Migrate codebase to C++20

- VCMI can now be compiled in C++20 mode
- Replaced all references to C++17 with C++20
- Boost 1.74 is now set as minimal version (older version might work but
untested)
- Updated documentation to reflect required versions of compilers /
libraries
- Removed excessive fail-fast / continue-on-error from CI

.github/workflows/github.yml

@@ -13,7 +13,6 @@ jobs:
   build:
     name: Build (${{ matrix.platform }})
     strategy:
-      fail-fast: false      # Do not cancel whole matrix when one build fails
       matrix:
         include:
           - platform: mac-intel
@@ -126,10 +125,7 @@ jobs:
             artifact_platform: x64
 
     runs-on: ${{ matrix.os }}
-    # Allow non-MSVC builds to fail without failing whole job
+
-    # This keeps pipeline moving so Windows Installer job can still run
-    # MSVC builds must success to continue to Windows Installer job
-    continue-on-error: ${{ !startsWith(matrix.platform, 'msvc') }}
     defaults:
       run:
         shell: bash

CMakeLists.txt

@@ -223,8 +223,9 @@ include(UseDoxygen OPTIONAL)
 #        Compile and linking options       #
 ############################################
 
-#Enable C++17 Globally
+set (CMAKE_CXX_STANDARD 20)
-set (CMAKE_CXX_STANDARD 17)
+set (CMAKE_CXX_STANDARD_REQUIRED ON)
+
 #General visibility options
 set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
@@ -423,18 +424,8 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR NOT WIN32)
 endif()
 
 # Check if some platform-specific libraries are needed for linking
-if(NOT WIN32 AND NOT IOS)
+if(HAIKU)
-	include(CheckLibraryExists)
-
-	# Shared memory functions used by Boost.Interprocess
-	# FindBoost handle linking with pthreads, but doesn't handle this
-	CHECK_LIBRARY_EXISTS(rt shm_open "" HAVE_RT_LIB)
-	if(HAVE_RT_LIB)
-		set(SYSTEM_LIBS ${SYSTEM_LIBS} rt)
-	endif()
-	if(HAIKU)
 	set(SYSTEM_LIBS ${SYSTEM_LIBS} network)
-	endif()
 endif()
 
 if(ENABLE_LUA)
@@ -449,10 +440,10 @@ set(BOOST_COMPONENTS date_time filesystem locale program_options)
 if(ENABLE_INNOEXTRACT)
 	list(APPEND BOOST_COMPONENTS iostreams)
 endif()
-find_package(Boost 1.48.0 REQUIRED COMPONENTS ${BOOST_COMPONENTS})
+find_package(Boost 1.74.0 REQUIRED COMPONENTS ${BOOST_COMPONENTS})
 if(Boost_MAJOR_VERSION EQUAL 1 AND Boost_MINOR_VERSION LESS 69)
 	list(APPEND BOOST_COMPONENTS system)
-	find_package(Boost 1.48.0 REQUIRED COMPONENTS ${BOOST_COMPONENTS})
+	find_package(Boost 1.74.0 REQUIRED COMPONENTS ${BOOST_COMPONENTS})
 endif()
 
 find_package(ZLIB REQUIRED)

client/mapView/MapRendererContext.h

@@ -13,10 +13,7 @@
 
 #include "../lib/GameConstants.h"
 #include "../lib/int3.h"
-
+#include "../lib/spells/ViewSpellInt.h"
-VCMI_LIB_NAMESPACE_BEGIN
-struct ObjectPosInfo;
-VCMI_LIB_NAMESPACE_END
 
 struct MapRendererContextState;
 

client/renderSDL/FontChain.cpp

@@ -115,8 +115,8 @@ size_t FontChain::getGlyphWidthScaled(const char * data) const
 
 std::vector<FontChain::TextChunk> FontChain::splitTextToChunks(const std::string & data) const
 {
-	// U+FFFD - replacement character (question mark in rhombus)
+	// U+FFFD - replacement character (question mark in rhombus, '�')
-	static const std::string replacementCharacter = u8"�";
+	static const std::string replacementCharacter = reinterpret_cast<const char *>(u8"\ufffd");
 
 	std::vector<TextChunk> chunks;
 

client/windows/CQuestLog.h

@@ -9,11 +9,14 @@
  */
 #pragma once
 
+#include "CWindowObject.h"
+
 #include "../widgets/TextControls.h"
 #include "../widgets/MiscWidgets.h"
 #include "../widgets/Images.h"
 #include "../adventureMap/CMinimap.h"
-#include "CWindowObject.h"
+
+#include "../../lib/gameState/QuestInfo.h"
 
 VCMI_LIB_NAMESPACE_BEGIN
 

docs/developers/Building_Linux.md

@@ -1,7 +1,7 @@
 # Building VCMI for Linux
 
-- Current baseline requirement for building is Ubuntu 20.04
+- Current baseline requirement for building is Ubuntu 22.04 or later
-- Supported C++ compilers for UNIX-like systems are GCC 9+ and Clang 13+
+- Supported C++ compilers for UNIX-like systems are GCC 10+ and Clang 13+
 
