VCPKG Build Issue: ONNX_USE_LITE_PROTO Always ON

by Alex Johnson 49 views

Unraveling the Mystery of the ONNX_USE_LITE_PROTO Flag in VCPKG Builds

Hey there, fellow tech enthusiasts! Have you ever wrestled with a build that just won't behave? I recently encountered a peculiar issue while working with VCPKG and the ONNX Runtime, specifically concerning the ONNX_USE_LITE_PROTO flag. It seemed like no matter what I did, this flag kept getting set to ON during the build process, leading to some unexpected behavior and head-scratching moments. In this article, we'll dive deep into this issue, explore the intricacies of the CMakeCache.txt file, and see how the libprotobuf-lited.a library plays a role. We'll also touch upon the implications of bumping ONNX to version 1.20.0 and how it affected the build process. Let's get started and unravel this build mystery together!

The Core of the Problem: ONNX_USE_LITE_PROTO Always ON

The central issue revolves around the ONNX_USE_LITE_PROTO flag within the VCPKG build environment. The observed behavior is that the flag consistently defaults to ON, irrespective of attempts to modify its value. This behavior manifests in the CMakeCache.txt file, a crucial component of CMake builds. This file stores cached variables and configurations, and in this case, it stubbornly retains ONNX_USE_LITE_PROTO=ON. Even after trying to revert changes related to this flag, as documented in the Microsoft ONNX Runtime repository, the build persistently sets this flag to ON. This consistency suggests an underlying mechanism or configuration that overrides any manual adjustments. This unexpected behavior can lead to complications, especially when specific configurations or builds are required that deviate from the default lite protobuf implementation. The root cause can stem from the build scripts or dependencies, which might be hardcoding or implicitly setting the flag. Another potential factor could be within the VCPKG port files for ONNX Runtime, which might be inadvertently setting this flag during configuration. Understanding this issue is essential for anyone building or integrating ONNX Runtime with VCPKG, as it affects the build's outcome and the deployed artifacts. It is also important to note that the issue surfaced while upgrading to ONNX version 1.20.0, indicating that newer versions or updates might have exacerbated this behavior.

Deep Dive into CMakeCache.txt and its Implications

The CMakeCache.txt file is the heart of CMake builds, holding all the settings, paths, and configurations used during the build process. When dealing with the ONNX_USE_LITE_PROTO flag, this file becomes a critical point of inspection. Its behavior is directly tied to the final built product. The file's role is to cache the configuration, so subsequent builds execute more efficiently. When a flag like ONNX_USE_LITE_PROTO is set, it directly influences which parts of the ONNX Runtime are compiled and linked. A value of ON means the build will use the lite protobuf implementation, which is a streamlined version of the protocol buffers. This can result in smaller binaries and faster build times. However, if this setting is unexpected or unwanted, it can lead to compatibility issues or missing features if the full protobuf implementation is required. The CMakeCache.txt is essentially the single source of truth for the CMake build. If the flag consistently appears as ON here, it strongly suggests a hardcoded setting or a default behavior from within the build system. Understanding the content of CMakeCache.txt is crucial for debugging and troubleshooting. Users need to carefully examine this file to determine where the ONNX_USE_LITE_PROTO flag is being set and what's overriding their desired settings. This often involves tracing the build scripts, checking environment variables, and scrutinizing any VCPKG-specific configurations.

To thoroughly investigate, one would need to:

  1. Examine the CMake scripts: Review the CMakeLists.txt files in the ONNX Runtime and VCPKG port directories to find where the flag is being set.
  2. Check for environment variables: Look for environment variables that could be affecting the build.
  3. Inspect the VCPKG port files: The VCPKG port files often contain specific configurations, so checking these is essential.
  4. Reproduce the issue: The issue needs to be consistently reproducible to ensure that the investigation is on the right track.

