description: "Describes the Microsoft C and C++ (MSVC) linker error LNK1104, its causes, and possible solutions."

ms.date: "12/13/2019"

This error is reported when the linker fails to open a file, either for reading or for writing. The two most common causes of the issue are:

- your program is already running or is loaded in the debugger, and

- your library paths are incorrect, or aren't wrapped in double-quotes.

There are many other possible causes for this error. To narrow them down, first check what kind of file *filename* is. Then, use the following sections to help identify and fix the specific issue.

When *filename* is your executable's name, or an associated .pdb file, see if your application is already running. Then check whether it's loaded in a debugger. To fix this issue, stop the program and unload it from the debugger before building it again. If the app is open in another program, such as a resource editor, close it. If your program is unresponsive, you may need to use Task Manager to end the process. You might also need to close and restart Visual Studio.

There are no Spectre-mitigated libraries for Universal Windows (UWP) apps or components. If the error message includes *vccorlib.lib*, you may have enabled [/Qspectre](../../build/reference/qspectre.md) in a UWP project. Disable the **/Qspectre** compiler option to fix this issue. In Visual Studio, change the **Spectre Mitigation** property. It's found in the **C/C++** > **Code Generation** page of the project **Property Pages** dialog.

If you build a project copied from another computer, the library installation locations may be different. For command-line builds, verify the LIB environment variable and library paths are set correctly for the build. In Visual Studio, you can see and edit the current library paths set in the Property pages for your project. In the **VC++ Directories** page, choose the drop-down control for the **Library Directories** property, then choose **Edit**. The **Evaluated value** section of the **Library Directories** dialog lists the current paths searched for library files. Update these paths to point to your local libraries.

This error can occur when the Visual Studio path to the Windows SDK is out of date. It may happen if you install a newer Windows SDK independently of the Visual Studio installer. To fix it in the IDE, update the paths specified in the [VC++ Directories property page](../../build/reference/vcpp-directories-property-page.md). Set the version in the path to match the new SDK. If you use the Developer Command Prompt, update the batch file that initializes the environment variables with the new SDK paths. This problem can be avoided by using the Visual Studio installer to install updated SDKs.

- You may have installed a 32-bit version of the library but you're building for 64 bits, or the other way around.

To fix a path issue for command-line builds, verify the LIB environment variable is set. Make sure it includes paths for all the libraries you use, and for every configuration you build. In the IDE, the library paths get set by the **VC++ Directories** > **Library Directories** property. Make sure all the directories that contain the libraries you need are listed here, for every configuration you build.

Make sure you install every version of the library you need for the configurations you build. Consider using the [vcpkg](../../vcpkg.md) package management utility to automate the installation and setup for many common libraries. When you can, it's best to build your own copies of third-party libraries. Then you're sure to have all the libraries' local dependencies, built for the same configurations as your project.

You may see this error if *filename* doesn't exist yet when the linker tries to access it. It can happen when one project depends on another in the solution, but the projects build in the wrong order. To fix this issue, make sure your project references are set in the project that uses the file. Then the missing file gets built before it's required. For more information, see [Adding references in Visual Studio C++ projects](../../build/adding-references-in-visual-cpp-projects.md) and [Managing references in a project](/visualstudio/ide/managing-references-in-a-project).

If you see the filename *C:\\Program.obj* in the error message, wrap your library paths in double quotes. This error happens when an unwrapped path that begins with *C:\\Program Files* gets passed to the linker. Unwrapped paths may also cause similar errors. Typically, they show an unexpected .obj file in the root of your drive.

To fix this issue in the IDE, add double-quotes as necessary to the following properties for your project:

If you're using a parallel build option, Visual Studio may have locked the file on another thread. To fix this issue, verify the same code object or library isn't built in multiple projects. Use build dependencies or project references to pick up built binaries in your project.

You may see this error when the path for *filename* expands to more than 260 characters. If needed, rearrange your directory structure or shorten your folder and file names to shorten the paths.

This error can occur if you have insufficient file permissions to access *filename*. It may happen if you use an ordinary user account to access library files in protected system directories. Or, if you use files copied from other users that still have their original permissions set. To fix this issue, move the file to a writeable project directory. If the moved file has inaccessible permissions, run the takeown.exe command in an Administrator command window to take ownership of the file.

When none of the issues listed here apply, you can use the feedback tools in Visual Studio for help. In the IDE, go to the menu bar and choose **Help > Send Feedback > Report a Problem**. Or, submit a suggestion by using **Help > Send Feedback > Send a Suggestion**. You can also use the Visual Studio C++ [Developer Community](https://developercommunity.visualstudio.com/spaces/62/index.html)) website. Use it to search for answers to questions and ask for help. For more information, see [How to report a problem with the Visual C++ toolset or documentation](../../overview/how-to-report-a-problem-with-the-visual-cpp-toolset.md).

If you've discovered a new way to fix this issue that we should add to this article, let us know. You can send us feedback by using the button below for **this page**. Use it to create a new issue in our [C++ documentation GitHub repo](https://github.com/MicrosoftDocs/cpp-docs/issues). Thanks!