Add: introduce CMake for project management

CMake works on all our supported platforms, like MSVC, Mingw, GCC,
Clang, and many more. It allows for a single way of doing things,
so no longer we need shell scripts and vbs scripts to work on all
our supported platforms.

Additionally, CMake allows to generate project files for like MSVC,
KDevelop, etc.

This heavily reduces the lines of code we need to support multiple
platforms from a project perspective.

Addtiionally, this heavily improves our detection of libraries, etc.

1 files changed, 120 insertions, 0 deletions

diff --git a/cmake/CompileFlags.cmake b/cmake/CompileFlags.cmake
new file mode 100644
index 000000000..05c19abab
--- /dev/null
+++ b/cmake/CompileFlags.cmake
@@ -0,0 +1,120 @@
+# Macro which contains all bits to setup the compile flags correctly.
+#
+# compile_flags()
+#
+macro(compile_flags)
+    if (MSVC)
+        # Switch to MT (static) instead of MD (dynamic) binary
+
+        # For MSVC two generators are available
+        # - a command line generator (Ninja) using CMAKE_BUILD_TYPE to specify the
+        #   configuration of the build tree
+        # - an IDE generator (Visual Studio) using CMAKE_CONFIGURATION_TYPES to
+        #   specify all configurations that will be available in the generated solution
+        list(APPEND MSVC_CONFIGS "${CMAKE_BUILD_TYPE}" "${CMAKE_CONFIGURATION_TYPES}")
+
+        # Set usage of static runtime for all configurations
+        foreach(MSVC_CONFIG ${MSVC_CONFIGS})
+            string(TOUPPER "CMAKE_CXX_FLAGS_${MSVC_CONFIG}" MSVC_FLAGS)
+            string(REPLACE "/MD" "/MT" ${MSVC_FLAGS} "${${MSVC_FLAGS}}")
+        endforeach()
+
+        # "If /Zc:rvalueCast is specified, the compiler follows section 5.4 of the
+        # C++11 standard". We need C++11 for the way we use threads.
+        add_compile_options(/Zc:rvalueCast)
+
+        # Add DPI manifest to project; other WIN32 targets get this via ottdres.rc
+        list(APPEND GENERATED_SOURCE_FILES "${CMAKE_SOURCE_DIR}/os/windows/openttd.manifest")
+    endif (MSVC)
+
+    # Add some -D flags for Debug builds. We cannot use add_definitions(), because
+    # it does not appear to support the $<> tags.
+    add_compile_options(
+        "$<$<CONFIG:Debug>:-D_DEBUG>"
+        "$<$<CONFIG:Debug>:-D_FORTIFY_SOURCE=2>"
+    )
+
+    # Prepare a generator that checks if we are not a debug, and don't have asserts
+    # on. We need this later on to set some compile options for stable releases.
+    set(IS_STABLE_RELEASE "$<AND:$<NOT:$<CONFIG:Debug>>,$<NOT:$<BOOL:${OPTION_USE_ASSERTS}>>>")
+
+    if (MSVC)
+        add_compile_options(/W3)
+    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+        add_compile_options(
+            -W
+            -Wall
+            -Wcast-qual
+            -Wextra
+            -Wsign-compare
+            -Wundef
+            -Wpointer-arith
+            -Wwrite-strings
+            -Wredundant-decls
+            -Wformat-security
+            -Wformat=2
+            -Winit-self
+            -Wnon-virtual-dtor
+
+            # Often parameters are unused, which is fine.
+            -Wno-unused-parameter
+            # We use 'ABCD' multichar for SaveLoad chunks identifiers
+            -Wno-multichar
+
+            # Compilers complains about that we break strict-aliasing.
+            #  On most places we don't see how to fix it, and it doesn't
+            #  break anything. So disable strict-aliasing to make the
+            #  compiler all happy.
+            -fno-strict-aliasing
+        )
+
+        add_compile_options(
+            # When we are a stable release (Release build + USE_ASSERTS not set),
+            # assertations are off, which trigger a lot of warnings. We disable
+            # these warnings for these releases.
+            "$<${IS_STABLE_RELEASE}:-Wno-unused-variable>"
+            "$<${IS_STABLE_RELEASE}:-Wno-unused-but-set-parameter>"
+            "$<${IS_STABLE_RELEASE}:-Wno-unused-but-set-variable>"
+        )
+
+        if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+            include(CheckCXXCompilerFlag)
+            check_cxx_compiler_flag("-flifetime-dse=1" LIFETIME_DSE_FOUND)
+
+            add_compile_options(
+                # GCC 4.2+ automatically assumes that signed overflows do
+                # not occur in signed arithmetics, whereas we are not
+                # sure that they will not happen. It furthermore complains
+                # about its own optimized code in some places.
+                "-fno-strict-overflow"
+
+                # Prevent optimisation supposing enums are in a range specified by the standard
+                # For details, see http://gcc.gnu.org/PR43680
+                "-fno-tree-vrp"
+
+                # -flifetime-dse=2 (default since GCC 6) doesn't play
+                # well with our custom pool item allocator
+                "$<$<BOOL:${LIFETIME_DSE_FOUND}>:-flifetime-dse=1>"
+            )
+        endif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+        add_compile_options(
+            -Wall
+            # warning #873: function ... ::operator new ... has no corresponding operator delete ...
+            -wd873
+            # warning #1292: unknown attribute "fallthrough"
+            -wd1292
+            # warning #1899: multicharacter character literal (potential portability problem)
+            -wd1899
+            # warning #2160: anonymous union qualifier is ignored
+            -wd2160
+        )
+    else ()
+        message(FATAL_ERROR "No warning flags are set for this compiler yet; please consider creating a Pull Request to add support for this compiler.")
+    endif ()
+
+    if (NOT WIN32)
+        # rdynamic is used to get useful stack traces from crash reports.
+        set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -rdynamic")
+    endif (NOT WIN32)
+endmacro()