The Role of libprotobuf-lited.a and Its Potential Impact

Another critical piece of the puzzle is libprotobuf-lited.a. This static library, often created during the build, is a key component when the ONNX_USE_LITE_PROTO flag is set to ON. This library contains a streamlined version of the protobuf implementation. The presence of libprotobuf-lited.a suggests that the lite protobuf variant is being built and linked into the ONNX Runtime. This choice might be deliberate, optimizing for size and speed, but it can create problems. If the build system consistently produces this library without providing a way to use the full protobuf, then the user may face limitations. While it might be created, its actual usage during the build process is not guaranteed. There is a possibility that this library is not being used in the final linked product, or its presence doesn't reflect the desired build configuration. However, if the build relies on features present only in the full protobuf implementation, the presence of libprotobuf-lited.a and the setting of ONNX_USE_LITE_PROTO=ON become potential sources of error and incompatibility. The key is to verify how the build system integrates libprotobuf-lited.a. Users should check the linking process to see if the library is correctly linked to the ONNX Runtime components. They should also compare it to the full protobuf implementation to ensure no critical features are missing. This comprehensive assessment ensures the build meets all required functional and performance standards.

Potential Issues:

  • Incompatibility: Lite protobuf might lack certain features present in the full protobuf implementation, leading to runtime errors.
  • Size Reduction: While lite versions can reduce binary size, the performance benefits are not always significant.
  • Configuration Complexity: Managing different protobuf implementations can add complexity to the build process.

Bumping ONNX to 1.20.0 and the Resulting Build Challenges

The upgrade to ONNX version 1.20.0 appears to have brought the ONNX_USE_LITE_PROTO issue to the forefront. This suggests that changes introduced in this version or its dependencies might have triggered or exacerbated the problem. Specifically, the build only succeeds when the ONNX_USE_LITE_PROTO:BOOL=ON is explicitly set. This behavior indicates that the default configuration in version 1.20.0 may be different from prior versions, and the build system might be more sensitive to the setting of this flag. During the upgrade process, any modifications to the build scripts, dependencies, or default configurations could have introduced these inconsistencies. Identifying these changes is crucial for resolving the issue. This could involve examining the ONNX Runtime release notes for version 1.20.0 and reviewing the corresponding commits. The user might need to adjust the VCPKG port file to align with the new version’s requirements. A detailed comparison of the build process between different ONNX versions could reveal where the setting of ONNX_USE_LITE_PROTO is being influenced. This includes tracking down any conditional logic that might be triggered by the new version. The fix involved explicitly setting the flag, but a more robust solution might require a deeper understanding of the underlying causes and potentially adjusting the build scripts to provide greater flexibility and control over the configuration. Understanding the impact of the version upgrade is a key element in resolving the issue and ensuring a stable build process.

Troubleshooting Steps:

  1. Review the Release Notes: Check the ONNX Runtime release notes for version 1.20.0 to understand any changes related to protobuf or build configurations.
  2. Compare Build Scripts: Compare the build scripts and CMake files between the previous and current versions to identify changes impacting the flag.
  3. Inspect Dependencies: Verify dependencies, particularly those related to protobuf, for any updates or changes that might influence the build.
  4. Test Configurations: Experiment with different build configurations, including enabling and disabling the ONNX_USE_LITE_PROTO flag, to determine the exact impact.

Conclusion: Navigating the VCPKG Build Maze

As we have seen, the ONNX_USE_LITE_PROTO flag and its behavior within the VCPKG build environment can present significant challenges. The consistent setting of this flag to ON, along with the creation of libprotobuf-lited.a, requires careful examination of the CMake scripts, environment variables, and VCPKG configurations. The upgrade to ONNX version 1.20.0 further highlights the importance of understanding these intricacies. To resolve these issues, developers should meticulously trace the build process, identify the origin of the flag setting, and ensure that the build configuration aligns with their specific requirements. By understanding the role of CMakeCache.txt, the implications of using libprotobuf-lited.a, and the impact of ONNX version upgrades, developers can successfully navigate the build maze. Further investigation, including examining the specific changes introduced in ONNX Runtime version 1.20.0 and analyzing the VCPKG port file, will be crucial in ensuring that the build is flexible and meets all necessary functional and performance requirements. Remember to consult the official ONNX Runtime documentation for detailed instructions and best practices.

For more detailed information and further reading, check out the ONNX Runtime documentation at https://onnxruntime.ai/