SERVER-42894 Create SourceLocation type and related macros

(cherry picked from commit a01e4d53caeb92cf07faa2507cefcfa8acbf017c)

4 files changed, 385 insertions, 0 deletions

diff --git a/src/mongo/platform/SConscript b/src/mongo/platform/SConscript
index 62805813b64..4d3daed97a5 100644
--- a/src/mongo/platform/SConscript
+++ b/src/mongo/platform/SConscript
@@ -11,6 +11,7 @@ env.CppUnitTest('endian_test', 'endian_test.cpp')
 env.CppUnitTest('mutex_test', 'mutex_test.cpp')
 env.CppUnitTest('process_id_test', 'process_id_test.cpp')
 env.CppUnitTest('random_test', 'random_test.cpp')
+env.CppUnitTest('source_location_test', 'source_location_test.cpp')
 env.CppUnitTest('stack_locator_test', 'stack_locator_test.cpp')
 env.CppUnitTest('decimal128_test', 'decimal128_test.cpp')
 env.CppUnitTest('decimal128_bson_test', 'decimal128_bson_test.cpp')
diff --git a/src/mongo/platform/source_location.h b/src/mongo/platform/source_location.h
new file mode 100644
index 00000000000..272029635cd
--- /dev/null
+++ b/src/mongo/platform/source_location.h
@@ -0,0 +1,158 @@
+/**
+ *    Copyright (C) 2019-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.
+ */
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+#if !defined(_MSC_VER) && !defined(__clang__)  // not windows or clang
+#include <experimental/source_location>
+#endif  // windows
+
+#include <fmt/format.h>
+
+namespace mongo {
+
+/**
+ * A SourceLocation is a constexpr type that captures a source location
+ *
+ * This class mimics the api signature of C++20 std::source_location
+ *
+ * It is intended to be constructed with MONGO_SOURCE_LOCATION() below.
+ */
+class SourceLocation {
+public:
+    constexpr SourceLocation(uint_least32_t line,
+                             uint_least32_t column,
+                             const char* file_name,
+                             const char* function_name) noexcept
+        : _line(line), _column(column), _file_name(file_name), _function_name(function_name) {}
+
+    constexpr uint_least32_t line() const noexcept {
+        return _line;
+    }
+
+    constexpr uint_least32_t column() const noexcept {
+        return _column;
+    }
+
+    constexpr const char* file_name() const noexcept {
+        return _file_name;
+    }
+
+    constexpr const char* function_name() const noexcept {
+        return _function_name;
+    }
+
+private:
+    uint_least32_t _line;
+    uint_least32_t _column;  // column will be 0 if there isn't compiler support
+    const char* _file_name;
+    const char* _function_name;
+};
+
+/**
+ * SourceLocationHolder is intended for convenient io of SourceLocation
+ */
+class SourceLocationHolder {
+public:
+    constexpr SourceLocationHolder(SourceLocation&& loc) noexcept
+        : _loc(std::forward<SourceLocation>(loc)) {}
+
+    constexpr uint_least32_t line() const noexcept {
+        return _loc.line();
+    }
+
+    constexpr uint_least32_t column() const noexcept {
+        return _loc.column();
+    }
+
+    constexpr const char* file_name() const noexcept {
+        return _loc.file_name();
+    }
+
+    constexpr const char* function_name() const noexcept {
+        return _loc.function_name();
+    }
+
+    std::string toString() const {
+        using namespace fmt::literals;
+        return R"({{fileName:"{}", line:{}, functionName:"{}"}})"_format(
+            _loc.file_name(), _loc.line(), _loc.function_name());
+    }
+
+    friend std::ostream& operator<<(std::ostream& out, const SourceLocationHolder& context) {
+        return out << context.toString();
+    }
+
+private:
+    SourceLocation _loc;
+};
+
+/**
+ * MONGO_SOURCE_LOCATION() either:
+ * - captures std::experimental::source_location::current()
+ * - makes a best effort with various macros and local static constants
+ *
+ * Since __FUNCSIG__ and __PRETTY_FUNCTION__ aren't defined outside of functions, there is also
+ * MONGO_SOURCE_LOCATION_NO_FUNC() for use with a default member initializatizer or constant
+ * initialization.
