How Can I Automatically Export All Symbols When Creating a DLL in Visual Studio Using CMake?

Exporting Symbols Automatically in DLL Creation

Introduction

When creating a DLL in Visual Studio 2005, it can be inconvenient to manually export individual symbols or use module definition (.def) files. This article provides a solution to automatically export all symbols without requiring tedious declarations.

Solution: CMake Feature

The latest CMake version (>= 3.3.20150721-g9cd2f) offers a feature that enables automatic symbol exportation. By adding set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON) to the CMakeLists.txt file, the compiler exports all symbols without the need for manual annotations.

Advantages and Limitations

Advantages:

• Significantly simplifies symbol exportation, eliminating the need for __declspec(dllexport) or manual .def file creation.

Limitations:

• Not available in older CMake versions.
• Whole Program Optimization (/GL) is not compatible with automatic symbol exportation.

Detailed Explanation

CMake uses the following approach:

1. During compilation, it generates a "objects.txt" file containing information about the .obj files used in the DLL.
2. It parses the .obj files to extract symbol information.
3. Based on this information, it creates a .def file containing the exported symbols.
4. The DLL is then linked with the .def file to export the symbols automatically.

Usage Example

To use this feature, create a CMake project with the following CMakeLists.txt file:

cmake_minimum_required(VERSION 2.6)
project(myproject)

set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)

set(SOURCE_EXE main.cpp)

include_directories(...)

add_executable(main ${SOURCE_EXE})

target_link_libraries(main ...)

Compile the project, and the DLL will be created with all symbols automatically exported.

Alternative Approaches

There are other methods for exporting symbols, such as:

• Manually Exporting: Adding __declspec(dllexport) to function and class declarations.
• Using Static Libraries and Dumpbin: Dumping symbols from a static library and creating a .def file to export them.
• Using Third-Party Tools: Employing tools like lib or ldd to export symbols.

However, these approaches can be more time-consuming or have limitations compared to the CMake solution.

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