        if (pc == 0) {
+            break;
+        }
+        out += "0x{:x}:"_format(pc);
+        char sym[32 << 10];
+        char* name = sym;
+        int err;
+        if ((err = unw_get_proc_name(&cursor, sym, sizeof(sym), &offset)) != 0) {
+            out += " -- error: unable to obtain symbol name for this frame: {:d}\n"_format(err);
+            continue;
+        }
+        name = sym;
+        int status;
+        char* demangled_name;
+        if ((demangled_name = abi::__cxa_demangle(sym, nullptr, nullptr, &status))) {
+            name = demangled_name;
+        }
+        out += " ({:s}+0x{:x})\n"_format(name, offset);
+        if (name != sym) {
+            free(name);  // allocated by abi::__cxa_demangle
+        }
+    }
+    return out;
+}
+
+struct Context {
+    std::vector<stdx::function<void(Context&)>> plan;
+    std::string s;
+};
+
+// Disable clang-format for the "if constexpr"
+template <int N>
+void callNext(Context& ctx) {
+    IF_CONSTEXPR (N == 0) {
+        ctx.s = trace();
+    } else {
+        ctx.plan[N - 1](ctx);
+    }
+    // Forces compiler to invoke next plan with `call` instead of `jmp`.
+    asm volatile("");  // NOLINT
+}
+
+TEST(Unwind, Demangled) {
+    // Trickery with std::vector<stdx::function> is to hide from the optimizer.
+    Context ctx{{
+        callNext<0>, callNext<1>, callNext<2>, callNext<3>, callNext<4>, callNext<5>,
+    }};
+    ctx.plan.back()(ctx);
+    // Check that these function names appear in the trace, in order.
+    // There will of course be characters between them but ignore that.
+    const std::string frames[] = {
+        "void mongo::unwind_test_detail::callNext<0>(mongo::unwind_test_detail::Context&)",
+        "void mongo::unwind_test_detail::callNext<1>(mongo::unwind_test_detail::Context&)",
+        "void mongo::unwind_test_detail::callNext<2>(mongo::unwind_test_detail::Context&)",
+        "void mongo::unwind_test_detail::callNext<3>(mongo::unwind_test_detail::Context&)",
+        "void mongo::unwind_test_detail::callNext<4>(mongo::unwind_test_detail::Context&)",
+        "void mongo::unwind_test_detail::callNext<5>(mongo::unwind_test_detail::Context&)",
+        "main",
+    };
+    size_t pos = 0;
+    for (const auto& expected : frames) {
+        pos = ctx.s.find(expected, pos);
+        ASSERT_NE(pos, ctx.s.npos) << ctx.s;
+    }
+}
+
+}  // namespace unwind_test_detail
+}  // namespace mongo