Error MT4109 (VS 2017 Professional): Failed to compile the generated registrar code.

[vinicius-stutz]

I can't compile my code using Xamarin Forms (but only on iOS). I am using Visual Studio 2017 v15.9.16, Windows 10, Xamarin Forms project (Android and iOS). I already installed Xamarin Forms 4.2.0.815419 and preview 4.3.0.819712-pre2, but nothing solved. This error began to occur after Mac upgraded XCode to version 11.

Steps to Reproduce

1. I deleted the bin and obj folders from the iOS project;
2. Clean iOS project;
3. Build iOS project.

Expected Behavior

Build without error.

Actual Behavior

Build with error "MT4109: Failed to compile the generated registrar code. Please file a bug report at http://bugzilla.xamarin.com."

Environment

Microsoft Visual Studio Professional 2017 
Version 15.9.16
VisualStudio.15.Release/15.9.16+28307.858
Microsoft .NET Framework
Version 4.8.03752

Installed Version: Professional

Visual C++ 2017   00369-60000-00001-AA934
Microsoft Visual C++ 2017

Add New File   3.5.134
The fastest and easiest way to add new files to any project - including files that start with a dot

AddNuSpecCommand Extension   1.0
AddNuSpecCommand Visual Stuido Extension Detailed Info

ASP.NET and Web Tools 2017   15.9.04012.0
ASP.NET and Web Tools 2017

ASP.NET Core Razor Language Services   15.8.31590
Provides languages services for ASP.NET Core Razor.

ASP.NET Web Frameworks and Tools 2012   4.0.30625.0
For additional information, visit https://www.asp.net/

ASP.NET Web Frameworks and Tools 2017   5.2.61435.0
For additional information, visit https://www.asp.net/

Azure App Service Tools v3.0.0   15.9.03024.0
Azure App Service Tools v3.0.0

Bundler & Minifier   2.8.396
Adds support for bundling and minifying JavaScript, CSS and HTML files in any project.

C# Tools   2.10.0-beta2-63501-03+b9fb1610c87cccc8ceb74a770dba261a58e39c4a
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Common Azure Tools   1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

CSS Tools   1.1.23
Provides additional features to the CSS editor in Visual Studio.

EditorConfig Language Service   1.17.260
Language service for .editorconfig files.

EditorConfig helps developers define and maintain consistent coding styles between different editors and IDEs.

Extensibility Message Bus   1.1.49 (remotes/origin/d15-8@ee674f3)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

File Icons   2.7
Adds icons for files that are not recognized by Solution Explorer

File Nesting   2.6.85
Automatically nest files based on file name and enables developers to nest and unnest any file manually

GhostDoc   19.2.19200.0
Generate XML Comments from your code, maintain clean and up-to-date documentation, produce help documentation in multiple formats, use intelligent source code Spell Checker in Visual Studio.

GitFlow.VS.Extension   1.0
Visual Studio extension that integrates GitFlow

HTML Tools   1.0.3
Productivity tools for the HTML editor

Image Optimizer   4.0.132
Uses industry standard tools to optimize any JPEG, PNG and Gifs - including animated Gifs. Can do both lossy and lossless optimization.

Image Sprites   1.4.58
Boost your website's performance by creating image sprites to reduce the amount of HTTP requests needed.

JavaScript Language Service   2.0
JavaScript Language Service

JavaScript Project System   2.0
JavaScript Project System

JavaScript UWP Project System   2.0
JavaScript UWP Project System

Markdown Editor   1.12.236
A full featured Markdown editor with live preview and syntax highlighting. Supports GitHub flavored Markdown.

Material icons generator   1.8.0
This plugin help you to add material design icons to your Android, iOS or UWP project

Microsoft Azure Tools   2.9
Microsoft Azure Tools for Microsoft Visual Studio 2017 - v2.9.20417.1

Microsoft Continuous Delivery Tools for Visual Studio   0.4
Simplifying the configuration of Azure DevOps pipelines from within the Visual Studio IDE.

Microsoft JVM Debugger   1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Microsoft Library Manager   1.0
Install client-side libraries easily to any web project

Microsoft MI-Based Debugger   1.0
Provides support for connecting Visual Studio to MI compatible debuggers

Microsoft Visual C++ Wizards   1.0
Microsoft Visual C++ Wizards

Microsoft Visual Studio Tools for Containers   1.1
Develop, run, validate your ASP.NET Core applications in the target environment. F5 your application directly into a container with debugging, or CTRL + F5 to edit & refresh your app without having to rebuild the container.

Microsoft Visual Studio VC Package   1.0
Microsoft Visual Studio VC Package

MLGen Package Extension   1.0
MLGen Package Visual Studio Extension Detailed Info

Mono Debugging for Visual Studio   4.13.12-pre (9bc9548)
Support for debugging Mono processes with Visual Studio.

Node.js Tools   1.4.30613.3 Commit Hash:1e6f79a5385c9083fd034ccdfc4f64f58dea9e7b
Adds support for developing and debugging Node.js apps in Visual Studio

NuGet Package Manager   4.6.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.

