Getting CMake to build shared library for MSVC [du

Question

This question already has an answer here:

• cmake link shared library on Windows 2 answers

I've been building C and C++ projects in unix environments using CMake. However, I want to also start compiling in MSVC and I'm trying to get my head around the cmake documentation but I'm getting stuck. I keep getting the following message when I try to build.

LINK : fatal error LNK1104: cannot open file 'Debug\MyLibrary.lib' [C:\sandbox\projects\cpp\DummyChelloWorld\build\ma inProgram.vcxproj]

Can you tell me what I'm doing wrong?

CMakeLists.txt

    cmake_minimum_required(VERSION 3.4)
    project(helloWorld)

    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
    include(GenerateExportHeader)

    ADD_LIBRARY(MyLibrary SHARED myShared.cpp)

    set(SOURCE_FILES main.cpp)

    GENERATE_EXPORT_HEADER( MyLibrary
                 BASE_NAME MyLibrary
                 EXPORT_MACRO_NAME MyLibrary_EXPORT
                 EXPORT_FILE_NAME ${CMAKE_BINARY_DIR}/MyLibrary_Export.h
                 STATIC_DEFINE MyLibrary_BUILT_AS_STATIC
            )

    add_executable(mainProgram ${SOURCE_FILES})
    TARGET_LINK_LIBRARIES(mainProgram MyLibrary)
    TARGET_INCLUDE_DIRECTORIES(mainProgram PUBLIC exports)

main.cpp

#include "myShared.h"

int main() {
  sayHI();
  return 0;
}

myShared.cpp

#include <iostream>
#include "myShared.h"

using namespace std;

void sayHI() {
  cout << "Hello World lib" << endl;
}

myShared.h

    #ifndef HELLOWORLD_HELLO_H
    #define HELLOWORLD_HELLO_H

    void sayHI();

    #endif //HELLOWORLD_HELLO_H

Answer 1

Turning my comment into an answer

For CMake Version >= 3.4

Just use CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS:

cmake_minimum_required(VERSION 3.4)
project(helloWorld)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS 1)

add_library(MyLibrary SHARED myShared.cpp)

set(SOURCE_FILES main.cpp)
add_executable(mainProgram ${SOURCE_FILES})
TARGET_LINK_LIBRARIES(mainProgram MyLibrary)

For CMake Version < 3.4

You need to declare your functions/symbols as exported. So in your case, you have to modify the following files:

myShared.h

#ifndef HELLOWORLD_HELLO_H
#define HELLOWORLD_HELLO_H

#include "MyLibrary_Export.h"

void MyLibrary_EXPORT sayHI();

#endif //HELLOWORLD_HELLO_H

CMakeLists.txt

cmake_minimum_required(VERSION 3.4)
project(helloWorld)

set(CMAKE_CXX_STANDARD 11)
include(GenerateExportHeader)

add_library(
    MyLibrary 
    SHARED 
        myShared.cpp
        myShared.h
        MyLibrary_Export.h   
)
GENERATE_EXPORT_HEADER( 
    MyLibrary
    BASE_NAME MyLibrary
    EXPORT_MACRO_NAME MyLibrary_EXPORT
    EXPORT_FILE_NAME MyLibrary_Export.h
    STATIC_DEFINE MyLibrary_BUILT_AS_STATIC
)
target_include_directories(MyLibrary PUBLIC "${CMAKE_CURRENT_BINARY_DIR}")

set(SOURCE_FILES main.cpp)
add_executable(mainProgram ${SOURCE_FILES})
TARGET_LINK_LIBRARIES(mainProgram MyLibrary)

I've

1. added MyLibrary_EXPORT to your function declaration
2. added the CMAKE_CURRENT_BINARY_DIR to the shared libraries include paths (to point to the generated export definitions header)
3. made use of the more cross-platform CMAKE_CXX_STANDARD definition.

Alternative

References

• cmake link shared library on Windows
• Export all symbols when creating a DLL