使用 cmake 为 android 构建 libpng 失败

Question

I am trying to build libpng 1.6.34 to use on my android project. I also try to use cmake

this is build_libpng.sh file

export CMAKE_SYSTEM_NAME=Android
export CMAKE_BUILD_TYPE=Debug
export CMAKE_TOOLCHAIN_FILE=~/android-sdk/ndk-bundle/build/cmake/android.toolchain.cmake
export CMAKE_LIBRARY_OUTPUT_DIRECTORY=obj/armeabi-v7a 

export ANDROID_ABI=armeabi-v7a
export ANDROID_PLATFORM=android-15
export ANDROID_NDK=~/android-sdk/ndk-bundle
export CMAKE_CXX_FLAGS=-frtti -fexceptions

export ZLIB_INCLUDE_DIR=./zlib.1.2.11 
export ZLIB_LIBRARY=./zlib.1.2.11 

~/android-sdk/cmake/3.6.4111459/bin/cmake  -G"Android Gradle - Unix Makefiles"  ./lpng1634/CMakeLists.txt

after execute build_libpng.sh and call make this is the log.

Scanning dependencies of target genfiles
[  0%] Built target genfiles
Scanning dependencies of target png
[  2%] Building C object CMakeFiles/png.dir/png.c.o
[  5%] Building C object CMakeFiles/png.dir/pngerror.c.o
[  8%] Building C object CMakeFiles/png.dir/pngget.c.o
[ 11%] Building C object CMakeFiles/png.dir/pngmem.c.o
[ 13%] Building C object CMakeFiles/png.dir/pngpread.c.o
[ 16%] Building C object CMakeFiles/png.dir/pngread.c.o
[ 19%] Building C object CMakeFiles/png.dir/pngrio.c.o
[ 22%] Building C object CMakeFiles/png.dir/pngrtran.c.o
[ 25%] Building C object CMakeFiles/png.dir/pngrutil.c.o
[ 27%] Building C object CMakeFiles/png.dir/pngset.c.o
[ 30%] Building C object CMakeFiles/png.dir/pngtrans.c.o
[ 33%] Building C object CMakeFiles/png.dir/pngwio.c.o
[ 36%] Building C object CMakeFiles/png.dir/pngwrite.c.o
[ 38%] Building C object CMakeFiles/png.dir/pngwtran.c.o
[ 41%] Building C object CMakeFiles/png.dir/pngwutil.c.o
[ 44%] Linking C shared library obj/armeabi-v7a/libpng16d.so
[]/android-sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: error: cannot open [...]/third_party/lpng1634/libpng.vers: No such file or directory
[...]/android-sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: fatal error: unable to parse version script file [...]/third_party/lpng1634/libpng.vers
clang: error: linker command failed with exit code 1 (use -v to see invocation)
CMakeFiles/png.dir/build.make:459: recipe for target 'obj/armeabi-v7a/libpng16d.so' failed
make[2]: *** [obj/armeabi-v7a/libpng16d.so] Error 1
CMakeFiles/Makefile2:99: recipe for target 'CMakeFiles/png.dir/all' failed
make[1]: *** [CMakeFiles/png.dir/all] Error 2
Makefile:127: recipe for target 'all' failed
make: *** [all] Error 2

I read the lpng1634/CMakeLists.txt has some I dont realy understand.

At this part

if(NOT AWK OR ANDROID)
  # No awk available to generate sources; use pre-built pnglibconf.h
  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf.h.prebuilt
                 ${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h)
  add_custom_target(genfiles) # Dummy

else()
... code for generating libpng.vers here
endif(NOT AWK OR ANDROID)

but this part

if(PNG_SHARED)
  add_library(png SHARED ${libpng_sources})
  set(PNG_LIB_TARGETS png)
  set_target_properties(png PROPERTIES OUTPUT_NAME ${PNG_LIB_NAME})
  add_dependencies(png genfiles)
  if(MSVC)
    # msvc does not append 'lib' - do it here to have consistent name
    set_target_properties(png PROPERTIES PREFIX "lib")
    set_target_properties(png PROPERTIES IMPORT_PREFIX "lib")
  endif()
  target_link_libraries(png ${ZLIB_LIBRARY} ${M_LIBRARY})

  if(UNIX AND AWK)
      if(HAVE_LD_VERSION_SCRIPT)
        set_target_properties(png PROPERTIES LINK_FLAGS
          "-Wl,--version-script='${CMAKE_CURRENT_BINARY_DIR}/libpng.vers'")
      elseif(HAVE_SOLARIS_LD_VERSION_SCRIPT)
        set_target_properties(png PROPERTIES LINK_FLAGS
          "-Wl,-M -Wl,'${CMAKE_CURRENT_BINARY_DIR}/libpng.vers'")
      endif()
  endif()
endif()

using libpng.vers that is the cause of my problem i guess.

Did I config something wrong? can you help?

Answer 1

TLDR

Use the -DHAVE_LD_VERSION_SCRIPT=OFF option, disable building the shared library -DPNG_SHARED=OFF or dig deep into the cmake code upstream

cmake -DHAVE_LD_VERSION_SCRIPT=OFF ./lpng1634

Slightly longer version

... just as far as I followed up on it ...

When building a .so file, libpng wants to version it. For this it pregenerates a number of files, among them libpng.vers . If ANDROID is defined (or AWK is not available) it skips generating the libpng.vers file. Even if it was not generated, it will still tell the linker to use it and fails (leading to the error you posted). You can trick cmake into skipping the versioning by specifying -DHAVE_LD_VERSION_SCRIPT=OFF .

One might ask now why it does not just generate this .vers file, so everything works. It looks like the generator uses a handcrafted compiler invocation which is not super solid and fails when cross compiling for some architectures. The right choice would likely be digging into these scripts and fixing things up there.