SCI: Stop getCurrentCallOrigin from mutating stack frames

This fixes incorrect backtraces after a workaround failure or
other call to getCurrentCallOrigin when one or more stack frames
are calls to local procedures.

2 files changed, 11 insertions, 8 deletions

diff --git a/engines/sci/engine/state.cpp b/engines/sci/engine/state.cpp
index c23add1211..76df322b30 100644
--- a/engines/sci/engine/state.cpp
+++ b/engines/sci/engine/state.cpp
@@ -390,26 +390,29 @@ SciCallOrigin EngineState::getCurrentCallOrigin() const {
 	const Script *localScript = _segMan->getScriptIfLoaded(xs->local_segment);
 	int curScriptNr = localScript->getScriptNumber();
 
+	Selector debugSelector = xs->debugSelector;
+	int debugExportId = xs->debugExportId;
+
 	if (xs->debugLocalCallOffset != -1) {
 		// if lastcall was actually a local call search back for a real call
 		Common::List<ExecStack>::const_iterator callIterator = _executionStack.end();
 		while (callIterator != _executionStack.begin()) {
 			callIterator--;
 			const ExecStack &loopCall = *callIterator;
-			if ((loopCall.debugSelector != -1) || (loopCall.debugExportId != -1)) {
-				xs->debugSelector = loopCall.debugSelector;
-				xs->debugExportId = loopCall.debugExportId;
+			if (loopCall.debugSelector != -1 || loopCall.debugExportId != -1) {
+				debugSelector = loopCall.debugSelector;
+				debugExportId = loopCall.debugExportId;
 				break;
 			}
 		}
 	}
 
 	if (xs->type == EXEC_STACK_TYPE_CALL) {
-		if (xs->debugSelector != -1) {
-			curMethodName = g_sci->getKernel()->getSelectorName(xs->debugSelector);
-		} else if (xs->debugExportId != -1) {
+		if (debugSelector != -1) {
+			curMethodName = g_sci->getKernel()->getSelectorName(debugSelector);
+		} else if (debugExportId != -1) {
 			curObjectName = "";
-			curMethodName = Common::String::format("export %d", xs->debugExportId);
+			curMethodName = Common::String::format("export %d", debugExportId);
 		}
 	}
 
diff --git a/engines/sci/engine/workarounds.cpp b/engines/sci/engine/workarounds.cpp
index 148e9e77c3..025e94ad76 100644
--- a/engines/sci/engine/workarounds.cpp
+++ b/engines/sci/engine/workarounds.cpp
@@ -876,7 +876,7 @@ const SciWorkaroundEntry kScrollWindowAdd_workarounds[] = {
 
 SciWorkaroundSolution trackOriginAndFindWorkaround(int index, const SciWorkaroundEntry *workaroundList, SciCallOrigin *trackOrigin) {
 	const EngineState *state = g_sci->getEngineState();
-	ExecStack *lastCall = state->xs;
+	const ExecStack *lastCall = state->xs;
 	const SciGameId gameId = g_sci->getGameId();
 
 	*trackOrigin = state->getCurrentCallOrigin();