Upgrade the build to require C++20

BUILD.md

@@ -8,7 +8,7 @@ This guide describes how to build **MMapper** from source on Linux, macOS, and W
 
 Ensure the following tools are installed:
 
-- A C++17-compatible compiler (e.g., GCC, Clang, MSVC)
+- A C++20-compatible compiler (e.g., GCC 11+, Clang 16+, MSVC 19.29+)
 - [CMake 3.20+](https://cmake.org/)
 - [Ninja](https://ninja-build.org/)
 - [Qt 6.4+](https://www.qt.io/) (6.5 recommended) with `QtWebSockets` and `QtMultimedia`

CMakeLists.txt

@@ -3,7 +3,7 @@ project(mmapper CXX)
 
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
@@ -461,7 +461,7 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         add_compile_options(-Werror=shorten-64-to-32)
         add_compile_options(-Werror=sign-conversion) # can warn about hard-to-spot bugs.
         add_compile_options(-Werror=switch)
-        add_compile_options(-Werror=unused-result) # required for c++17 [[nodiscard]]
+        add_compile_options(-Werror=unused-result) # required for [[nodiscard]]
         add_compile_options(-Werror=weak-vtables) # can result in crashes for ODR violations.
 
         # remove noise (most of these cannot be fixed)
@@ -472,6 +472,7 @@ if(MSVC)
     add_definitions(-DNOMINMAX)
     # modernize the __cplusplus value
     add_compile_options(/Zc:__cplusplus)
+    add_compile_options(/Zc:preprocessor)
     add_compile_options(/utf-8)
     add_compile_options(/permissive-)
     if(CMAKE_BUILD_TYPE_UPPER MATCHES "^RELWITHDEBINFO$")

iwyu-mapping-stl.imp

@@ -6,7 +6,7 @@
  {include: ["<bits/stdint-uintn.h>", private, "<cstdint>", public]},
  {include: ["<bits/unique_ptr.h>", private, "<memory>", public]},
 
- # NOTE: this <cmath> is the correct header for std::abs() in c++17
+ # NOTE: this <cmath> is the correct header for std::abs() in C++20
  {include: ["<bits/std_abs.h>", private, "<cstdlib>", public]},
 
  {include: ["<assert.h>", public, "<cassert>", public]},

src/CMakeLists.txt

@@ -771,7 +771,7 @@ endif()
 
 set_target_properties(
   mmapper PROPERTIES
-  CXX_STANDARD 17
+  CXX_STANDARD 20
   CXX_STANDARD_REQUIRED ON
   CXX_EXTENSIONS OFF
   COMPILE_FLAGS "${WARNING_FLAGS}"
@@ -781,15 +781,15 @@ set_target_properties(
 
 set_target_properties(
   mm_global PROPERTIES
-  CXX_STANDARD 17
+  CXX_STANDARD 20
   CXX_STANDARD_REQUIRED ON
   CXX_EXTENSIONS OFF
   COMPILE_FLAGS "${WARNING_FLAGS}"
 )
 
 set_target_properties(
   mm_map PROPERTIES
-  CXX_STANDARD 17
+  CXX_STANDARD 20
   CXX_STANDARD_REQUIRED ON
   CXX_EXTENSIONS OFF
   COMPILE_FLAGS "${WARNING_FLAGS}"

src/global/AnsiOstream.h

@@ -135,6 +135,10 @@ class NODISCARD AnsiOstream final
     void write(char16_t codepoint);
     void write(char32_t codepoint);
     void write(std::string_view sv);
+    void write(std::u8string_view sv)
+    {
+        write(std::string_view{reinterpret_cast<const char *>(sv.data()), sv.size()});
+    }
 
     template<typename T>
     auto write(const T n)

