[lldb/crashlog] Fix line entries resolution in interactive mode

This patch subtracts 1 to the pc of any frame above frame 0 to get the
previous line entry and display the right line in the debugger.

This also rephrase some old comment from `48d157dd4`.

rdar://92686666

Differential Revision: https://reviews.llvm.org/D125928

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

lldb/examples/python/crashlog.py

@@ -115,8 +115,8 @@ class CrashLog(symbolication.Symbolicator):
                 disassemble = (
                     this_thread_crashed or options.disassemble_all_threads) and frame_idx < options.disassemble_depth
 
-                # Any frame above frame zero and we have to subtract one to
-                # get the previous line entry.
+                # Except for the zeroth frame, we should subtract 1 from every
+                # frame pc to get the previous line entry.
                 pc = frame.pc & crash_log.addr_mask
                 pc = pc if frame_idx == 0 or pc == 0 else pc - 1
                 symbolicated_frame_addresses = crash_log.symbolicate(pc, options.verbose)

lldb/examples/python/scripted_process/crashlog_scripted_process.py

@@ -16,6 +16,7 @@ class CrashLogScriptedProcess(ScriptedProcess):
             return
 
         self.pid = crash_log.process_id
+        self.addr_mask = crash_log.addr_mask
         self.crashed_thread_idx = crash_log.crashed_thread_idx
         self.loaded_images = []
 
@@ -122,11 +123,13 @@ class CrashLogScriptedThread(ScriptedThread):
             return None
 
         for frame in self.backing_thread.frames:
+            frame_pc = frame.pc & self.scripted_process.addr_mask
+            pc = frame_pc if frame.index == 0  or frame_pc == 0 else frame_pc - 1
             sym_addr = lldb.SBAddress()
-            sym_addr.SetLoadAddress(frame.pc, self.target)
+            sym_addr.SetLoadAddress(pc, self.target)
             if not sym_addr.IsValid():
                 continue
-            self.frames.append({"idx": frame.index, "pc": frame.pc})
+            self.frames.append({"idx": frame.index, "pc": pc})
 
         return self.frames