+ */
+#if defined(_MSC_VER)  // windows
+
+// MSVC does not have any of N4810 yet. (see
+// https://developercommunity.visualstudio.com/idea/354069/implement-c-library-fundamentals-ts-v2.html)
+#define MONGO_SOURCE_LOCATION() SourceLocation(__LINE__, 0ul, __FILE__, __func__)
+#define MONGO_SOURCE_LOCATION_NO_FUNC() SourceLocation(__LINE__, 0ul, __FILE__, "")
+
+#elif defined(__clang__)  // windows -> clang
+
+// Clang got __builtin_FILE et al as of 8.0.1 (see https://reviews.llvm.org/D37035)
+#define MONGO_SOURCE_LOCATION() SourceLocation(__LINE__, 0ul, __FILE__, __func__)
+#define MONGO_SOURCE_LOCATION_NO_FUNC() SourceLocation(__LINE__, 0ul, __FILE__, "")
+
+#elif defined(__GNUG__)  // clang -> gcc
+
+constexpr auto toSourceLocation(std::experimental::source_location loc) {
+    // Note that std::experimental::source_location captures __func__, not __PRETTY_FUNC__
+    return SourceLocation(loc.line(), loc.column(), loc.file_name(), loc.function_name());
+}
+
+#define MONGO_SOURCE_LOCATION() toSourceLocation(std::experimental::source_location::current())
+#define MONGO_SOURCE_LOCATION_NO_FUNC() \
+    toSourceLocation(std::experimental::source_location::current())
+
+#else  // gcc -> ?
+
+#error "Unknown compiler, cannot approximate std::source_location"
+
+#endif  // ?
+
+}  // namespace mongo
diff --git a/src/mongo/platform/source_location_test.cpp b/src/mongo/platform/source_location_test.cpp
new file mode 100644
index 00000000000..a702eda827e
--- /dev/null
+++ b/src/mongo/platform/source_location_test.cpp
@@ -0,0 +1,167 @@
+/**
+ *    Copyright (C) 2019-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 "mongo/platform/source_location_test.h"
+
+namespace mongo {
+namespace {
+
+constexpr SourceLocation makeLocalFunctionSourceLocationForTest() {
+    return MONGO_SOURCE_LOCATION();
+}
+
+const SourceLocationHolder kLocation = MONGO_SOURCE_LOCATION_NO_FUNC();
+
+struct StructWithDefaultInitContextMember {
+    const SourceLocationHolder location = MONGO_SOURCE_LOCATION_NO_FUNC();
+};
+
+#define CALL_MONGO_SOURCE_LOCATION() MONGO_SOURCE_LOCATION()
+
+TEST(SourceLocation, CorrectLineNumber) {
+    using LineT = std::invoke_result_t<decltype(&SourceLocation::line), SourceLocation>;
+    ASSERT_EQ(MONGO_SOURCE_LOCATION().line(), static_cast<LineT>(__LINE__));
+}
+
+TEST(SourceLocation, InlineVariable) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    SourceLocationHolder inlineLocation2 = MONGO_SOURCE_LOCATION();
+    SourceLocationHolder inlineLocation3 = MONGO_SOURCE_LOCATION();
+
+    // Each location should have the same filename
+    ASSERT_EQ(inlineLocation1.file_name(), inlineLocation2.file_name());
+    ASSERT_EQ(inlineLocation1.file_name(), inlineLocation3.file_name());
+
+    // The line numbers for each location should increase monotonically when inline
+    ASSERT_LT(inlineLocation1.line(), inlineLocation2.line());
+    ASSERT_LT(inlineLocation2.line(), inlineLocation3.line());
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << inlineLocation2;
+    unittest::log() << inlineLocation3;
+}
+
+TEST(SourceLocation, LocalFunction) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    SourceLocationHolder localFunctionLocation1 = makeLocalFunctionSourceLocationForTest();
+    SourceLocationHolder localFunctionLocation2 = makeLocalFunctionSourceLocationForTest();
+
+    // The inline location should have the same file name but a later line
+    ASSERT_EQ(inlineLocation1.file_name(), localFunctionLocation1.file_name());
+    ASSERT_GT(inlineLocation1.line(), localFunctionLocation1.line());
+
+    // The two local function locations should be identical
+    ASSERT_EQ(localFunctionLocation1, localFunctionLocation2);
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << localFunctionLocation1;
+    unittest::log() << localFunctionLocation2;
+}
+
+TEST(SourceLocation, HeaderFunction) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    SourceLocationHolder headerLocation1 = makeHeaderSourceLocationForTest();
+    SourceLocationHolder headerLocation2 = makeHeaderSourceLocationForTest();
+
+    // The inline location should have a different file name
+    ASSERT_NE(inlineLocation1.file_name(), headerLocation1.file_name());
+
+    // The two header locations should be identical
