CODEWITHSUNDEEP
cmakejava-native-interfaceshared-libraries
Harper
Harper

Reputation: 1984

Proper way to link static library into shared library with CMake

I have a CMake project with the following structure

root  
 |- common
      |- Bitmap.h
      |- Bitmap.cpp
      |- BytesUtils.h
      |- BytesUtils.cpp
 |- encoding
 |- jni
     |- impl.cpp
 |- main.cpp

The project will create two artifacts: an executable using main.cpp, and a shared library using the source code in jni/ to be loaded by JNI. They both rely on the source files in common and encoding.

Here's my root/CMakeLists.txt

file(GLOB_RECURSE COMMON_SOURCE
    "common/*.h"
    "common/*.cpp"
    )
file(GLOB_RECURSE ENCODING_SOURCE
    "encoding/*.h"
    "encoding/*.cpp"
    )

add_library(common STATIC ${COMMON_SOURCE})
add_library(encoding STATIC ${ENCODING_SOURCE})

add_executable(main main.cpp)
target_link_libraries(main common)
target_link_libraries(main encoding)

add_subdirectory(jni)

and here's the jni/CMakeLists.txt

set(JAVA_HOME "/usr/lib/jvm/jdk1.8.0_221")
#set(JAVA_HOME "/usr/lib/jvm/java-8-openjdk-amd64/")

include_directories(${JAVA_HOME}/include)
include_directories(${JAVA_HOME}/include/linux)

file(GLOB_RECURSE JNI_SOURCE
    "*.h"
    "*.cpp"
    )

add_library(lqf SHARED ${JNI_SOURCE})
target_link_libraries(lqf common)
target_link_libraries(lqf encoding)

When I load the library using JNI I got the following error:

/usr/lib/jvm/jdk1.8.0_221/bin/java: symbol lookup error: /home/harper/git/lqf/lqf-cpp/cmake-build-debug/lib/liblqf.so: undefined symbol: _ZN6common6BitmapC1EPmj

Using nm to look at the generated so, I discovered that all functions from common/Bitmap.cpp are marked as undefined symbol

 U _ZN6common6Bitmap10appendBitsEhj
 U _ZN6common6Bitmap11moveForwardEj
 U _ZN6common6BitmapC1EPmj

But functions from other source code under common/ are included properly

0000000000002894 T _ZN6common10BytesUtils19readIntLittleEndianEPhPj
00000000000028d0 T _ZN6common10BytesUtils35readIntLittleEndianPaddedOnBitWidthEPhPjh
00000000000029d3 T _ZN6common10BytesUtils18readUnsignedVarIntEPhPj

The only difference I can see is that Bitmap is a class and BytesUtils is a collection of functions.

Bitmap.h 

#include <cstdint>

namespace common {
    class Bitmap {
    public:
        Bitmap(uint64_t *data, uint32_t offset);
        void appendWord(uint64_t *word, uint32_t count);
        void appendBits(uint8_t bit, uint32_t rep);
        void moveForward(uint32_t count);
    };
}

Bitmap.cpp:

#include "Bitmap.h"

common::Bitmap::Bitmap(uint64_t *data, uint32_t offset) {...}
void common::Bitmap::appendBits(uint8_t bit, uint32_t repetition) {...}
void common::Bitmap::appendWord(uint64_t *word, uint32_t count) {...}
void common::Bitmap::moveForward(uint32_t count) {...}

So what is a proper way to build the shared library so these symbols are included?

Update @ Sep 24, 2019 21:32

This is caused by dependencies between static libraries. The encoding lib uses common lib but I failed to add the target_link_libraries between them. After adding target_link_libraries(encoding, common) the symbol tables is fixed.

Upvotes: 0

Views: 1043

Answers (1)

Harper
Harper

Reputation: 1984

This is caused by dependencies between static libraries. The encoding lib uses common lib but I failed to add the target_link_libraries between them. After adding target_link_libraries(encoding common) the symbol tables is fixed.

Upvotes: 1

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