 Older distributions and compilers might work, but they aren't tested by Github CI (Actions)
 
@@ -15,8 +15,8 @@ To compile, the following packages (and their development counterparts) are need
 - SDL2 with devel packages: mixer, image, ttf
 - minizip or minizip-ng
 - zlib and zlib-devel
-- Boost C++ libraries v1.48+: program-options, filesystem, system, thread, locale
+- Boost C++ libraries: program-options, filesystem, system, thread, locale
-- Recommended, if you want to build launcher or map editor: Qt 5, widget and network modules
+- Recommended, if you want to build launcher or map editor: Qt (widget and network modules)
 - Recommended, FFmpeg libraries, if you want to watch in-game videos: libavformat and libswscale. Their name could be libavformat-devel and libswscale-devel, or ffmpeg-libs-devel or similar names.
 - Optional:
   - if you want to build scripting modules: LuaJIT

docs/developers/Coding_Guidelines.md

@@ -2,9 +2,22 @@
 
 ## C++ Standard
 
-VCMI implementation bases on C++17 standard. Any feature is acceptable as long as it's will pass build on our CI, but there is list below on what is already being used.
+VCMI implementation bases on C++20 standard. Any feature is acceptable as long as it's will pass build on our CI. At the time of writing, following compilers are supported, and any C++20 feature available across all these compilers can be used:
 
-Any compiler supporting C++17 should work, but this has not been thoroughly tested. You can find information about extensions and compiler support at <http://en.cppreference.com/w/cpp/compiler_support>
+- GCC 10 or newer
+- Clang 13 or newer
+- Visual Studio 2022 (MSVC 19.44)
+- XCode 16.2 (Apple Clang 16.0.0)
+
+You can find information about compiler support at <https://en.cppreference.com/w/cpp/compiler_support/20.html>.
+
+Additionally, features that require macOS 10.15 or newer are not available: <https://developer.apple.com/xcode/cpp/#c++20>
+
+- (C++17) Filesystem library
+- (C++17) Elementary string conversions std::to_chars, std::from_chars
+- (C++20) Synchronization library (<barrier>, <latch>, <semaphore> and notification functions on std::atomic)
+- (C++20) Add max() to latch and barrier
+- (C++20) memory_resource
 
 ## Style Guidelines
 

lib/filesystem/CZipLoader.cpp

@@ -241,9 +241,9 @@ bool ZipArchive::extract(const boost::filesystem::path & where, const std::strin
 	{
 #ifdef VCMI_WINDOWS
 		if (fullName.size() < 260)
-			logGlobal->error("Failed to open file '%s'", fullName.c_str());
+			logGlobal->error("Failed to open file '%s'", fullName.string());
 		else
-			logGlobal->error("Failed to open file with long path '%s' (%d characters)", fullName.c_str(), fullName.size());
+			logGlobal->error("Failed to open file with long path '%s' (%d characters)", fullName.string(), fullName.size());
 #else
 		logGlobal->error("Failed to open file '%s'", fullName.c_str());
 #endif

lib/rmg/modificators/WaterProxy.cpp

@@ -28,6 +28,7 @@
 #include "ConnectionsPlacer.h"
 #include "../TileInfo.h"
 #include "WaterAdopter.h"
+#include "WaterRoutes.h"
 #include "../RmgArea.h"
 
 #include <vstd/RNG.h>

lib/rmg/modificators/WaterProxy.h

@@ -13,13 +13,7 @@
 
 VCMI_LIB_NAMESPACE_BEGIN
 
-struct RouteInfo
+struct RouteInfo;
-{
-	rmg::Area blocked;
-	int3 visitable;
-	int3 boarding;
-	rmg::Area water;
-};
 
 class WaterProxy: public Modificator
 {

lib/rmg/modificators/WaterRoutes.h

@@ -13,7 +13,13 @@
 
 VCMI_LIB_NAMESPACE_BEGIN
 
-struct RouteInfo;
+struct RouteInfo
+{
+	rmg::Area blocked;
+	int3 visitable;
+	int3 boarding;
+	rmg::Area water;
+};
 
 class WaterRoutes: public Modificator
 {

lib/spells/Problem.h

@@ -12,6 +12,8 @@
 
 #include <vcmi/spells/Magic.h>
 
+#include "../texts/MetaString.h"
+
 VCMI_LIB_NAMESPACE_BEGIN
 
 namespace spells

lib/spells/adventure/SummonBoatEffect.cpp

@@ -28,7 +28,7 @@ SummonBoatEffect::SummonBoatEffect(const CSpell * s, const JsonNode & config)
 {
 	if (!config["createdBoat"].isNull())
 	{
-		LIBRARY->identifiers()->requestIdentifier("core:boat", config["createdBoat"], [=](int32_t boatTypeID)
+		LIBRARY->identifiers()->requestIdentifier("core:boat", config["createdBoat"], [this](int32_t boatTypeID)
 		{
 			createdBoat = BoatId(boatTypeID);
 		});