Fix debugger for flat PC and non-flat frame.

dlls/dbghelp/stack.c

@@ -113,6 +113,13 @@ BOOL WINAPI StackWalk(DWORD MachineType, HANDLE hProcess, HANDLE hThread,
     {
         THREAD_BASIC_INFORMATION info;
 
+        if ((frame->AddrPC.Mode == AddrModeFlat) &&
+            (frame->AddrFrame.Mode != AddrModeFlat))
+        {
+            WARN("Bad AddrPC.Mode / AddrFrame.Mode combination\n");
+            goto done_err;
+        }
+
         /* Init done */
         curr_mode = (frame->AddrPC.Mode == AddrModeFlat) ? 
             stm_32bit : stm_16bit;

programs/winedbg/stack.c

@@ -188,6 +188,13 @@ void stack_backtrace(DWORD tid, BOOL noisy)
     memory_get_current_frame(&sf.AddrFrame);
     memory_get_current_pc(&sf.AddrPC);
 
+    /* don't confuse StackWalk by passing in inconsistent addresses */
+    if ((sf.AddrPC.Mode == AddrModeFlat) && (sf.AddrFrame.Mode != AddrModeFlat))
+    {
+        sf.AddrFrame.Offset = (DWORD)memory_to_linear_addr(&sf.AddrFrame);
+        sf.AddrFrame.Mode = AddrModeFlat;
+    }
+
     if (noisy) dbg_printf("Backtrace:\n");
     while (StackWalk(IMAGE_FILE_MACHINE_I386, dbg_curr_process->handle, 
                      thread->handle, &sf, &dbg_context, NULL, SymFunctionTableAccess,