Add precompiled header support

Note: the <filesystem> header is not included in the default
precompiled_headers.txt, because we don't use it yet, and it might be big

doc/compiling/README.md

@@ -20,6 +20,8 @@ General options and their default values:
         SemiDebug              - Partially optimized debug build
         RelWithDebInfo         - Release build with debug information
         MinSizeRel             - Release build with -Os passed to compiler to make executable as small as possible
+    PRECOMPILE_HEADERS=FALSE   - Precompile some headers (experimental; requires CMake 3.16 or later)
+    PRECOMPILED_HEADERS_PATH=  - Path to a file listing all headers to precompile (default points to src/precompiled_headers.txt)
     ENABLE_CURL=ON             - Build with cURL; Enables use of online mod repo, public serverlist and remote media fetching via http
     ENABLE_CURSES=ON           - Build with (n)curses; Enables a server side terminal (command line option: --terminal)
     ENABLE_GETTEXT=ON          - Build with Gettext; Allows using translations

src/CMakeLists.txt

@@ -48,6 +48,25 @@ if(NOT (BUILD_CLIENT OR BUILD_SERVER))
 endif()
 
 
+option(PRECOMPILE_HEADERS "Precompile some headers (experimental; requires CMake 3.16 or later)" FALSE)
+set(PRECOMPILED_HEADERS_PATH "" CACHE FILEPATH "Path to a file listing all headers to precompile")
+
+if(PRECOMPILE_HEADERS)
+	if(${CMAKE_VERSION} VERSION_LESS 3.16)
+		message(FATAL_ERROR "PRECOMPILE_HEADERS is on, but precompiled headers require at least CMake 3.16.")
+	endif()
+	if(PRECOMPILED_HEADERS_PATH)
+		set(PRECOMPILED_HEADERS ${PRECOMPILED_HEADERS_PATH})
+	else()
+		set(PRECOMPILED_HEADERS "${CMAKE_SOURCE_DIR}/src/precompiled_headers.txt")
+	endif()
+	message(STATUS "Reading headers to precompile from: ${PRECOMPILED_HEADERS}")
+	# ignore lines that begin with # and empty lines
+	file(STRINGS ${PRECOMPILED_HEADERS} PRECOMPILED_HEADERS_LIST REGEX "^[^#].*$")
+	set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${PRECOMPILED_HEADERS})
+endif()
+
+
 option(ENABLE_CURL "Enable cURL support for fetching media" TRUE)
 set(USE_CURL FALSE)
 
@@ -619,6 +638,10 @@ if(BUILD_CLIENT)
 	if(BUILD_UNITTESTS OR BUILD_BENCHMARKS)
 		target_link_libraries(${PROJECT_NAME} Catch2::Catch2)
 	endif()
+
+	if(PRECOMPILE_HEADERS)
+		target_precompile_headers(${PROJECT_NAME} PRIVATE ${PRECOMPILED_HEADERS_LIST})
+	endif()
 endif(BUILD_CLIENT)
 
 
@@ -682,6 +705,10 @@ if(BUILD_SERVER)
 	if(BUILD_UNITTESTS OR BUILD_BENCHMARKS)
 		target_link_libraries(${PROJECT_NAME}server Catch2::Catch2)
 	endif()
+
+	if(PRECOMPILE_HEADERS)
+		target_precompile_headers(${PROJECT_NAME}server PRIVATE ${PRECOMPILED_HEADERS_LIST})
+	endif()
 endif(BUILD_SERVER)
 
 # See issue #4638

src/precompiled_headers.txt

@@ -0,0 +1,103 @@
+
+# stdlib
+# ------
+
+# C stuff:
+<cassert>
+<cctype>
+<cerrno>
+<cfenv>
+<cfloat>
+<cinttypes>
+<ciso646>
+<climits>
+<clocale>
+<cmath>
+<csetjmp>
+<csignal>
+<cstdarg>
+<cstdbool>
+<cstddef>
+<cstdint>
+<cstdio>
+<cstdlib>
+<cstring>
+<ctgmath>
+<ctime>
+<cuchar>
+<cwchar>
+<cwctype>
+
+# Containers:
+<array>
+<deque>
+<forward_list>
+<list>
+<map>
+<queue>
+<set>
+<stack>
+<unordered_map>
+<unordered_set>
+<vector>
+
+# Input/Output:
+<fstream>
+<iomanip>
+<ios>
+<iosfwd>
+<iostream>
+<istream>
+<ostream>
+<sstream>
+<streambuf>
+
+# Multi-threading:
+<atomic>
+<condition_variable>
+<future>
+<mutex>
+<shared_mutex>
+<thread>
+
+# Other:
+<algorithm>
+<any>
+<bitset>
+<charconv>
+<chrono>
+<codecvt>
+<complex>
+<exception>
+<execution>
+<functional>
+<initializer_list>
+<iterator>
+<limits>
+<locale>
+<memory>
+<memory_resource>
+<new>
+<numeric>
+<optional>
+<random>
+<ratio>
+<regex>
+<stdexcept>
+<string>
+<string_view>
+<system_error>
+<tuple>
+<typeindex>
+<typeinfo>
+<type_traits>
+<utility>
+<valarray>
+<variant>
+
+
+# libs
+# ----
+
+# jsoncpp
+<json/json.h>