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Bug 2992

Summary: CMakeLists.txt bugs
Product: SDL Reporter: Yaroslav <saturn4er>
Component: buildAssignee: Ryan C. Gordon <icculus>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: alexander.grund, cseri9, saturn4er, sezeroz
Version: HG 2.1Keywords: target-2.0.14
Hardware: x86_64   
OS: Windows (All)   

Description Yaroslav 2015-05-22 13:43:44 UTC 
I just found bugs in your CMakeLists.txt file in root of sources. When you use target_link_libraries, you should set modificator "LINK_PRIVATE". When I include SDL into my project using add_subdirectory, my main project begin to include same *.lib's file as SDL project. 

Also, line 199 contains «add_definitions(-DUSING_GENERATED_CONFIG_H)». This line causes a error “Wrong SDL_config.h, check your include path?”

This bugs were detected when I generate VS project
Comment 1 cseri 2015-08-03 16:20:18 UTC 
I found the same issue: adding LINK_PRIVATE in CMakeLists was needed to use SDL with add_subdirectory, otherwise VS wanted to link my program with DirectX's lib files which it couldn't find.
(Note: LINK_PRIVATE was introduced in CMake 2.8.7, if you add this fix you should bump the minimum CMake version as well.)

A diff for SDL 2.0.3 is below:

@@ -2,7 +2,7 @@ if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
   message(FATAL_ERROR "Prevented in-tree built. Please create a build directory
 endif()

-cmake_minimum_required(VERSION 2.6)
+cmake_minimum_required(VERSION 2.8.7)
 project(SDL2 C)
 include(CheckFunctionExists)
 include(CheckLibraryExists)
@@ -1254,7 +1254,7 @@ if(SDL_SHARED)
       OUTPUT_NAME "SDL2")
   endif()
  set(_INSTALL_LIBS "SDL2" ${_INSTALL_LIBS})
- target_link_libraries(SDL2 ${EXTRA_LIBS} ${EXTRA_LDFLAGS})
+ target_link_libraries(SDL2 LINK_PRIVATE ${EXTRA_LIBS} ${EXTRA_LDFLAGS})
 endif()

 if(SDL_STATIC)
Comment 2 alexander.grund 2020-02-07 15:17:42 UTC 
Better would be to require CMake 3.x and use PRIVATE instead of LINK_PRIVATE
Comment 3 Ryan C. Gordon 2020-06-27 00:13:08 UTC 
(In reply to alexander.grund from comment #2)
> Better would be to require CMake 3.x and use PRIVATE instead of LINK_PRIVATE

I decided to do that.

https://hg.libsdl.org/SDL/rev/f027f0932dba

I'm resolving this bug, but I don't have an external project to test against, so please reopen if I screwed this up in some way!

--ryan.
Comment 4 Ozkan Sezer 2020-06-27 00:55:55 UTC 
(In reply to alexander.grund from comment #2)
> Better would be to require CMake 3.x and use PRIVATE instead of LINK_PRIVATE

Why is it better?  Does newer cmake versions warn with LINK_PRIVATE
or something?
Comment 5 alexander.grund 2020-06-30 06:40:00 UTC 
See https://cmake.org/cmake/help/latest/command/target_link_libraries.html#libraries-for-a-target-and-or-its-dependents-legacy

> This signature is for compatibility only. Prefer the PUBLIC or PRIVATE keywords instead.

So PRIVATE is the preferred approach and the updated CMake version isn't really an issue as getting a more recent version installed is a no-brainer (build with CMake, install via package, pip, ...)