[PATCH] trace-cruncher: Fix default function arguments in utils

[PATCH] trace-cruncher: Fix default function arguments in utils

[Yordan Karadzhov (VMware)]

In Python the argument defaults are set when the function is defined.
Using mutable types as default values will set the desired value only
the first time the function is called.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 tracecruncher/ft_utils.py | 50 +++++++++++++++++++++++++++++----------
 1 file changed, 37 insertions(+), 13 deletions(-)

diff --git a/tracecruncher/ft_utils.py b/tracecruncher/ft_utils.py
index b27f38a..f0bed95 100644
--- a/tracecruncher/ft_utils.py
+++ b/tracecruncher/ft_utils.py
@@ -115,21 +115,24 @@ class tc_kprobe(_kprobe_base):
         self.register()
 
 
-def kprobe_add_raw_field(name, probe, fields={}):
+def kprobe_add_raw_field(name, probe, fields=None):
     """ Add a raw definition of a data field to the probe descriptor.
     """
+    if fields is None:
+        fields = {}
+
     fields[str(name)] = str(probe)
     return fields
 
 
-def kprobe_add_arg(name, param_id, param_type, fields={}):
+def kprobe_add_arg(name, param_id, param_type, fields=None):
     """ Add a function parameter data field to the probe descriptor.
     """
     probe = '$arg{0}:{1}'.format(param_id, param_type)
     return kprobe_add_raw_field(name=name, probe=probe, fields=fields)
 
 
-def kprobe_add_ptr_arg(name, param_id, param_type, offset=0, fields={}):
+def kprobe_add_ptr_arg(name, param_id, param_type, offset=0, fields=None):
     """ Add a pointer function parameter data field to the probe descriptor.
     """
     probe = '+{0}($arg{1}):{2}'.format(offset, param_id, param_type)
@@ -137,7 +140,7 @@ def kprobe_add_ptr_arg(name, param_id, param_type, offset=0, fields={}):
 
 
 def kprobe_add_array_arg(name, param_id, param_type, offset=0,
-                         size=-1, fields={}):
+                         size=-1, fields=None):
     """ Add an array function parameter data field to the probe descriptor.
     """
     if size < 0:
@@ -151,7 +154,7 @@ def kprobe_add_array_arg(name, param_id, param_type, offset=0,
         return kprobe_add_raw_field(name=field_name, probe=probe, fields=fields)
 
 
-def kprobe_add_string_arg(name, param_id, offset=0, usr_space=False, fields={}):
+def kprobe_add_string_arg(name, param_id, offset=0, usr_space=False, fields=None):
     """ Add a string function parameter data field to the probe descriptor.
     """
     p_type = 'ustring' if usr_space else 'string'
@@ -163,7 +166,7 @@ def kprobe_add_string_arg(name, param_id, offset=0, usr_space=False, fields={}):
 
 
 def kprobe_add_string_array_arg(name, param_id, offset=0, usr_space=False,
-                                size=-1, fields={}):
+                                size=-1, fields=None):
     """ Add a string array function parameter data field to the probe descriptor.
     """
     p_type = 'ustring' if usr_space else 'string'
@@ -216,14 +219,14 @@ class tc_eprobe(_dynevent):
         self.register()
 
 
-def eprobe_add_ptr_field(name, target_field, field_type, offset=0, fields={}):
+def eprobe_add_ptr_field(name, target_field, field_type, offset=0, fields=None):
     """ Add a pointer data field to the eprobe descriptor.
     """
     probe = '+{0}(${1}):{2}'.format(offset, target_field, field_type)
     return kprobe_add_raw_field(name=name, probe=probe, fields=fields)
 
 
-def eprobe_add_string_field(name, target_field, offset=0, usr_space=False, fields={}):
+def eprobe_add_string_field(name, target_field, offset=0, usr_space=False, fields=None):
     """ Add a string data field to the eprobe descriptor.
     """
     f_type = 'ustring' if usr_space else 'string'
@@ -235,8 +238,8 @@ def eprobe_add_string_field(name, target_field, offset=0, usr_space=False, field
 
 
 class tc_hist:
-    def __init__(self, name, event, axes, weights=[],
-                 sort_keys=[], sort_dir={}, find=False):
+    def __init__(self, name, event, axes, weights,
+                 sort_keys, sort_dir, find=False):
         """ Constructor.
         """
         self.name = name
@@ -330,9 +333,18 @@ class tc_hist:
         return self.data()
 
 
-def create_hist(name, event, axes, weights=[], sort_keys=[], sort_dir={}):
+def create_hist(name, event, axes, weights=None, sort_keys=None, sort_dir=None):
     """ Create new kernel histogram.
     """
+    if weights is None:
+        weights = []
+
+    if sort_keys is None:
+        sort_keys = []
+
+    if sort_dir is None:
+        sort_dir = {}
+
     try:
         hist = tc_hist(name=name, event=event, axes=axes, weights=weights,
                        sort_keys=sort_keys, sort_dir=sort_dir, find=False)
@@ -343,9 +355,18 @@ def create_hist(name, event, axes, weights=[], sort_keys=[], sort_dir={}):
     return hist
 
 
-def find_hist(name, event, axes, weights=[], sort_keys=[], sort_dir={}):
+def find_hist(name, event, axes, weights=None, sort_keys=None, sort_dir=None):
     """ Find existing kernel histogram.
     """
+    if weights is None:
+        weights = []
+
+    if sort_keys is None:
+        sort_keys = []
+
+    if sort_dir is None:
+        sort_dir = {}
+
     try:
         hist = tc_hist(name=name, event=event, axes=axes, weights=weights,
                        sort_keys=sort_keys, sort_dir=sort_dir, find=True)
@@ -432,10 +453,13 @@ class tc_synth(tc_event):
         return self.synth.repr(event=True, hist_start=True, hist_end=True)
 
 
-def synth_event_item(event, match, fields=[]):
+def synth_event_item(event, match, fields=None):
     """ Create descriptor for an event item (component) of a synthetic event.
         To be used as a start/end event.
     """
+    if fields is None:
+        fields = []
+
     sub_evt = {}
     sub_evt['event'] = event
     sub_evt['fields'] = fields
-- 
2.32.0