src/global/AnsiTextUtils.h

@@ -995,7 +995,11 @@ void foreachAnsi(const QStringView line, Callback &&callback)
     const auto len = line.size();
     qsizetype pos = 0;
     while (pos < len) {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        QRegularExpressionMatch m = weakAnsiRegex.matchView(line, pos);
+#else
         QRegularExpressionMatch m = weakAnsiRegex.match(line, pos);
+#endif
         if (!m.hasMatch()) {
             break;
         }

src/global/Charset-Utf8.cpp

@@ -552,13 +552,7 @@ NODISCARD static constexpr bool is7bit(const char c) noexcept
 }
 NODISCARD static constexpr bool is7bit(const std::string_view sv) noexcept
 {
-    // NOLINTNEXTLINE (can't use std::all_of() in constexpr in c++17)
-    for (const char c : sv) {
-        if (!is7bit(c)) {
-            return false;
-        }
-    }
-    return true;
+    return std::all_of(sv.begin(), sv.end(), [](char c) { return is7bit(c); });
 }
 
 NODISCARD static constexpr Utf8ValidationEnum validateUtf8(std::string_view sv) noexcept

src/global/Charset.cpp

@@ -348,7 +348,6 @@ ALLOW_DISCARD QString &toAsciiInPlace(QString &str)
 
     // NOTE: 128 (0x80) was not converted to 'z' before.
     for (QChar &qc : str) {
-        // c++17 if statement with initializer
         if (const char ch = mmqt::toLatin1(qc); !isAscii(ch)) {
             qc = QLatin1Char{charset::conversion::latin1ToAscii(ch)};
         }

src/global/emojis.cpp

@@ -172,20 +172,28 @@ struct NODISCARD Emojis final
     {
     private:
 #if defined(__cpp_lib_generic_unordered_lookup) && __cpp_lib_generic_unordered_lookup
-        static_assert(false, "Not tested; this may need to be fixed.");
-        using HashBase = std::hash<std::u32string_view>;
-        struct NODISCARD Hash final : public HashBase
+        struct NODISCARD Hash final
         {
-            auto operator()(const std::u32string &s) const { return HashBase::operator()(s); }
+            using is_transparent = void;
+            size_t operator()(const std::u32string &s) const
+            {
+                return std::hash<std::u32string>{}(s);
+            }
+            size_t operator()(std::u32string_view sv) const
+            {
+                return std::hash<std::u32string_view>{}(sv);
+            }
         };
         struct NODISCARD Pred final
         {
-            using T1 = const std::u32string &;
-            using T2 = const std::u32string_view;
-            bool operator()(T1 a, T1 b) const { return a == b; }
-            bool operator()(T1 a, T2 b) const { return a == b; }
-            bool operator()(T2 a, T1 b) const { return a == b; }
-            // bool operator()(T2 a, T2 b) const { return a == b; }
+            using is_transparent = void;
+            bool operator()(const std::u32string &a, const std::u32string &b) const
+            {
+                return a == b;
+            }
+            bool operator()(const std::u32string &a, std::u32string_view b) const { return a == b; }
+            bool operator()(std::u32string_view a, const std::u32string &b) const { return a == b; }
+            bool operator()(std::u32string_view a, std::u32string_view b) const { return a == b; }
         };
         using Map = std::unordered_map<std::u32string, std::optional<std::u32string>, Hash, Pred>;
 #else
@@ -604,7 +612,7 @@ NODISCARD QString mmqt::encodeEmojiShortCodes(const QString &s)
 
             // REVISIT: should this include "U+" or not?
             char hex[32];
-            snprintf(hex, sizeof(hex), "[:U+%X:]", c);
+            snprintf(hex, sizeof(hex), "[:U+%X:]", static_cast<unsigned int>(c));
             for (const char ascii : std::string_view{hex}) {
                 m_output += static_cast<char32_t>(static_cast<uint8_t>(ascii));
             }

src/global/float_cast.h

@@ -28,33 +28,29 @@ NODISCARD constexpr bool isSameIntValue(const A a, const B b) noexcept
     return a == b;
 }
 
