Winmerge plugin

Author: David Zimmer
Date: 01.24.14 - 6:18am

I got thinking a little more about using the winmerge plugin for disasm diffing again last night and had a few simple ideas that panned out really well.

So I was aggressively cutting the asm down to just the base instruction, order, and any new lines from where labels were. With an extra 5 minutes of coding I was able to get the match with a less aggressive filter. The full logic is:
If InStr(tmp(i), "[") > 0 Then baseCmd = baseCmd & "[]"
If InStr(tmp(i), "+") > 0 Then baseCmd = baseCmd & "+"
If InStr(tmp(i), "-") > 0 Then baseCmd = baseCmd & "-"
If InStr(tmp(i), "*") > 0 Then baseCmd = baseCmd & "*"
If ExtractConstant(tmp(i), x) Then baseCmd = baseCmd & x
Ridiculously simple, but leaves enough information in for diffutils to work much better. I also added in a slightly more complex parser as well that standardizes the asm back closer to the generic assembler mnemonics for the instructions (eg reg32, reg16 etc). Both are included in the latest build. It is interesting to test how simple is sufficient. (anyone can make a complex system, elegance is in simplicity)

I also had another idea. I wanted two more things out of my Winmerge plugin. I wanted it to be able to house multiple filters, configurable externally, and I wanted it to contain a debug interface where you could watch the data transformations and edit them manually if need be.

Both of these were also really easily added. The filter selection is based on a registry key setting set in IDACompare, and for the debug UI, All i had to do is show a form modally which pauses WinMerge and displays the data letting the user view/edit the data in real time.

When they hit continue, it goes back and WinMerge continues. Super slick.

I love that WinMerge used COM for its plugins. Below is a screen shot of the debug UI showing the signature based standardization.

(click for larger image)

The resulting diff below shows the same problem section from the last post now showing the correct results.

(click for larger image)

Sometimes its amazing what 5 minutes of coding can do :)

Comments: (1)

On 01.27.14 - 12:36am Dave wrote:
Even there there is no way to automatically configure WinMerge to apply the prediffer automatically, It turned out to be pretty easy to do it externally.
AppActivate "WinMerge - [a.idacompare - b.idacompare]"
SendKeys "%p"       //send alt-p to select plugin menu
SendKeys "{DOWN 4}" //down arrow 4x
SendKeys "{RIGHT}"  //right arrow 1x
SendKeys "{DOWN 2}" //down arrow 2x
SendKeys vbCr       //enter

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