Clarify MSVC-only bundled SDL support

BUILDING.md

@@ -12,6 +12,7 @@ Requirements:
 - CMake 3.21+
 
 The repository already contains the required prebuilt Windows SDL packages in `Libraries/`.
+Those bundled packages are intended for **MSVC / Visual Studio**, not MinGW.
 
 Configure and build:
 
@@ -38,6 +39,14 @@ cmake --build build
 ### 3. Legacy Visual Studio solution
 The existing `.sln` and `.vcxproj` files are still in the repo and can still be opened directly in Visual Studio.
 
+### CLion with MinGW on Windows
+This is a different toolchain from MSVC. The bundled SDL packages in `Libraries/` are the Visual C++ SDL package, so they should not be used with MinGW.
+
+Use one of these options instead:
+
+- switch CLion to a Visual Studio toolchain
+- or install MinGW-compatible SDL packages and configure CMake with `-DMOTHERLOAD_USE_BUNDLED_WINDOWS_SDL=OFF`
+
 ## Build output
 
 The CMake build writes the executable to:
@@ -55,6 +64,8 @@ CMake uses the bundled SDL package config files from:
 - `Libraries/SDLMixer/.../cmake`
 - `Libraries/SDLTtf/.../cmake`
 
+These are only used for **MSVC** builds.
+
 ### Linux
 CMake falls back to `pkg-config` and expects these packages to be installed:
 - `sdl2`
@@ -76,6 +87,14 @@ sudo apt install libgl1-mesa-dev
 ### CMake cannot find SDL packages on Linux
 Install the SDL development packages listed above.
 
+### CLion / MinGW on Windows fails while linking SDL2main
+That usually means the Visual Studio SDL package from `Libraries/` is being used with MinGW.
+
+Use one of these fixes:
+
+- use a Visual Studio toolchain in CLion
+- or configure CMake with `-DMOTHERLOAD_USE_BUNDLED_WINDOWS_SDL=OFF` and provide MinGW-compatible SDL libraries
+
 ### The game starts but cannot find assets
 Run the executable from the build output directory, not from the source directory root. The post-build step copies `Resources/` next to the executable.
 

CMakeLists.txt

@@ -7,10 +7,18 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
 
-option(MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL "Use the bundled prebuilt SDL packages on Windows" ON)
+option(MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL "Use the bundled prebuilt SDL packages for MSVC builds on Windows" ON)
 option(MOTHERLOAD_ENABLE_WARNINGS "Enable compiler warnings" ON)
 
-if(WIN32 AND MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL)
+if(WIN32 AND MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL AND NOT MSVC)
+    message(FATAL_ERROR
+        "MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL=ON only supports MSVC/Visual Studio builds. "
+        "The bundled SDL package in Libraries/ is the SDL2 Visual C++ build, not a MinGW build. "
+        "For CLion/MinGW, disable MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL and use MinGW-compatible SDL packages instead."
+    )
+endif()
+
+if(MSVC AND MOTHERLOAD_USE_BUNDLED_WINDOWS_SDL)
     list(PREPEND CMAKE_PREFIX_PATH
         "${CMAKE_SOURCE_DIR}/Libraries/SDLMain/SDL2-2.26.3/cmake"
         "${CMAKE_SOURCE_DIR}/Libraries/SDLImage/SDL2_image-2.6.3/cmake"
@@ -134,6 +142,11 @@ target_include_directories(Motherload
         "${CMAKE_SOURCE_DIR}/Game"
         "${CMAKE_SOURCE_DIR}/Engine"
 )
+
+if(TARGET SDL2::SDL2main)
+    target_link_libraries(Motherload PRIVATE SDL2::SDL2main)
+endif()
+
 target_link_libraries(Motherload
     PRIVATE
         Engine
@@ -143,10 +156,6 @@ target_link_libraries(Motherload
         SDL2_mixer::SDL2_mixer
         SDL2_ttf::SDL2_ttf
 )
-
-if(TARGET SDL2::SDL2main)
-    target_link_libraries(Motherload PRIVATE SDL2::SDL2main)
-endif()
 motherload_enable_warnings(Motherload)
 
 source_group(TREE "${CMAKE_SOURCE_DIR}" FILES ${ENGINE_SOURCES} ${GAME_SOURCES})

README.md

@@ -88,7 +88,9 @@ For the longer version, troubleshooting, and platform notes, see [`BUILDING.md`]
 * Visual Studio 2022 with the Desktop development with C++ workload
 * CMake 3.21 or newer
 
-The repository already contains prebuilt SDL2 / SDL2_image / SDL2_mixer / SDL2_ttf Windows packages in `Libraries/`, and the CMake build will use those by default.
+The repository already contains prebuilt SDL2 / SDL2_image / SDL2_mixer / SDL2_ttf Windows packages in `Libraries/`, and the CMake build will use those by default for **MSVC / Visual Studio** builds.
+
+If you use **CLion with MinGW**, do **not** use the bundled SDL package. It is the Visual C++ SDL build and is not a proper MinGW dependency set.
 
 #### Linux
 Install the development packages first.
@@ -125,6 +127,7 @@ After building, run the generated executable from the build output directory so
 * The original `.sln` and `.vcxproj` files are still present and can still be used in Visual Studio.
 * The CMake build creates the same two logical targets as the solution: `Engine` and `Motherload`.
 * On non-Windows platforms, SDL dependencies are expected to come from the system package manager.
+* On Windows, the bundled SDL dependencies are intended for **MSVC**, not MinGW.
 
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