Microsoft KB Archive/105275

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Using the "BR" Command in WDEB386.EXE

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Q105275

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

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SUMMARY
The "BR" command in WDEB386.EXE uses the debug registers of the Intel 386 and above processors to break into the debugger on memory accesses. These accesses can be in byte, word, or dword sizes involving a read, write, or execute instruction. Because the BR command is very specific as to the type of memory access it will trap, care must be taken to choose the correct combination of BR settings in order to obtain all possible cases:

  E == execute access W == write access R == read access

1 == byte sized access 2 == word sized access 4 == dword sized access When a break into the debugger is required when a memory location is modified, set a few BR breakpoints on a Write operation giving the three different operand sizes:

BR W1 seg:off

BR W2 seg:off

BR W4 seg:off This should cover all possible cases of the memory being touched.

Additional query words: 3.10 no32bit 3.00 breakpoint br

Keywords : kb16bitonly

Issue type :

Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310