CMAKE: PNG fails on MinGW-w64

[carlo-bramini]

I tried to build SDL3_image-3.4.0 with MinGW-w64.
When configuring with CMake, this error message is printed on the console:

CMake Error at cmake/PrivateSdlFunctions.cmake:220 (message):
  PNG::PNG is not a shared library, but has type=INTERFACE_LIBRARY
Call Stack (most recent call first):
  CMakeLists.txt:906 (target_get_dynamic_library)

All my cross compilers for x86_64/i686/aarch64 show the same result.
The bug doesn't happen with version 3.2.6.
At the moment, I added the option -DSDLIMAGE_PNG_LIBPNG=OFF to CMake for bypassing the problem
However, I have not understood if this is an expected behaviour and this is the right solution for closing the issue.
I also tried to use libpng-1.6.47 and libpng-1.6.54 but it does not seem to be related to the version of the library.

[slouken]

@madebr, this might be the key to the libpng issue people are reporting?

[madebr]

@madebr, this might be the key to the libpng issue people are reporting?

I see a potential problem with SDLIMAGE_PNG_LIBPNG not being defined in the exported SDL3_imageConfig.cmake (pr incoming).

But the issue here is different: configuring SDL3_image itself is failing here.

How are you providing PNG? Our mechanism to calculate the filename of the dynamic library (e.g. libpng16-16.dll, libpng.so.16) only supports IMPORTED and SHARED targets, not INTERFACE targets.

FindPNG.cmake from CMake provides an IMPORTED one:
https://github.com/Kitware/CMake/blob/a4d9a20c49fbf2a157c577fd6c64a0cdd0e66c36/Modules/FindPNG.cmake#L173-L177

This issue is not new with 3.4: configuring 3.2.x with -DSDLIMAGE_PNG=ON -DSDLIMAGE_PNG_SHARED=ON -DSDLIMAGE_BACKEND_STB=OFF should trigger the same code.

[carlo-bramini]

How are you providing PNG? Our mechanism to calculate the filename of the dynamic library (e.g. libpng16-16.dll, libpng.so.16) only supports IMPORTED and SHARED targets, not INTERFACE targets.

You can find everything about the libpng packages for MinGW-w64 cross compilers from my repository here:

https://github.com/carlo-bramini/packages-cygwin/tree/main/libpng

x86_64 and i686 packages are identical, they just differ for the CPU target.
Packages for aarch64 are not yet released, but they are identical to the above.
And here:

https://github.com/carlo-bramini/packages-cygwin/tree/main/sdl3

there are the packages for SDL3-3.4.0-1.
Perhaps, you will find these sources and the binaries and their build scripts useful.

[madebr]

Thanks for the link to the prebuilt libpng archive. Can you try #685?

[carlo-bramini]

Unfortunately, it did not change.
Here there are your sources:

$ git branch
* PNG_shared-if-available
  main

but I also verified myself that the correction was there and here:

-- The C compiler identification is GNU 14.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/x86_64-w64-mingw32-gcc.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Configuring SDL3_image 3.5.0
-- Detecting Target CPU Architecture
-- Detecting Target CPU Architecture - X64
-- Performing Test LINKER_SUPPORTS_VERSION_SCRIPT
-- Performing Test LINKER_SUPPORTS_VERSION_SCRIPT - Success
-- Performing Test HAVE_WL_NO_UNDEFINED
-- Performing Test HAVE_WL_NO_UNDEFINED - Success
-- SDL3_image: Using system libavif
-- Dynamic libavif: libavif-16.dll
-- Found ZLIB: /usr/x86_64-w64-mingw32/sys-root/mingw/lib/libz.dll.a (found version "1.3.1")
-- SDL3_image: Using system libpng
CMake Error at cmake/PrivateSdlFunctions.cmake:220 (message):
  PNG::PNG is not a shared library, but has type=INTERFACE_LIBRARY
Call Stack (most recent call first):
  CMakeLists.txt:911 (target_get_dynamic_library)


-- Dynamic libpng: $<TARGET_FILE_NAME:PNG::PNG>
-- Found TIFF: /usr/x86_64-w64-mingw32/sys-root/mingw/lib/libtiff.dll.a (found version "4.0.9")
-- SDL3_image: Using system libtiff
-- Dynamic libtiff: libtiff-5.dll
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- SDL3_image: Using system libwebp
-- Dynamic libwebpdemux: libwebpdemux-2.dll
-- Dynamic libwebpmux: libwebpmux-3.dll
-- Dynamic libwebp: libwebp-7.dll
-- SDL3_image backends:
-- - enabled:  stb avif ani bmp gif jpg lbm pcx png apng pnm qoi svg tga tif webp xcf xpm xv
-- - disabled: imageio wic jxl
-- Configuring incomplete, errors occurred!

there is the output generated by CMake.