[lldb/crashlog] Fix exception signal parsing

[mib]

Summary

In some cases, it can happen that crashlogs don't have any signal in
the exception, which causes the parser to crash.

This fixes the parsing by checking if the signal field is in the
exception dictionary before trying to access it.

Signed-off-by: Med Ismail Bennani <[e-mail]>

[JDevlieghere]

lldb/examples/python/crashlog.py

471

Should this be surrounded by spaces?

[mib]

lldb/examples/python/crashlog.py

476

@JDevlieghere Here it's only prepended by a space, which is honored in my change since I concatenate "({})".format(json_exception['signal']) to exception_signal (which is initialized with a space).

I don't think this should have a trailing space because it's not guaranteed that we get something in exception_extra.

[JDevlieghere]

LGTM

lldb/examples/python/crashlog.py

476

Thanks, I missed the + in +=, I thought it was just an assignment.

lldb/examples/python/crashlog.py

class JSONCrashLogParser:
 
     def parse_process_info(self, json_data):
         self.crashlog.process_id = json_data['pid']
         self.crashlog.process_identifier = json_data['procName']
         self.crashlog.process_path = json_data['procPath']
 
     def parse_crash_reason(self, json_exception):
         exception_type = json_exception['type']
-        exception_signal = json_exception['signal']
+        exception_signal = " "
+        if 'signal' in json_exception:
+            exception_signal += "({})".format(json_exception['signal'])
+
         if 'codes' in json_exception:
             exception_extra = " ({})".format(json_exception['codes'])
         elif 'subtype' in json_exception:
             exception_extra = " ({})".format(json_exception['subtype'])
         else:
             exception_extra = ""
-        return "{} ({}){}".format(exception_type, exception_signal,
+        return "{}{}{}".format(exception_type, exception_signal,
                                   exception_extra)
 
     def parse_images(self, json_images):
         idx = 0
         for json_image in json_images:
             img_uuid = uuid.UUID(json_image['uuid'])
             low = int(json_image['base'])
             high = int(0)