-// This only exists because c++17 std::isnan() is not constexpr;
-// using "f != f" feels like a hack.
 template<typename FloatType>
 NODISCARD constexpr bool isNan(const FloatType f) noexcept
 {
-#if __cplusplus >= 202000L
+#if defined(__cpp_lib_constexpr_cmath) && __cpp_lib_constexpr_cmath >= 202202L
     return std::isnan(f);
+#elif defined(__clang__) || defined(__GNUC__)
+    return __builtin_isnan(f);
 #else
-#ifdef __clang__
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wfloat-equal"
-#endif
-    return f != f; // NOLINT (this is only true for NaNs)
-#ifdef __clang__
-#pragma clang diagnostic pop
-#endif
+    // std::isnan() is not constexpr in all C++20 implementations (e.g. MSVC 2022)
+    return f != f;
 #endif
 }
 
-// this only exists because c++17 std::isfinite() is not constexpr
 template<typename FloatType>
 NODISCARD constexpr bool isFinite(const FloatType f) noexcept
 {
-#if __cplusplus >= 202000L
+#if defined(__cpp_lib_constexpr_cmath) && __cpp_lib_constexpr_cmath >= 202202L
     return std::isfinite(f);
+#elif defined(__clang__) || defined(__GNUC__)
+    return __builtin_isfinite(f);
 #else
-    constexpr auto inf = std::numeric_limits<FloatType>::infinity();
+    // std::isfinite() is not constexpr in all C++20 implementations (e.g. MSVC 2022)
+    const auto inf = std::numeric_limits<FloatType>::infinity();
     return !isNan(f) && -inf < f && f < inf;
 #endif
 }

src/global/mm_source_location.h

@@ -4,28 +4,17 @@
 
 #include "macros.h"
 
-#include <cstdint>
-
-#if __cplusplus >= 202000L \
-    && __has_builtin(__builtin_source_location) // && __cpp_lib_source_location >= 201907L
 #include <source_location>
+
 namespace mm {
+/*
+ * NOTE: std::source_location (C++20) support:
+ * - GCC 11+
+ * - Clang 16+
+ * - MSVC 19.29+ (Visual Studio 2019 16.11+)
+ * - Apple Clang 15+ (macOS 14+)
+ */
 using source_location = std::source_location;
-}
-#define MM_SOURCE_LOCATION() (std::source_location::current())
-#else
-namespace mm {
-// TODO: replace this with C++20's std::source_location
-struct NODISCARD source_location final
-{
-    const char *m_file_name = "";
-    const char *m_function_name = "";
-    std::uint_least32_t m_line = 0;
-
-    NODISCARD const char *file_name() const { return this->m_file_name; }
-    NODISCARD const char *function_name() const { return this->m_function_name; }
-    NODISCARD std::uint_least32_t line() const { return this->m_line; }
-};
 } // namespace mm
-#define MM_SOURCE_LOCATION() (mm::source_location{__FILE__, __FUNCTION__, __LINE__})
-#endif
+
+#define MM_SOURCE_LOCATION() (std::source_location::current())

src/global/utils.h

@@ -411,16 +411,7 @@ ALLOW_DISCARD static inline size_t erase_if(Container &container, Callback &&cal
 template<typename T, typename Predicate>
 NODISCARD bool listRemoveIf(std::list<T> &list, Predicate &&should_remove)
 {
-    // c++20 version of remove_if() returns # of elements removed, but c++17 doesn't.
-    bool removed = false;
-    list.remove_if([&removed, &should_remove](const T &element) -> bool {
-        if (should_remove(element)) {
-            removed = true;
-            return true;
-        }
-        return false;
-    });
-    return removed;
+    return std::erase_if(list, std::forward<Predicate>(should_remove)) > 0;
 }
 
 template<typename Container, typename Callback>
@@ -449,9 +440,8 @@ NODISCARD static inline auto find_min_computed(const Container &container, Callb
     }
 }
 
