# Build Issue
##

### Protobuf (protoc) Version Conflict
<br>

#### Problem


When installing dependencies like ROS or OpenCV on a system (e.g., UPC), or if an older version of protoc is pre-installed, the following error might occur during pip install or cmake:

<br>

#### Error Message:

```bash
# error This file was generated by an older version of protoc which is
```

This happens because a lower-priority protoc version is being used instead of the required version.

<br>

#### Solution:

1. Download the Correct protoc Version
- Visit the 
<a href="https://github.com/protocolbuffers/protobuf/releases/tag/v21.12" target="_blank" rel="noopener noreferrer">
  Protobuf Releases
</a>
 page and download the appropriate protoc version based on your architecture:
    - For ARM (e.g., UPC): protoc-21.12-linux-aarch_64.zip
    - For x86: protoc-21.12-linux-x86_64.zip

<br>

2. Extract the Archive
- Extract the downloaded .zip file:

```bash
unzip protoc-21.12-linux-YOUR_ARCHITECTURE.zip -d protoc-21.12
```

<br>

3. Update PATH

- Set the extracted protoc binary directory at the beginning of your PATH environment variable:
- Replace /path/to/extracted with the actual path where the archive was extracted.
- By placing the required protoc version at the start of the PATH environment variable, the system prioritizes it over older versions already installed.

```bash
export PATH="/path/to/extracted/protoc-21.12/bin:$PATH"
```

- Verification
    - Run the following command to confirm the correct version of protoc is being used:

```bash
nvidia@tegra-ubuntu:~$ protoc --version
libprotoc 3.21.12
```

<br>

4. Retry Build or Installation After updating the PATH, retry the cmake or pip command. The issue should now be resolved.

---
### CMake Preset Error
<br>

#### Problem:

An error occurs when running CMake with the `--preset option`: "The source directory does not exist."

<br>

#### Error Message:

```bash
user@hostname:~/project-directory$ cmake --preset conan-release
CMake Error: The source directory "/home/user/project-directory/conan-release" does not exist.
Specify --help for usage, or press the help button on the CMake GUI.
```

<br>

#### Solution:
<br>

#### Check CMake Version:

- This error is often caused by using an older CMake version. Ensure that your CMake version is 3.23 or higher.

```bash
cmake --version
```

- If the version is outdated, refer to the installation process in the CMake installation section to upgrade to the latest version.

---
In most cases, the issue can be resolved by following the above steps. If the problem persists, review the following items.

<br>

#### Additional Checks:

- **Preset Path**: Make sure you are running the CMake command from the project's root directory.
- **Preset Name**: Verify that the preset name defined in the `CMakePresets.json` file is correct.
- **Git Submodule**: Ensure that the submodules are properly initialized when cloning the project.

```bash
git submodule update --init --recursive
```

<br>

#### References:

- For more detailed information, refer to the 
<a href="https://docs.conan.io/2/examples/tools/cmake/cmake_toolchain/build_project_cmake_presets.html" target="_blank" rel="noopener noreferrer">
  Building Projects Using CMake Presets
</a>
 documentation.