Link error on Apple mobile targets

[Ravbug]

I'm adding an SDL_Image demo to SDL3 Sample. When building for iOS, tvOS and visionOS I get this linker error:

Undefined symbols for architecture arm64:
  "_CGImageSourceCreateImageAtIndex", referenced from:
      _LoadImageFromIOStream in libSDL3_image.a[3](IMG_ImageIO.o)
      _IMG_Load in libSDL3_image.a[3](IMG_ImageIO.o)
  "_CGImageSourceCreateWithDataProvider", referenced from:
      _Internal_isType in libSDL3_image.a[3](IMG_ImageIO.o)
      _LoadImageFromIOStream in libSDL3_image.a[3](IMG_ImageIO.o)
  "_CGImageSourceCreateWithURL", referenced from:
      _IMG_Load in libSDL3_image.a[3](IMG_ImageIO.o)
  "_CGImageSourceGetType", referenced from:
      _Internal_isType in libSDL3_image.a[3](IMG_ImageIO.o)
  "_UTTypeConformsTo", referenced from:
      _Internal_isType in libSDL3_image.a[3](IMG_ImageIO.o)
  "_kCGImageSourceTypeIdentifierHint", referenced from:
      _Internal_isType in libSDL3_image.a[3](IMG_ImageIO.o)
      _LoadImageFromIOStream in libSDL3_image.a[3](IMG_ImageIO.o)
  "_kUTTypeGIF", referenced from:
      _IMG_isGIF in libSDL3_image.a[3](IMG_ImageIO.o)
      _IMG_LoadGIF_IO in libSDL3_image.a[3](IMG_ImageIO.o)
  "_kUTTypeTIFF", referenced from:
      _IMG_isTIF in libSDL3_image.a[3](IMG_ImageIO.o)
      _IMG_LoadTIF_IO in libSDL3_image.a[3](IMG_ImageIO.o)
ld: symbol(s) not found for architecture arm64

I was able to fix it in SDL3 Sample by explicitly linking ImageIO and CoreServices:

if (APPLE)
	find_library(IO_LIB ImageIO)
 	find_library(CS_LIB CoreServices)
	target_link_libraries(${EXECUTABLE_NAME} PUBLIC ${IO_LIB} ${CS_LIB})
endif()

Is it expected for users to link these libraries? Or should SDL_Image be linking them automatically?

[slouken]

This should just be EMSCRIPTEN:
https://github.com/Ravbug/sdl3-sample/blob/edbf595cace68d40023f30e85c4d19a7d4eae1c5/CMakeLists.txt#L14

[madebr]

The error is still valid: using static libraries should still work.

here
You need to put SDL3::SDL3 last.

[slouken]

The error is still valid: using static libraries should still work.

here You need to put SDL3::SDL3 last.

The problem is that if you statically link SDL_image you need to link all the frameworks it uses in the application, which is what @Ravbug's fix is doing. But really we shouldn't be statically linking it.

(You probably also need to put SDL3 last, but that's separate from this issue)

[madebr]

The problem is that if you statically link SDL_image you need to link all the frameworks it uses in the application, which is what @Ravbug's fix is doing. But really we shouldn't be statically linking it.

You're right: SDL3 should be used as a shared library.

But CMake should handle static libraries for us: it propagates these to the final shared library or executable.
This is also why you can use SDL3::SDL3-static in your windows project without having to add the various win32 import libraries.
When we do target_link_options(SDL3_image-static PRIVATE -Wl,-framework,ImageIO), it should appear in the link command of ${EXECUTABLE_NAME}.

[slouken]

Ah, in that case, we probably need to do something like that in the SDL_image CMakeLists.txt for those frameworks. Can you take a look?