CMake Lib in Linux Docker missing dependencies

I use CMake to create the DLL and SO file from my own C++ library, which I then call in my C# code via DLLImport. This has worked so far under Windows and under Linux (Docker). Now the library has been extended, which continues to work on Windows with the DLL. However, under Linux I now get the following error message when calling a DLL function:

Unable to load shared library ‘CustomLib’ or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: libCustomLib: cannot open shared object file: No such file or directory

Since it worked before under Linux I think it should find the library and therefore the dependencies are the problem. But now I don’t know how to proceed.

A colleague helped me with the analysis and I got the following information

root@f266455d4988:/app# LD_DEBUG=all /app/libCustomLib.so
Segmentation fault

root@f266455d4988:/app# ldd ./libCustomLib.so
        linux-vdso.so.1 (0x00007ffc9d983000)
        libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f05720a5000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f057208b000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0571eca000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f0571d47000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f05722d8000)
root@f266455d4988:/app#

I’m using .NET 5.0 and the GCC-compiler

CMake-configuration

      "name": "Linux-GCC-Debug",
      "generator": "Ninja",
      "configurationType": "Debug",
      "cmakeExecutable": "cmake",
      "remoteCopySourcesExclusionList": [ ".vs", ".git", "out" ],
      "cmakeCommandArgs": "",
      "buildCommandArgs": "",
      "ctestCommandArgs": "",
      "inheritEnvironments": [ "linux_x64" ],
      "remoteMachineName": "${defaultRemoteMachineName}",
      "remoteCMakeListsRoot": "$HOME/.vs/${projectDirName}/${workspaceHash}/src",
      "remoteBuildRoot": "$HOME/${projectDirName}/${name}",
      "remoteInstallRoot": "$HOME/.vs/${projectDirName}/${workspaceHash}/out/install/${name}",
      "remoteCopySources": true,
      "rsyncCommandArgs": "-t --delete --delete-excluded",
      "remoteCopyBuildOutput": false,
      "remoteCopySourcesMethod": "rsync",
      "addressSanitizerRuntimeFlags": "detect_leaks=0"

CMakeLists.txt

cmake_minimum_required (VERSION 3.8)

include_directories(${CMAKE_SOURCE_DIR}/CustomLib/xyz)
include_directories(${CMAKE_SOURCE_DIR}/CustomLib/xxx)
link_directories(${CMAKE_LIBRARY_OUTPUT_DIRECTORY})

file(GLOB headers *.h)
file(GLOB headers *.hpp)

add_library (CustomLib SHARED CustomLib.cpp 
                ...
                ${headers})

add_executable (CustomLibExe CustomLib.cpp                
                ${headers})

target_compile_features(CustomLib PUBLIC cxx_std_17)
target_compile_features(CustomLibExe PUBLIC cxx_std_17)

target_compile_options (CustomLib PUBLIC -fexceptions)
target_compile_options (CustomLibExe PUBLIC -fexceptions)

Dockerfile

FROM mcr.microsoft.com/dotnet/aspnet:5.0 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:5.0 AS build
WORKDIR /src
COPY ["testAPI/testAPI.csproj", "testAPI/"]
RUN dotnet restore "testAPI/testAPI.csproj"
COPY . .
WORKDIR "/src/testAPI"
RUN dotnet build "testAPI.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "testAPI.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "testAPI.dll"]

api-part of docker-compose

test_api:
    image: ${DOCKER_REGISTRY-}testapi
    container_name: testapi
    build:
      context: .
      dockerfile: testAPI/Dockerfile

    networks:
      - test_network

    depends_on:
     - test_sql

    environment:
     LD_LIBRARY_PATH: "/app"
     #LD_LIBRARY_PATH: "/lib/x86_64-linux-gnu"

    ports:
     - "5000:80"

Answer

We have solved the problem. The reason was that the backend was running a different Linux distribution (Debian) than the Linux in which the DLL/SO was built (Ubuntu).

I changed the image in the dockerfile from …:5.0 to …:5.0-focal for Ubuntu.

FROM mcr.microsoft.com/dotnet/aspnet:5.0-focal AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:5.0-focal AS build
WORKDIR /src

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Answer