Undefined SDL2 symbols in 1.20.2

[KBentley57]

When I try to build the latest release, with

option(WITH_EXAMPLES "Build examples" ON)
option(WITH_EXAMPLE_HEIF_VIEW "Build heif-view tool" ON)

I get a lot of undefined symbols related to SDL2. If SDL 2 is found in config mode, it should have targets that can be linked to instead. Changing the examples/CMakeLists.txt from

    find_package(SDL2 NO_MODULE)

    if (SDL2_FOUND)
        add_executable(heif-view ${getopt_sources}
                heif_view.cc
                sdl.cc
                sdl.hh
                common.cc
                common.h)
        target_link_libraries(heif-view PRIVATE heif ${SDL2_LIBRARIES})
        target_include_directories(heif-view PRIVATE ${libheif_SOURCE_DIR} ${SDL2_INCLUDE_DIRS})
        install(TARGETS heif-view RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
    endif ()
endif ()

to

if (WITH_EXAMPLE_HEIF_VIEW)
    find_package(SDL2 NO_MODULE)

    if (SDL2_FOUND)
        add_executable(heif-view ${getopt_sources}
                heif_view.cc
                sdl.cc
                sdl.hh
                common.cc
                common.h)
        target_link_libraries(heif-view PRIVATE heif SDL2::SDL2 SDL2::SDL2main)
        target_include_directories(heif-view PRIVATE ${libheif_SOURCE_DIR} ${SDL2_INCLUDE_DIRS})
        install(TARGETS heif-view RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
    endif ()
endif ()

Allowed everything to compile properly.

[bradh]

Can you say what environment you are trying to compile on (e.g. which Linux distro or Windows variant), which SDL you have, and what the value of SDL2_LIBRARIES is on that environment and library version?

[kmilos]

Must be environment specific, as I had no problems building on MSYS2 w/ SDL2 (not using sdl2-compat mind you)...

As a side note, if one does target_link_libraries() using real targets instead of variables, there is no longer a need for target_include_directories() as the linked target carries that information already.

Edit: even sdl2-compat seems to define SDL2_LIBRARIES...

[farindk]

Let's try to switch to the target syntax and see whether it breaks anywhere...

[KBentley57]

I left out my system details, sorry about that. I doubt it matters much really, but for completeness sake I'm running redhat. The SDL version is 2.0.12. I believe there was another change I had to make in the examples - If you link against SDL::SDL and SDL::SDLMain it seems that you'll also need to change the includes from SDL.h to SDL2/SDL.h. Not a huge change, but something to be aware of. as @kmilos mentioned earlier, this actually simplifies the CMake by removing the need to have ${SDL2_INCLUDE_DIRS} in the target include directories. This same 'bug' is in libde265 as well, which is where I presume this code was pulled from.

Thanks,

Kyle B

cmake --version
cmake version 3.26.5

NAME="Red Hat Enterprise Linux"
VERSION="8.10 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.10"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.10 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8::baseos"
HOME_URL="https://www.redhat.com/"
DOCUMENTATION_URL="https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8"
BUG_REPORT_URL="https://issues.redhat.com/"

[farindk]

Thanks. Yes, I'm aware that it's the same configuration in libde265. I just wanted to wait whether anyone has build problems with the new syntax, and then copying it over to there.

For me on Ubuntu 24.04, both SDL.h and SDL2/SDL.h work. But I understand that including the directory name helps to differentiate SDL1 from SDL2.

[kmilos]

The SDL version is 2.0.12.

That's quite old, seems the compatibility variables were added in 2.23.1...

@farindk The stickler in me noticed SDL2 devs put SDL2::SDL2main first in the list.

[farindk]

@kmilos Thanks. That should then be safe. Let's just wait a week to let this settle and then I'll copy it over to libde265.