macOS: High CPU Usage (looping `update_file_if_needed`)

Bug type: Language Service

Describe the bug

• OS and Version:
  
• VS Code Version:
  
• C/C++ Extension Version:
  v1.6.0

Sometime after starting vscode, the cpptools process will jump to 100% CPU usage and stay there until the windows is reloaded.
The project is for embedded devices, and is therefore using a cross-compiler (arm-none-eabi-gcc). Intellisense configuration is through an autogenerated compile_commands.json. The project is based on Zephyr RTOS (https://github.com/zephyrproject-rtos/zephyr). The root folder (ignoring compiler headers) is approximately 40k files.

Code sample and logs

• Configurations in c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Zephyr",
            "cStandard": "c99",
            "compilerPath": "/Users/<user>/code/gcc-arm-none-eabi/bin/arm-none-eabi-gcc",
            "intelliSenseMode": "gcc-x64",
            "compileCommands": "${workspaceFolder}/build/compile_commands.json",
            "includePath": [
                "zephyr/include",
                "${workspaceFolder}/build/zephyr/include/generated"
            ]
        }
    ],
    "version": 4
}

• Logs from running C/C++: Log Diagnostics from the VS Code command palette

    "C_Cpp.loggingLevel": "7",

update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/x86/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/arm64/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/arm/aarch32/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/arc/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/nios2/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/riscv/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/xtensa/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/posix/arch.h
  Same time stamp: 1630475297
update_file_if_needed: /Users/<user>/zephyr/zephyr/include/arch/sparc/arch.h
  Same time stamp: 1630475297

Over a minute or so of just watching the logs, there were approximately 400 thousand lines like the above.
Not all files were being checked. Files that were checked were checked about 80 times each.

Additional context

Call stack of cpptools process.

cpptools プロセスのコールスタックと、C/C++: Log Diagnostics に出力される update_file_if_needed の繰り返し診断から始めます。Zephyr ワークスペース、arm-none-eabi-gcc、自動生成された compile_commands.json を使用して macOS 上で再現します。繰り返されるファイルチェックが停止し、cpptools が CPU 使用率 100% を維持しなくなれば完了です。