Using Debugging Support

The following example uses the WaitForDebugEvent and ContinueDebugEvent functions to illustrate how a simple debugger might be organized.

DEBUG_EVENT DebugEv; // debugging event information

DWORD dwContinueStatus = DBG_CONTINUE; // exception continuation

for(;;)

{

// Wait for a debugging event to occur. The second parameter indicates

// that the function does not return until a debugging event occurs.

WaitForDebugEvent(&DebugEv, INFINITE);

// Process the debugging event code.

switch (DebugEv.dwDebugEventCode)

{

case EXCEPTION_DEBUG_EVENT:

// Process the exception code. When handling

// exceptions, remember to set the continuation

// status parameter (dwContinueStatus). This value

// is used by the ContinueDebugEvent function.

switch (DebugEv.u.Exception.ExceptionRecord.ExceptionCode)

{

case EXCEPTION_ACCESS_VIOLATION:

// First chance: Pass this on to the kernel.

// Last chance: Display an appropriate error.

case EXCEPTION_BREAKPOINT:

// First chance: Display the current

// instruction and register values.

case EXCEPTION_DATATYPE_MISALIGNMENT:

// First chance: Pass this on to the kernel.

// Last chance: Display an appropriate error.

case EXCEPTION_SINGLE_STEP:

// First chance: Update the display of the

// current instruction and register values.

case DBG_CONTROL_C:

// First chance: Pass this on to the kernel.

// Last chance: Display an appropriate error.

// Handle other exceptions.

}

case CREATE_THREAD_DEBUG_EVENT:

// As needed, examine or change the thread's registers

// with the GetThreadContext and SetThreadContext functions;

// and suspend and resume thread execution with the

// SuspendThread and ResumeThread functions.

case CREATE_PROCESS_DEBUG_EVENT:

// As needed, examine or change the registers of the

// process's initial thread with the GetThreadContext and

// SetThreadContext functions; read from and write to the

// process's virtual memory with the ReadProcessMemory and

// WriteProcessMemory functions; and suspend and resume

// thread execution with the SuspendThread and ResumeThread

// functions.

case EXIT_THREAD_DEBUG_EVENT:

// Display the thread's exit code.

case EXIT_PROCESS_DEBUG_EVENT:

// Display the process's exit code.

case LOAD_DLL_DEBUG_EVENT:

// Read the debugging information included in the newly

// loaded DLL.

case UNLOAD_DLL_DEBUG_EVENT:

// Display a message that the DLL has been unloaded.

case OUTPUT_DEBUG_STRING_EVENT:

// Display the output debugging string.

}

// Resume executing the thread that reported the debugging event.

ContinueDebugEvent(DebugEv.dwProcessId,

DebugEv.dwThreadId, dwContinueStatus);

}

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