cmake: errors when using SDL_sound as submodule

[ccvelandres]

Genexp doesn't work in cmake versions below 3.26 in certain usage. (latest cmake release is still 3.25)

SDL_sound/CMakeLists.txt

Line 248 in 6cb07c2

target_include_directories(SDL2_sound PUBLIC "$<TARGET_PROPERTY:SDL2::SDL2,INTERFACE_INCLUDE_DIRECTORIES>")

See note in https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html#genex:TARGET_PROPERTY for reference.

Directory looks like this:

├── library1
│   ├── CMakeLists.txt              <- library_1 links to SDL_Sound
│   └── SDL_Sound                   <- submodule
├── example
│   └── CMakeLists.txt              <- exe links to library_1 
└── CMakeLists.txt                   <- root CMakeLists

CMake Error at example/CMakeLists.txt:14 (target_link_libraries):
  Error evaluating generator expression:

    $<TARGET_PROPERTY:SDL2::SDL2,INTERFACE_INCLUDE_DIRECTORIES>

  Target "SDL2::SDL2" not found.

[ccvelandres]

53df0ac -- Adds include directories when using SDL_sound as submodule

[sezero]

CC: @madebr

[sezero]

@madebr: Is this good now?

[madebr]

ccvelandres#1 contains my (locally tested) suggestions

[ccvelandres]

Merged ccvelandres#1 and also tested locally on my end

[ccvelandres]

One other thing I've noticed is this: we are disabling RPATH for SDL2_sound which causes this error: cannot open shared object file: No such file or directory during debug build.

In SDL, RPATH depends on ${UNIX_SYS} --> https://github.com/libsdl-org/SDL/blob/SDL2/CMakeLists.txt#L165 and https://github.com/libsdl-org/SDL/blob/SDL2/CMakeLists.txt#L438

Should we enable RPATH for unix systems same as SDL? or enable BUILD_RPATH and skip INSTALL_RPATH?

[madebr]

Should we enable RPATH for unix systems same as SDL? or enable BUILD_RPATH and skip INSTALL_RPATH?

Personally, I would remove these 2 lines.
The cmake scripts of SDL_mixer/SDL_image/SDL_ttf don't care about the runpath.

The default behavior of CMake is imho fine: use a RUNPATH in the build directory, but remove it when installing.

[sezero]

Thanks.