-// This can be removed and replaced with std::remove_cvref_t<T> in c++20.
 template<typename T>
-using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;
+using remove_cvref_t = std::remove_cvref_t<T>;
 
 template<typename T, typename... Ts>
 struct are_distinct : std::conjunction<std::negation<std::is_same<T, Ts>>..., are_distinct<Ts...>>

src/map/ExitFields.h

@@ -8,6 +8,9 @@
 struct NODISCARD ExitFields final : public ExitFieldsGetters<ExitFields>,
                                     public ExitFieldsSetters<ExitFields>
 {
+public:
+    ExitFields() {}
+
 public:
 #define X_DECL_FIELD(_Type, _Prop, _OptInit) _Type _Prop _OptInit;
     XFOREACH_EXIT_PROPERTY(X_DECL_FIELD)

src/map/RawExit.h

@@ -13,6 +13,9 @@ template<typename Tag_>
 struct NODISCARD TaggedRawExit final : public ExitFieldsGetters<TaggedRawExit<Tag_>>,
                                        public ExitFieldsSetters<TaggedRawExit<Tag_>>
 {
+public:
+    TaggedRawExit() {}
+
 public:
     using IdType = std::conditional_t<
         std::is_same_v<Tag_, ::tags::RoomIdTag>,

src/map/RawRoom.h

@@ -15,6 +15,9 @@ struct NODISCARD TaggedRawRoom final : public RoomFieldsGetters<TaggedRawRoom<Ta
                                        public RoomFieldsSetters<TaggedRawRoom<Tag_>>,
                                        public RoomExitFieldsSetters<TaggedRawRoom<Tag_>>
 {
+public:
+    TaggedRawRoom() {}
+
 public:
     using ExitType = TaggedRawExit<Tag_>;
     using IdType = typename ExitType::IdType;

src/map/RoomFields.h

@@ -10,6 +10,9 @@
 struct NODISCARD RoomFields final : public RoomFieldsGetters<RoomFields>,
                                     public RoomFieldsSetters<RoomFields>
 {
+public:
+    RoomFields() {}
+
 public:
 #define X_DECL_FIELD(_Type, _Prop, _OptInit) _Type _Prop{_OptInit};
     XFOREACH_ROOM_PROPERTY(X_DECL_FIELD)

src/syntax/TreeParser.cpp

@@ -272,7 +272,7 @@ HelpFrame HelpFrame::makeChild()
 {
     flush();
     HelpFrame child = *this; // copy ctor
-    return child; // c++17 spec says NRVO elides the move constructor here, but g++ 7.4 uses move ctor.
+    return child;            // C++ standard says NRVO elides the move constructor here.
 }
 
 class NODISCARD TreeParser::HelpCommon final

src/syntax/Value.cpp

@@ -137,6 +137,23 @@ Vector::Base::const_iterator Vector::end() const
     return m_vector->end();
 }
 
+bool Vector::empty() const
+{
+    return m_vector->empty();
+}
+size_t Vector::size() const
+{
+    return m_vector->size();
+}
+const Value &Vector::at(size_t pos) const
+{
+    return m_vector->at(pos);
+}
+const Value &Vector::operator[](size_t pos) const
+{
+    return at(pos);
+}
+
 Vector getAnyVectorReversed(const Pair *const matched)
 {
     size_t len = 0;

src/syntax/Value.h

@@ -38,11 +38,11 @@ struct NODISCARD Vector final
     NODISCARD Base::const_iterator end() const;
 
 public:
-    NODISCARD bool empty() const { return m_vector->empty(); }
-    NODISCARD size_t size() const { return m_vector->size(); }
+    NODISCARD bool empty() const;
+    NODISCARD size_t size() const;
     // NOTE: at() throws if out of range.
-    const Value &at(size_t pos) const { return m_vector->at(pos); }
-    const Value &operator[](size_t pos) const { return at(pos); }
+    const Value &at(size_t pos) const;
+    const Value &operator[](size_t pos) const;
 
 public:
     friend std::ostream &operator<<(std::ostream &os, const Vector &v);