cmake config: Use find_dependency to make linked targets available

[autoantwort]

When compiled as static lib the generated config contains the following

set_target_properties(avif PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
  INTERFACE_LINK_LIBRARIES "\$<LINK_ONLY:m>;\$<LINK_ONLY:Threads::Threads>"
)

but the target Threads::Threads is not known because the following is missing:

include(CMakeFindDependencyMacro)
set(CMAKE_THREAD_PREFER_PTHREADS ON)
set(THREADS_PREFER_PTHREAD_FLAG ON)
find_dependency(Threads)

like in the CMakeLists.txt

[jzern]

Thanks for the patch. I made a similar fix in libwebp a little while ago.

I extended our tests to include an executable to make sure the dependencies worked. Maybe .github/workflows/ci-unix-static.yml can be extended similarly.

    cat > CMakeLists.txt <<EOF
cmake_minimum_required(VERSION 2.8.12)

project(libwebp C)

find_package(WebP)
if(NOT WebP_FOUND)
  message(FATAL_ERROR "WebP package not found")
endif()
message("WebP_FOUND: \${WebP_FOUND}")
message("WebP_INCLUDE_DIRS: \${WebP_INCLUDE_DIRS}")
message("WebP_LIBRARIES: \${WebP_LIBRARIES}")
message("WEBP_INCLUDE_DIRS: \${WEBP_INCLUDE_DIRS}")
message("WEBP_LIBRARIES: \${WEBP_LIBRARIES}")

if(POLICY CMP0028)
  cmake_policy(SET CMP0028 NEW)
endif()

add_executable(main "main.c")
target_link_libraries(main WebP::webp)
target_include_directories(main PRIVATE ${WEBP_INCLUDE_DIRS})
EOF
cat > main.c << EOF
#include "webp/encode.h"

int main() { return WebPGetEncoderVersion(); }
EOF

[jzern]

I suppose in the shared object case, the library's dependency is enough.

[jzern]

CMAKE_THREAD_PREFER_PTHREAD?

It looks like this flag went away somewhere between 3.2.x and 3.26.x (or it's left out from the documentation)

https://cmake.org/cmake/help/v3.2/module/FindThreads.html
https://cmake.org/cmake/help/latest/module/FindThreads.html

[jzern]

Thanks for the patch. I made a similar fix in libwebp a little while ago.

I extended our tests to include an executable to make sure the dependencies worked. Maybe .github/workflows/ci-unix-static.yml can be extended similarly.

    cat > CMakeLists.txt <<EOF
cmake_minimum_required(VERSION 2.8.12)

project(libwebp C)

find_package(WebP)
if(NOT WebP_FOUND)
  message(FATAL_ERROR "WebP package not found")
endif()
message("WebP_FOUND: \${WebP_FOUND}")
message("WebP_INCLUDE_DIRS: \${WebP_INCLUDE_DIRS}")
message("WebP_LIBRARIES: \${WebP_LIBRARIES}")
message("WEBP_INCLUDE_DIRS: \${WEBP_INCLUDE_DIRS}")
message("WEBP_LIBRARIES: \${WEBP_LIBRARIES}")

if(POLICY CMP0028)
  cmake_policy(SET CMP0028 NEW)
endif()

add_executable(main "main.c")
target_link_libraries(main WebP::webp)
target_include_directories(main PRIVATE ${WEBP_INCLUDE_DIRS})
EOF
cat > main.c << EOF
#include "webp/encode.h"

int main() { return WebPGetEncoderVersion(); }
EOF

I forgot to include the invocation:

cmake . -DCMAKE_PREFIX_PATH="${BUILD_DIR}/webp-install/usr/local"
make

[jzern]

I'm sorry, I lost track of this. There have been changes to the cmake files and this will need to be rebased.

cc: @fdintino