godot-cpp/cmake/common_compiler_flags.cmake

#[=======================================================================[.rst:
Common Compiler Flags
---------------------

This file contains host platform toolchain and target platform agnostic
configuration. It includes flags like optimization levels, warnings, and
features. For target platform specific flags look to each of the
``cmake/<platform>.cmake`` files.

The default compile and link options CMake adds can be found in the
platform modules_. When a project is created it initializes its variables from
the ``CMAKE_*`` values. The cleanest way I have found to alter these defaults
is the use of the ``CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE`` as demonstrated by
the emsdkHack.cmake to overcome the limitation on shared library creation.

So far the emsdkHack is the only modification to the defaults we have made.

.. _modules: https://github.com/Kitware/CMake/blob/master/Modules/Platform/

]=======================================================================]

#[[ Compiler Configuration, not to be confused with build targets ]]
set( DEBUG_SYMBOLS "$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>" )

#[[ Compiler Identification ]]
set( IS_CLANG "$<CXX_COMPILER_ID:Clang>" )
set( IS_APPLECLANG "$<CXX_COMPILER_ID:AppleClang>" )
set( IS_GNU "$<CXX_COMPILER_ID:GNU>" )
set( IS_MSVC "$<CXX_COMPILER_ID:MSVC>" )
set( NOT_MSVC "$<NOT:$<CXX_COMPILER_ID:MSVC>>" )

set( LT_V8  "$<VERSION_LESS:$<CXX_COMPILER_VERSION>,8>" )
set( GE_V9  "$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,9>" )
set( GT_V11 "$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,11>" )
set( LT_V11 "$<VERSION_LESS:$<CXX_COMPILER_VERSION>,11>" )
set( GE_V12 "$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,12>" )

#[===========================[ compiler_detection ]===========================]
#[[ Check for clang-cl with MSVC frontend
The compiler is tested and set when the project command is called.
The variable CXX_COMPILER_FRONTEND_VARIANT was introduced in 3.14
The generator expression $<CXX_COMPILER_FRONTEND_VARIANT> wasn't introduced
until CMake 3.30 so we can't use it yet.

So to support clang downloaded from llvm.org which uses the MSVC frontend
by default, we need to test for it. ]]
function( compiler_detection )
    if( ${CMAKE_CXX_COMPILER_ID} STREQUAL Clang )
        if( ${CMAKE_CXX_COMPILER_FRONTEND_VARIANT} STREQUAL MSVC )
            message( "Using clang-cl" )
            set( IS_CLANG   "0" PARENT_SCOPE )
            set( IS_MSVC    "1" PARENT_SCOPE )
            set( NOT_MSVC   "0" PARENT_SCOPE )
        endif ()
    endif ()
endfunction(  )

#[=========================[ common_compiler_flags ]=========================]
#[[ This function assumes it is being called from within one of the platform
generate functions, with all the variables from lower scopes defined. ]]
function( common_compiler_flags )

    # These compiler options reflect what is in godot/SConstruct.
    target_compile_options( ${TARGET_NAME}
        # The public flag tells CMake that the following options are transient,
        #and will propagate to consumers.
        PUBLIC
            # Disable exception handling. Godot doesn't use exceptions anywhere, and this
            # saves around 20% of binary size and very significant build time.
            $<${DISABLE_EXCEPTIONS}:$<${NOT_MSVC}:-fno-exceptions>>

            # Enabling Debug Symbols
            $<${DEBUG_SYMBOLS}:
                # Adding dwarf-4 explicitly makes stacktraces work with clang builds,
                # otherwise addr2line doesn't understand them.
                $<${NOT_MSVC}:
                    -gdwarf-4
                    $<IF:${IS_DEV_BUILD},-g3,-g2>
                >
            >

            $<${IS_DEV_BUILD}:$<${NOT_MSVC}:-fno-omit-frame-pointer -O0>>

            $<${HOT_RELOAD}:$<${IS_GNU}:-fno-gnu-unique>>

        # Warnings below, these do not need to propagate to consumers.
        PRIVATE

        # MSVC only
        $<${IS_MSVC}:
            # /MP isn't valid for clang-cl with msvc frontend
            $<$<CXX_COMPILER_ID:MSVC>:/MP${PROC_N}>

            /W4      # Warning level 4 (informational) warnings that aren't off by default.
            # Disable warnings which we don't plan to fix.
            /wd4100  # C4100 (unreferenced formal parameter): Doesn't play nice with polymorphism.
            /wd4127  # C4127 (conditional expression is constant)
            /wd4201  # C4201 (non-standard nameless struct/union): Only relevant for C89.
            /wd4244  # C4244 C4245 C4267 (narrowing conversions): Unavoidable at this scale.
            /wd4245
            /wd4267
            /wd4305  # C4305 (truncation): double to float or real_t, too hard to avoid.
            /wd4514  # C4514 (unreferenced inline function has been removed)
            /wd4714  # C4714 (function marked as __forceinline not inlined)
            /wd4820  # C4820 (padding added after construct)

            /utf-8
        >

        # Clang and GNU common options
        $<$<OR:${IS_CLANG},${IS_GNU}>:
            -Wall
            -Wctor-dtor-privacy
            -Wextra
            -Wno-unused-parameter
            -Wnon-virtual-dtor
            -Wwrite-strings
        >

        # Clang only
        $<${IS_CLANG}:
            -Wimplicit-fallthrough
            -Wno-ordered-compare-function-pointers
        >

        # GNU only
        $<${IS_GNU}:
            -Walloc-zero
            -Wduplicated-branches
            -Wduplicated-cond
            -Wno-misleading-indentation
            -Wplacement-new=1
            -Wshadow-local
            -Wstringop-overflow=4
        >

        # Bogus warning fixed in 8+.
        $<${IS_GNU}:$<${LT_V8}:-Wno-strict-overflow>>

        $<${IS_GNU}:$<${GE_V9}:-Wattribute-alias=2>>

        # Broke on MethodBind templates before GCC 11.
        $<${IS_GNU}:$<${GT_V11}:-Wlogical-op>>

        # Regression in GCC 9/10, spams so much in our variadic templates that we need to outright disable it.
        $<${IS_GNU}:$<${LT_V11}:-Wno-type-limits>>

        # False positives in our error macros, see GH-58747.
        $<${IS_GNU}:$<${GE_V12}:-Wno-return-type>>

    )

    target_compile_definitions(${TARGET_NAME}
        PUBLIC
            GDEXTENSION

            # features
            $<${DEBUG_FEATURES}:DEBUG_ENABLED DEBUG_METHODS_ENABLED>

            $<${IS_DEV_BUILD}:DEV_ENABLED>

            $<${HOT_RELOAD}:HOT_RELOAD_ENABLED>

            $<$<STREQUAL:${GODOT_PRECISION},double>:REAL_T_IS_DOUBLE>

            $<${IS_MSVC}:$<${DISABLE_EXCEPTIONS}:_HAS_EXCEPTIONS=0>>
    )

    target_link_options( ${TARGET_NAME}
        PRIVATE
            $<${IS_MSVC}:/WX /MANIFEST:NO>
            # /WX             # treat link warnings as errors.
            # /MANIFEST:NO    # We dont need a manifest

            $<$<NOT:${DEBUG_SYMBOLS}>:
                $<${IS_GNU}:-s>
                $<${IS_CLANG}:-s>
                $<${IS_APPLECLANG}:-Wl,-S -Wl,-x -Wl,-dead_strip>
            >
    )

endfunction()