Little Known VC++ Debugging Tricks

Little Known Native Debugging Tricks Ofek Shilon Algorithms Team Leader @ Sarin Technologies www.thetweaker.wordpress.com

DISCLAIMER

VS AS AN INTERPRETER

Expression Evaluator
Scope
Watch, QuickWatch,
Immediate,
BP conditions, ‘when hit’
Call Functions from the debugger!
Demo

Context Operator
Documentation is wrong.
VS2010 blocked WIN-API, but eased usage of others.
Thread context
Access insensitive
Blind to inlined functions

Things to try:
Very explicit casting,
Explicit addresses.

Edit and Continue
Demo
Stale code

Edit and Continue
Preparation: /ZI, /INCREMENTAL

Edit and Continue
Limitations:
Inconsistent with /RELEASE, /OPT:REF, /OPT:ICF, /ORDER, /FORCE,
Does not invoke custom build steps,
Isn’t supported on attached processes,
Can’t change object layout,
Doesn’t regenerate IDL files,
Can’t change resource files,
Does not build static libs.

CLICK SAVERS

StepOver
Demo

StepOver
VC6: autoexp section [ExecutionControl]
VC7: Reg key - HKCUSoftwareMicrosoftVisualStudio7.0NativeDEStepOver
VC8: HK LM SoftwareMicrosoftVisualStudio8.0NativeDEStepOver
VC10: HK CU SoftwareMicrosoftVisualStudio10.0 _Config NativeDEStepOver Dropped ‘=NoStepInto’ syntax

StepOver
Warning!
When 2 or more instances of VS2010 are active, occasionally it would create and use a duplicate reg key: HKCUSoftwareMicrosoftVisualStudio10.0_Config_%PID% (e.g., …VisualStudio10.0_Config_6172) … and all ’10.0_Config’ modifications would have no effect !
Credit: Andy Pennell http://blogs.msdn.com/b/andypennell/archive/2004/02/06/69004.aspx

autoexp
How’s the debugger ‘aware’ of STL containers?
autoexp.dat
By default at %VS folder %Common7PackagesDebugger
Provide alternate path in environment variable: _vcee_autoexp

autoexp
Demo
Specialized syntax for common containers: Array, List, Map, Tree.
Re-parsed on every debugging session
Extremely fragile, yet excellent investment

autoexp
Status limbo:

autoexp
Bypass locally: xxx ,!
Bypass globally in Tools/Options:

autoexp
Resources:
Avery Lee http://virtualdub.org/blog/pivot/entry.php?id=120
Stephan T. Lavavej BoostCon presentation http://filetolink.com/d/? h=a456fc7fd3d35644edcbe5e764d1ba63&t=1315076450&f=17ad36ef
My blog: complete MFC containers visualization, Matrix 2D visualization.. www.thetweaker.wordpress.org

Sound Alerts
Win7: Control Panel Hardware and Sounds Sound Change system sounds
WinXP: Control Panel Sounds and Audio... Program Events – Microsoft Developer

TRACING ERRORS

GetLastError Interactively
GetLastError implementation:
(int*)($fs)+0x34
(int*)($tib)+0x34
$err !
Credit: msdn http:// msdn.microsoft.com/en-us/library/dtw169z6.aspx

Extensions
Customizing ‘,hr’ display in autoexp.dat:
Other TEB data: (_TEB*)$tib

Breaking on Errors
BP location: (int*)($tib)+0x34
Specific error: BP condition
Slooooooooow
g_dwLastErrorToBreakOn !
(int*){,,ntdll.dll}_g_dwLastErrorToBreakOn
Seems to fail for Win7.
Credit: Daniel Pearson, http:// blogs.msdn.com/b/danpear/archive/2007/04/06/2033100.aspx

INVESTIGATING CODE

Breaking on all class methods
Break at function: Class::*
Credit: Habib Heydarian http :// blogs.msdn.com/b/habibh/archive/2009/09/10/class-breakpoint-how-to-set-a-breakpoint-on-a-c-class-in-the-visual-studio-debugger.aspx

Naming Native Threads
Demo
‘ Documented hack’ Credit: MSDN http:// msdn.microsoft.com/en-us/library/xcb2z8hs.aspx

Breaking on Data Read
Write-to BPs are implemented in hardware – dedicated x86 debug registers.
Read-from debugs registers are available too, but were never exposed in VS.
Some code required to set the register values to the desired address.
Links to 4 implementations: http://thetweaker.wordpress.com/2011/05/22/breaking-on-data-read /

Breaking on Data Read
Usage:
Interactive:

Static Object Layout
/d1reportSingleClassLayout
/d1reportAllClassLayout
Credit: Andy Rich http:// blogs.msdn.com/b/vcblog/archive/2007/05/17/diagnosing-hidden-odr-violations-in-visual-c-and-fixing-lnk2022.aspx

ENHANCED DIAGNOSIS

Useful Pseudo-registers
$tid -> very useful as a BP condition.
$env=0 -> view debugee environment variables
$cmdline = 0 -> view launching command line

Useful Pseudo-registers
$handles -> narrows down handle leaks
$clk -> rough profiling
$user -> view permissions info
Credits: Steve Steiner, Gregg Miskelly, et. al. http ://blogs.msdn.com/b/stevejs / http://blogs.msdn.com/b/greggm /

Searching Through Memory
Credit: msdn http:// msdn.microsoft.com/en-us/library/ms171363.aspx

THANK YOU. www.thetweaker.wordpress.com [email_address]

Little Known VC++ Debugging Tricks

by Ofek Shilon on Sep 08, 2011

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