Finding a VS Code Memory Leak

(randomascii.wordpress.com)

80 points | by brucedawson 14 hours ago

8 comments

  • delta_p_delta_x 52 minutes ago
    Great analysis, but the solution is so simple: RAII.

    And this is offered as `unique_process_handle`[1] in the Windows Implementation Library (WIL)[2].

    This is a fantastic addition to the Windows developer's toolkit, which everyone should be using from the outset. The Windows C API is unnecessarily verbose (although this can be said of any OS, Windows' is particularly bad), and simple mistakes can and will happen.

    Let RAII help you, let the mighty close-scope token `} ` be your best friend.

    [1]: https://github.com/microsoft/wil/blob/1f20cd086e07b9be54e70d...

    [2]: https://github.com/microsoft/wil

  • brucedawson 14 hours ago
    In 2021 I found an invisible memory leak in a tool (VS Code) that I have never used. This is the story of how.
  • criemen 11 hours ago
    > For obscure technical reasons they are always multiples of four.

    Why did I know that that link went to Raymond Chen before clicking it... That man is a treasure.

  • aborsy 2 hours ago
    The code base for VSCode seems to be huge. With plug-ins, bloat, all the different things that it does, and large number of installations, it seems an ideal target for vulnerabilities and supply chain attacks.

    Anyone knows more the level of risk?

  • userbinator 5 hours ago
    In this case I noticed that the process IDs on her system had seven digits.

    I believe on Windows 9x, process IDs are actual kernel addresses (pointers to the process structure), and thus always have 10 digits.

  • anonymousDan 12 hours ago
    Re the last wish, isn't that exactly what ulimit is for?
    • diath 11 hours ago
      On Linux, yes, but this was Windows-specific code and Windows has no equivalent mechanism to ulimits.
      • Arnavion 7 hours ago
        There are job objects which are similar to Linux cgroups, including the ability to set a limit on the number of processes. But I'm not sure if that limit will be tripped in this case or not because the child processes have exited, whereas the job object parameter is specifically called LIMIT_ACTIVE_PROCESS

        https://learn.microsoft.com/en-us/windows/win32/procthread/j...

        https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns...

        • diath 6 hours ago
          OpenProcess retrieves a handle to an existing process rather than creating a process so it won't be governed by JOB_OBJECT_LIMIT_ACTIVE_PROCESS, the bug here is that it's leaking handles, not processes.
          • Arnavion 5 hours ago
            Ah yes, in that case the relevant limit would be one on total handles, which doesn't seem to exist.
  • anonymars 12 hours ago
    > Sometimes I think it would be nice to have limits on resources in order to more automatically find mistakes like this

    I was actually fairly disappointed when Visual Studio (not code) went to 64-bit. Because I knew its memory usage was now going to be unconstrained. Still way better than the unapologetic gluttony of Rider but experiences showed it to be a bit leaky over time (tip: Ctrl-Alt-Shift-F12 twice does a full garbage collection https://learn.microsoft.com/en-us/visualstudio/ide/visual-st...)

    Also remember that all your references (pointers) are going to double in size so right off the bat it will use more, potentially a lot more depending on how reference-heavy your data is

    • DanielHB 2 hours ago
      > I was actually fairly disappointed when Visual Studio (not code) went to 64-bit.

      Keep stuff on 32bit to ensure memory leaks and feature bloat are caught early, genius.

      Seriously though, that might be a quick and dirty way to get an application with a hard-limit on memory for testing.

  • seivan 12 hours ago
    [dead]