Fix unwinding of partial stack traces.

- Architecture::CreateStackTrace() now uses the last frame's
  PreviousCpuState() as the basis to continue unwinding when passed
  a partial trace to continue from, rather than the (incorrect) actual
  cpu state of that frame, which would have resulted in the last frame
  being duplicated in the trace.

- Renamed variables to be more clear.

src/apps/debugger/arch/Architecture.cpp

@@ -100,7 +100,7 @@ Architecture::CreateStackTrace(Team* team,
 
 	StackTrace* stackTrace = NULL;
 	ObjectDeleter<StackTrace> stackTraceDeleter;
-	StackFrame* frame = NULL;
+	StackFrame* nextFrame = NULL;
 
 	if (useExistingTrace)
 		stackTrace = _stackTrace;
@@ -115,8 +115,8 @@ Architecture::CreateStackTrace(Team* team,
 	// if we're passed an already existing partial stack trace,
 	// attempt to continue building it from where it left off.
 	if (stackTrace->CountFrames() > 0) {
-		frame = stackTrace->FrameAt(stackTrace->CountFrames() - 1);
-		cpuState = frame->GetCpuState();
+		nextFrame = stackTrace->FrameAt(stackTrace->CountFrames() - 1);
+		cpuState = nextFrame->GetPreviousCpuState();
 	}
 
 	while (cpuState != NULL) {
@@ -152,42 +152,42 @@ Architecture::CreateStackTrace(Team* team,
 
 		// If the CPU state's instruction pointer is actually the return address
 		// of the next frame, we let the architecture fix that.
-		if (frame != NULL
-			&& frame->ReturnAddress() == cpuState->InstructionPointer()) {
-			UpdateStackFrameCpuState(frame, image,
+		if (nextFrame != NULL
+			&& nextFrame->ReturnAddress() == cpuState->InstructionPointer()) {
+			UpdateStackFrameCpuState(nextFrame, image,
 				functionDebugInfo, cpuState);
 		}
 
 		// create the frame using the debug info
-		StackFrame* previousFrame = NULL;
+		StackFrame* frame = NULL;
 		CpuState* previousCpuState = NULL;
 		if (function != NULL) {
 			status_t error = functionDebugInfo->GetSpecificImageDebugInfo()
-				->CreateFrame(image, function, cpuState, previousFrame,
+				->CreateFrame(image, function, cpuState, frame,
 					previousCpuState);
 			if (error != B_OK && error != B_UNSUPPORTED)
 				break;
 		}
 
 		// If we have no frame yet, let the architecture create it.
-		if (previousFrame == NULL) {
+		if (frame == NULL) {
 			status_t error = CreateStackFrame(image, functionDebugInfo,
-				cpuState, frame == NULL, previousFrame, previousCpuState);
+				cpuState, nextFrame == NULL, frame, previousCpuState);
 			if (error != B_OK)
 				break;
 		}
 
 		cpuStateReference.SetTo(previousCpuState, true);
 
-		previousFrame->SetImage(image);
-		previousFrame->SetFunction(function);
+		frame->SetImage(image);
+		frame->SetFunction(function);
 
-		if (!stackTrace->AddFrame(previousFrame)) {
-			delete previousFrame;
+		if (!stackTrace->AddFrame(frame)) {
+			delete frame;
 			return B_NO_MEMORY;
 		}
 
-		frame = previousFrame;
+		frame = nextFrame;
 		cpuState = previousCpuState;
 		if (--maxStackDepth == 0)
 			break;

src/apps/debugger/arch/Architecture.h

@@ -67,7 +67,7 @@ public:
 	virtual	status_t			CreateStackFrame(Image* image,
 									FunctionDebugInfo* function,
 									CpuState* cpuState, bool isTopFrame,
-									StackFrame*& _previousFrame,
+									StackFrame*& _frame,
 									CpuState*& _previousCpuState) = 0;
 										// returns reference to previous frame
 										// and CPU state; returned CPU state

src/apps/debugger/arch/x86/ArchitectureX86.cpp

@@ -265,7 +265,7 @@ ArchitectureX86::CreateCpuState(const void* cpuStateData, size_t size,
 
 status_t
 ArchitectureX86::CreateStackFrame(Image* image, FunctionDebugInfo* function,
-	CpuState* _cpuState, bool isTopFrame, StackFrame*& _previousFrame,
+	CpuState* _cpuState, bool isTopFrame, StackFrame*& _frame,
 	CpuState*& _previousCpuState)
 {
 	CpuStateX86* cpuState = dynamic_cast<CpuStateX86*>(_cpuState);
@@ -382,11 +382,12 @@ ArchitectureX86::CreateStackFrame(Image* image, FunctionDebugInfo* function,
 		previousCpuState->SetIntRegister(X86_REGISTER_EBP,
 			previousFramePointer);
 		previousCpuState->SetIntRegister(X86_REGISTER_EIP, returnAddress);
+		frame->SetPreviousCpuState(previousCpuState);
 	}
 
 	frame->SetReturnAddress(returnAddress);
 
-	_previousFrame = frameReference.Detach();
+	_frame = frameReference.Detach();
 	_previousCpuState = previousCpuState;
 	return B_OK;
 }

src/apps/debugger/debug_info/DwarfImageDebugInfo.cpp

@@ -495,7 +495,7 @@ DwarfImageDebugInfo::GetAddressSectionType(target_addr_t address)
 status_t
 DwarfImageDebugInfo::CreateFrame(Image* image,
 	FunctionInstance* functionInstance, CpuState* cpuState,
-	StackFrame*& _previousFrame, CpuState*& _previousCpuState)
+	StackFrame*& _frame, CpuState*& _previousCpuState)
 {
 	DwarfFunctionDebugInfo* function = dynamic_cast<DwarfFunctionDebugInfo*>(
 		functionInstance->GetFunctionDebugInfo());
@@ -634,9 +634,11 @@ DwarfImageDebugInfo::CreateFrame(Image* image,
 		instructionPointer, functionInstance->Address() - fRelocationDelta,
 		subprogramEntry->Variables(), subprogramEntry->Blocks());
 
-	_previousFrame = frameReference.Detach();
+	_frame = frameReference.Detach();
 	_previousCpuState = previousCpuStateReference.Detach();
 
+	frame->SetPreviousCpuState(_previousCpuState);
+
 	return B_OK;
 }
 

src/apps/debugger/debug_info/DwarfImageDebugInfo.h

@@ -61,7 +61,7 @@ public:
 	virtual	status_t			CreateFrame(Image* image,
 									FunctionInstance* functionInstance,
 									CpuState* cpuState,
-									StackFrame*& _previousFrame,
+									StackFrame*& _frame,
 									CpuState*& _previousCpuState);
 	virtual	status_t			GetStatement(FunctionDebugInfo* function,
 									target_addr_t address,

src/apps/debugger/debug_info/SpecificImageDebugInfo.h

@@ -53,7 +53,7 @@ public:
 	virtual	status_t			CreateFrame(Image* image,
 									FunctionInstance* functionInstance,
 									CpuState* cpuState,
-									StackFrame*& _previousFrame,
+									StackFrame*& _Frame,
 									CpuState*& _previousCpuState) = 0;
 										// returns reference to previous frame
 										// and CPU state; returned CPU state