Open Command Line   2.4.226
2.4.226

Package Installer   2.0.103
Makes it easier, faster and more convenient than ever to install Bower, npm, Yarn, JSPM, TSD, Typings and NuGet packages to any project

Package Security Alerts   1.0.22
Identifies npm and Bower packages that contains known security vulnerabilities to ensure your project is always using the most secure package versions.

PowerShell Pro Tools for Visual Studio   1.0
A set of tools for developing and debugging PowerShell scripts and modules in Visual Studio.

Project File Tools   1.0.1
Provides Intellisense and other tooling for XML based project files such as .csproj and .vbproj files.

ProjectServicesPackage Extension   1.0
ProjectServicesPackage Visual Studio Extension Detailed Info

ResourcePackage Extension   1.0
ResourcePackage Visual Studio Extension Detailed Info

ResourcePackage Extension   1.0
ResourcePackage Visual Studio Extension Detailed Info

SettingsWindow Extension   1.0
SettingsWindow Visual Studio Extension Detailed Info

SQL Server Data Tools   15.1.61906.03120
Microsoft SQL Server Data Tools

TypeScript Tools   15.9.30718.2001
TypeScript Tools for Microsoft Visual Studio

Visual Basic Tools   2.10.0-beta2-63501-03+b9fb1610c87cccc8ceb74a770dba261a58e39c4a
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual F# Tools 10.2 for F# 4.5   15.8.0.0.  Commit Hash: 6e26c5bacc8c4201e962f5bdde0a177f82f88691.
Microsoft Visual F# Tools 10.2 for F# 4.5

Visual Studio Code Debug Adapter Host Package   1.0
Interop layer for hosting Visual Studio Code debug adapters in Visual Studio

Visual Studio Tools for Containers   1.0
Visual Studio Tools for Containers

Visual Studio Tools for Universal Windows Apps   15.0.28307.858
The Visual Studio Tools for Universal Windows apps allow you to build a single universal app experience that can reach every device running Windows 10: phone, tablet, PC, and more. It includes the Microsoft Windows 10 Software Development Kit.

VisualStudio.Mac   1.0
Mac Extension for Visual Studio

Web Compiler   1.12.394
Compiler for LESS, Sass and CoffeeScript files

Web Essentials 2017   2.0.44
The easiest way to set up Visual Studio for the ultimate web development experience. Requires Visual Studio 2017 Update 8 or newer

Xamarin   4.12.3.83 (d15-9@23fa80172)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   4.16.30 (e0af99a34)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Templates   1.1.128 (6f5ebb2)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   9.1.7.0 (HEAD/ba9da7a76)
Xamarin.Android Reference Assemblies and MSBuild support.

Xamarin.iOS and Xamarin.Mac SDK   12.4.0.64 (9c8d8e0)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

ZenCoding   1.2.12
Provides ZenCoding for the HTML Editor - full support for static HTML, Razor and WebForms.

Build Logs

Only error lines:

1. /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS13.0.sdk/System/Library/Frameworks/Photos.framework/Headers/PHImageManager.h:17:47: error: expected identifier or '{'
2. /Users/dsv/Library/Caches/Xamarin/mtbs/builds/AppUBC.iOS/fd8879980a0f70bd231774370f90096a/obj/iPhone/Debug/mtouch-cache/registrar.h:45:9: fatal error: 'WatchKit/WatchKit.h' file not found
3. error MT4109: Failed to compile the generated registrar code. Please file a bug report at http://bugzilla.xamarin.com

[screamingworld]

I have the same similar problem, after updating to xcode 11 and deleting all generated files. At first the simulator no more work and now after deleting the files - nothing is working.
--> Error Failed to compile the generated registrar code.

[screamingworld]

Ok - I could fix the issue...
So you have to update your VS (in my case 2019) to the newest Version.
Or may be the newest Xamarin Components for 2017.
An alternative could be downgrade xcode https://medium.com/@tseboho/how-to-downgrade-xcode-4359df5158d5
hope this helps...

[rolfbjarne]

Xamarin.iOS and Xamarin.Mac SDK 12.4.0.64 (9c8d8e0)

This is an old version of Xamarin.iOS. Please upgrade to the latest stable version, and your problem will be fixed.

[vinicius-stutz]

Xamarin.iOS and Xamarin.Mac SDK 12.4.0.64 (9c8d8e0)

This is an old version of Xamarin.iOS. Please upgrade to the latest stable version, and your problem will be fixed.

@rolfbjarne, I have updated Xamarin Forms to the latest available version, but it does not bring me update to the latest available version of Xamarin iOS. Sorry if it's ignorance or lack of knowledge on my part.

[rolfbjarne]

@vinicius-stutz I believe you have to update to Visual Studio 2019, and then you'll get the updated Xamarin.iOS as well. AFAIK the newest version does not support VS 2017.

[screamingworld]

@vinicius-stutz I believe you have to update to Visual Studio 2019, and then you'll get the updated Xamarin.iOS as well. AFAIK the newest version does not support VS 2017.

Or downgrade your xCode to Version 10.3