Help menu, or open the Technical Support help file for more information INTERNAL COMPILER ERROR in ‘C: Program Files (x86) Microsoft Visual Studio 14.0 VC bin x86_amd64 cl.exe’ Please choose the Technical Support command on the Visual C++ Help menu, or open the Technical Support help file for more information.

First, I'm Eric Knox, the Visual Studio engineering manager who currently is responsible for VS installation. This post is intended as a proactive question + answer to hopefully help folks who are impacted by VS2015 Update 1 before my team can get a fix deployed. Problem Description Since shipping VS 2015 Update 1 very recently, I've heard a number of reports of VS not behaving properly after the update installed. Some symptoms I've heard of are error messages saying one or more of: • Could not load file or assembly ‘System.Collections.Immutable, Version=1.1.36.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. The located assembly’s manifest definition does not match the assembly reference.

(Exception from HRESULT: 0x80131040)] • Object reference not set to an instance of an object. • The 'JavaScriptWebExtensionsPackage' package did not load correctly.

The problem may have been caused by a configuration change or by the installation of another extension. You can get more information by examining the file C: Users AppData Roaming Microsoft VisuaIStudio 14.0 ActivityLog.xml'. Restarting Visual Studio could help resolve this issue. Continue to show this error message? Thanks to some help from some folks in the community (thanks Sergey!), we've tracked it down to the fact that the Update installer doesn't always upgrade VS' devenv.exe.config file. Am I affected? To figure out if your machine is impacted, you can check the install logs to know for sure.

To do so, open a command prompt and paste in this: pushd%temp% find /I 'Common7 IDE devenv.exe.config' *vsupdate*.log findstr -i overwrite If you see 'Won't Overwrite;' in the output, then your machine *is* impacted. If you see 'Overwrite;', then any issues you are experiencing should be unrelated to this thread. Here's sample output if your machine is affected: MSI (s) (CC:60) [08:46:49:362]: File: C: Program Files (x86) Microsoft Visual Studio 14.0 Common7 IDE devenv.exe.config; Won't Overwrite; Won't patch; Existing file is unversioned but modified Output if your machine is *not* affected: MSI (s) (7C:34) [20:39:50:792]: File: C: Program Files (x86) Microsoft Visual Studio 14.0 Common7 IDE devenv.exe.config; Overwrite; Won't patch; Existing file is unversioned and unmodified - hash doesn't match source file How do I fix this? If your machine did not correctly install the VSUpdate 1 config file, you can remedy this by doing the following: 1. Download the correct VSUpdate 1 config to a folder on your machine from this link: 2. Open an admin command prompt and run these steps (assuming you installed to the default location): cd '%ProgramFiles(x86)% Microsoft Visual Studio 14.0 Common7 IDE' ren devenv.exe.config devenv.exe.config.backup copy. Devenv.exe.config devenv /UpdateConfiguration When will this be fixed? Mac cosmetics.

My engineering team is working on a fix right now with the expectation of publishing a servicing fix by the end of this week at latest. The challenge I have though is that my team's fix will only work for new installs. I don't have a mechanism in place for VS to detect that it is in this state and somehow self-repair. That's why I'm posting this manual fix-up script for folks who have been impacted in the short term.