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Oct 13, 2025 by talynt.org 21 views

Introduction

When working with the Microsoft Visual Studio (MSVC) environment, developers often encounter issues with configuring the runtime library settings. One such issue is the inability to select the MultiThreaded or MultiThreadedDLL options in the project settings. This problem can be particularly frustrating when trying to optimize the performance of multi-threaded applications. In this article, we will delve into the root cause of this issue and explore possible solutions to resolve it.

Description

The problem arises when using the CMake build system, specifically in the CMakeLists.txt file. When the BUILD_SHARED_LIBS option is set to FALSE (or OFF), the runtime library is forcibly set to MultiThreaded. This behavior is hardcoded and does not allow for flexibility in configuring the build options. Instead of relying on this hardcoded behavior, it would be more beneficial to utilize the CMAKE_MSVC_RUNTIME_LIBRARY option to make MultiThreaded and MultiThreadedDLL configurable build options.

Example/How to Reproduce

To reproduce this issue, follow these steps:

Create a cpr::Session: Start by creating a cpr::Session object, which is a crucial component in the CMake build system.
Set option ...: Set the BUILD_SHARED_LIBS option to FALSE (or OFF) in the CMakeLists.txt file.
Perform the request: Perform the request to build the project, and observe the error message.
See error: The error message will indicate that the runtime library is forcibly set to MultiThreaded, and the MultiThreadedDLL option is not available.

Possible Fix

Unfortunately, there is no straightforward solution to this issue. However, we can explore alternative approaches to resolve the problem.

Alternative Approach 1: Use the CMAKE_MSVC_RUNTIME_LIBRARY Option

One possible solution is to use the CMAKE_MSVC_RUNTIME_LIBRARY option to configure the runtime library settings. This option allows you to specify the runtime library to use, including MultiThreaded and MultiThreadedDLL.

To use this option, add the following line to your CMakeLists.txt file:

set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded")

Alternatively, you can use the CMAKE_MSVC_RUNTIME_LIBRARY option to specify the MultiThreadedDLL option:

set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")

Alternative Approach 2: Modify the CMakeLists.txt File

Another possible solution is to modify the CMakeLists.txt file to remove the hardcoded behavior. You can do this by adding the following lines to the file:

if(BUILD_SHARED_LIBS)
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")
else()
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded")
endif()

This will allow you to configure the runtime library settings based on the value of the BUILD_SHARED_LIBS option.

Conclusion

In conclusion, the inability to select MultiThreaded or MultiThreadedDLL in the MSVC environment is a common issue that can be resolved by using alternative approaches. By utilizing the CMAKE_MSVC_RUNTIME_LIBRARY option or modifying the CMakeLists.txt file, you can configure the runtime library settings to optimize the performance of your multi-threaded applications.

Additional Context/Your Environment

OS: Windows 10
Version: MSVC 2019
CMake Version: 3.20.0
CMakeLists.txt:

cmake_minimum_required(VERSION 3.20.0)
project(MyProject)

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

if(BUILD_SHARED_LIBS)
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")
else()
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded")
endif()

add_executable(${PROJECT_NAME} main.cpp)

Q: What is the root cause of the issue?

A: The root cause of the issue is the hardcoded behavior in the CMakeLists.txt file, which forces the runtime library to MultiThreaded when BUILD_SHARED_LIBS is set to FALSE (or OFF).

Q: Why is it not possible to select MultiThreaded or MultiThreadedDLL?

A: The CMAKE_MSVC_RUNTIME_LIBRARY option is not being used to configure the runtime library settings. Instead, the hardcoded behavior is being relied upon.

Q: How can I resolve this issue?

A: There are two alternative approaches to resolve this issue:

Use the CMAKE_MSVC_RUNTIME_LIBRARY Option: Add the following line to your CMakeLists.txt file to specify the runtime library to use:

set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded")

Alternatively, you can use the CMAKE_MSVC_RUNTIME_LIBRARY option to specify the MultiThreadedDLL option:

set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")

Modify the CMakeLists.txt File: Add the following lines to the file to remove the hardcoded behavior:

if(BUILD_SHARED_LIBS)
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreadedDLL")
else()
  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded")
endif()

Q: What are the benefits of using the `CMAKE_MSVC_RUNTIME_LIBRARY` Option?

A: Using the CMAKE_MSVC_RUNTIME_LIBRARY Option provides several benefits, including:

Flexibility: You can configure the runtime library settings based on your project's requirements.
Optimization: You can optimize the performance of your multi-threaded applications by selecting the correct runtime library.
Consistency: You can ensure consistency in your project's build settings by using the CMAKE_MSVC_RUNTIME_LIBRARY Option.

Q: What are the potential drawbacks of using the `CMAKE_MSVC_RUNTIME_LIBRARY` Option?

A: There are no significant drawbacks to using the CMAKE_MSVC_RUNTIME_LIBRARY Option. However, you should be aware of the following:

Additional complexity: Using the CMAKE_MSVC_RUNTIME_LIBRARY Option may add complexity to your CMakeLists.txt file.
Requires CMake 3.20.0 or later: The CMAKE_MSVC_RUNTIME_LIBRARY Option is only available in CMake 3.20.0 or later.

Q: Can I use the `CMAKE_MSVC_RUNTIME_LIBRARY` Option with other build systems?

A: Yes, you can use the CMAKE_MSVC_RUNTIME_LIBRARY Option with other build systems, such as Visual Studio 2019 or later. However, you may need to modify the build system's configuration files to use the CMAKE_MSVC_RUNTIME_LIBRARY Option.

Q: How do I troubleshoot issues related to the `CMAKE_MSVC_RUNTIME_LIBRARY` Option?

A: To troubleshoot issues related to the CMAKE_MSVC_RUNTIME_LIBRARY Option, follow these steps:

Check the CMake version: Ensure that you are using CMake 3.20.0 or later.
Verify the CMAKE_MSVC_RUNTIME_LIBRARY Option: Check that the CMAKE_MSVC_RUNTIME_LIBRARY Option is set correctly in your CMakeLists.txt file.
Check the build system's configuration files: Verify that the build system's configuration files are set up correctly to use the CMAKE_MSVC_RUNTIME_LIBRARY Option.
Consult the CMake documentation: Refer to the CMake documentation for more information on using the CMAKE_MSVC_RUNTIME_LIBRARY Option.

Q: Where can I find more information on using the `CMAKE_MSVC_RUNTIME_LIBRARY` Option?

A: You can find more information on using the CMAKE_MSVC_RUNTIME_LIBRARY Option in the following resources:

CMake documentation: Refer to the CMake documentation for more information on using the CMAKE_MSVC_RUNTIME_LIBRARY Option.
CMake community forums: Post questions and receive answers from the CMake community on the CMake community forums.
CMake tutorials and guides: Follow CMake tutorials and guides to learn more about using the CMAKE_MSVC_RUNTIME_LIBRARY Option.