Defrag Tools #184 - JavaScript in WinDbg Preview

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In this episode of Defrag Tools, we continue our series on the new WinDbg Preview. Andrew Richards is joined by Bill Messmer to talk about the updated scripting engine.

Related Links:

WinDbg Preview (download from Microsoft Store)
Documentation for WinDbg Preview (Dev Center)
Announcement blog post

Related Episodes:

Defrag Tools #138 - Debugging - 'dx' Command Part 1
Defrag Tools #139 - Debugging - 'dx' Command Part 2
Defrag Tools #169 - Debugging Tools For Windows Team
Defrag Tools #170 - Debugger - JavaScript Scripting
Defrag Tools #182 - WinDbg Preview Part 1
Defrag Tools #183 - WinDbg Preview Part 2




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The Discussion

  • User profile image

    I want to report an WinDbg-issue concerning the execution
    of a javascript-function as a breakpoint-command.
    This observation was made in WinDbg 10.0.16267.1000 X86
    and also in the current WinDbg Preview
    with a native C++ program.
    ++++ Test Setup ++++
    In my javascript-file I have the following function:
    function test()
       var ctl = host.namespace.Debugger.Utility.Control;
        host.diagnostics.debugLog(">>> Test\n");
    Then I define  a breakpoint-command to call this javascript-function:
    bs 0 "dx @$scriptContents.test()"
    ++++ Test Result ++++
    The output ">>> Test" is only shown the first time
    when breakpoint 0 is hit.
    Subsequently hitting breakpoint 0 does not
    produce any output.

    --> WinDbg:
    After several hits, windbg breaks at breakpoint 0.
    When I stop the debug process (Shift-F5)
    WinDbg crashes in ChakraCore.

    --> WinDbg Preview: stack overflow

    ++++ Remarks ++++
    1) Doing the analogous test with "old style" windbg-commands works:

    bs 0 ".printf \">>> Test\\n\";g;"

    2) Calling javascript-functions as in the test-scenario above worked in previous versions of WinDbg.

    ++++ Questions ++++
    1) Can you reproduce this issue on your site ?
    2) Is it legal to use javascript-functions in this way ?
    Your feedback is greatly appreciated! (I posted this issue to but did not get a feedback.)

    Kind/Best regards,

  • User profile image

    @dbgeek: To make sure the debugger team gets this and can track it appropriately, it's probably best to submit this report via the Feedback Hub from WinDbg Preview.

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