+    ASSERT_EQ(headerLocation1, headerLocation2);
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << headerLocation1;
+    unittest::log() << headerLocation2;
+}
+
+TEST(SourceLocation, GlobalVariable) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+
+    // The inline location should have the same file name but a later line
+    ASSERT_EQ(inlineLocation1.file_name(), kLocation.file_name());
+    ASSERT_GT(inlineLocation1.line(), kLocation.line());
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << kLocation;
+}
+
+TEST(SourceLocation, DefaultStructMember) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    StructWithDefaultInitContextMember obj1;
+    StructWithDefaultInitContextMember obj2;
+
+    // The inline location should have the same file name but a later line
+    ASSERT_EQ(inlineLocation1.file_name(), obj1.location.file_name());
+    ASSERT_GT(inlineLocation1.line(), obj1.location.line());
+
+    // The two default ctor'd struct member locations should be identical
+    ASSERT_EQ(obj1.location, obj2.location);
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << obj1.location;
+    unittest::log() << obj2.location;
+}
+
+TEST(SourceLocation, Macro) {
+    SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    SourceLocationHolder inlineLocation2 = CALL_MONGO_SOURCE_LOCATION();
+
+    // Each location should have the same filename
+    ASSERT_EQ(inlineLocation1.file_name(), inlineLocation2.file_name());
+
+    // The line numbers for each location should increase monotonically when inline
+    ASSERT_LT(inlineLocation1.line(), inlineLocation2.line());
+
+    unittest::log() << inlineLocation1;
+    unittest::log() << inlineLocation2;
+}
+
+TEST(SourceLocation, Constexpr) {
+    constexpr SourceLocationHolder inlineLocation1 = MONGO_SOURCE_LOCATION();
+    constexpr SourceLocationHolder inlineLocation2 = MONGO_SOURCE_LOCATION();
+    static_assert((inlineLocation1.line() + 1) == inlineLocation2.line());
+    static_assert(inlineLocation1.column() == inlineLocation2.column());
+    static_assert(areEqual(inlineLocation1.file_name(), inlineLocation2.file_name()));
+    static_assert(areEqual(inlineLocation1.function_name(), inlineLocation2.function_name()));
+
+    constexpr auto localFunctionLocation = makeLocalFunctionSourceLocationForTest();
+    static_assert(inlineLocation1.line() > localFunctionLocation.line());
+    static_assert(areEqual(inlineLocation1.file_name(), localFunctionLocation.file_name()));
+    static_assert(
+        !areEqual(inlineLocation1.function_name(), localFunctionLocation.function_name()));
+
+    constexpr auto headerLocation = makeHeaderSourceLocationForTest();
+    static_assert(!areEqual(inlineLocation1.file_name(), headerLocation.file_name()));
+    static_assert(!areEqual(inlineLocation1.function_name(), headerLocation.function_name()));
+}
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/platform/source_location_test.h b/src/mongo/platform/source_location_test.h
new file mode 100644
index 00000000000..4b97c72777e
--- /dev/null
+++ b/src/mongo/platform/source_location_test.h
@@ -0,0 +1,59 @@
+/**
+ *    Copyright (C) 2019-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.
+ */
+
+#pragma once
+
+#include "mongo/unittest/unittest.h"
+
+#include "mongo/platform/source_location.h"
+
+namespace mongo {
+inline bool operator==(const SourceLocationHolder& lhs, const SourceLocationHolder& rhs) {
+    return lhs.line() == rhs.line()            //
+        && lhs.column() == rhs.column()        //
+        && lhs.file_name() == rhs.file_name()  //
+        && lhs.function_name() == rhs.function_name();
+}
+
+inline bool operator!=(const SourceLocationHolder& lhs, const SourceLocationHolder& rhs) {
+    return !(lhs == rhs);
+}
+
+// Simple recursive constexpr string comparison to play nice with static_assert
+constexpr bool areEqual(const char* string1, const char* string2) {
+    return (string1 != nullptr)  //
+        && (string2 != nullptr)  //
+        && *string1 == *string2  //
+        && (*string1 == '\0' || areEqual(string1 + 1, string2 + 1));
+}
+
+inline constexpr SourceLocation makeHeaderSourceLocationForTest() {
+    return MONGO_SOURCE_LOCATION();
+}
+}  // namespace mongo