configuring QT with webassembly issue: failed on Qt6ProtobufTools, WrapProtoc not found

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05-10-2024

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Conquering the "WrapProtoc Not Found" Error When Configuring Qt with WebAssembly

Building Qt applications for the web using WebAssembly can be a powerful approach. However, you might encounter a roadblock during the configuration process: the "WrapProtoc not found" error, specifically related to the Qt6ProtobufTools. This article aims to help you understand this error and guide you through the solution.

The Problem:

The Qt6ProtobufTools library is a crucial component for interacting with Protocol Buffers (protobuf) in your Qt applications. This library relies on the protoc tool, which is a compiler for protobuf definitions. The error "WrapProtoc not found" arises when Qt's configuration process fails to locate the protoc executable, which is essential for building the ProtobufTools.

Scenario:

Imagine you're building a Qt project with the intention of deploying it as a WebAssembly application. You begin by configuring Qt with WebAssembly support, but during this process, the configuration fails with the error message:

...
CMake Error at protobuf/cmake/FindProtobuf.cmake:103 (message):
  WrapProtoc not found.
Call Stack (most recent call first):
  protobuf/CMakeLists.txt:77 (find_package)
  qtbase/src/plugins/platforms/webengine/CMakeLists.txt:460 (add_subdirectory)
  qtbase/src/CMakeLists.txt:149 (add_subdirectory)
  CMakeLists.txt:18 (add_subdirectory)
...

This error signifies that the configuration process cannot locate the protoc executable, preventing the successful build of the ProtobufTools.

Analysis and Solutions:

The issue arises because the protoc tool is not included by default in the WebAssembly Qt configuration. Here's a step-by-step guide to overcome this:

1. Install Protobuf: Ensure you have the Protobuf development environment installed on your system. This usually includes the protoc compiler:

   • Linux:

     sudo apt-get install protobuf-compiler
     

   • macOS:

     brew install protobuf
     

   • Windows: Download and install Protobuf from the official website (https://github.com/protocolbuffers/protobuf/releases).

2. Configure Qt with protoc Path: When configuring Qt for WebAssembly, provide the path to the protoc executable. Here's how you can do it:

   • Using cmake:

     cmake -DPROTOBUF_PROTOC_EXECUTABLE=/path/to/protoc ...
     

     Replace /path/to/protoc with the actual path to the protoc executable on your system.

   • Using Qt's configuration tool (Qt Creator):

     You may have a protoc path configuration option within Qt Creator's project settings. Refer to the Qt documentation for specific instructions on your version.

3. Verify Installation: After configuring Qt with the protoc path, try configuring again. This time, the ProtobufTools should build successfully without the error.

Additional Notes:

• Qt WebAssembly Support: Ensure you have properly configured Qt for WebAssembly development. The necessary WebAssembly components, including Emscripten, should be installed and configured for a smooth experience.
• Protobuf Language Support: If you're working with languages other than C++, ensure that the Protobuf libraries and tools are available for your target language.

Conclusion:

Successfully configuring Qt with WebAssembly requires navigating potential roadblocks, like the "WrapProtoc not found" error. By understanding the error's origin and following the steps outlined in this article, you can overcome this challenge and integrate the ProtobufTools into your Qt projects.

Further Reading and Resources:

• Protobuf Documentation
• Qt for WebAssembly Documentation
• Qt WebAssembly Build Instructions

By utilizing these resources and applying the guidance provided, you'll be well-equipped to build impressive Qt WebAssembly applications that leverage the power of Protocol Buffers.