More documentation changes (WIP)
git-svn-id: https://llvm.org/svn/llvm-project/llvdb/trunk@138421 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/examples/synthetic/StdVectorSynthProvider.py b/examples/synthetic/StdVectorSynthProvider.py
index 2730498..a69ab29 100644
--- a/examples/synthetic/StdVectorSynthProvider.py
+++ b/examples/synthetic/StdVectorSynthProvider.py
@@ -2,19 +2,20 @@
def __init__(self, valobj, dict):
self.valobj = valobj;
- self.update()
+ self.update() # initialize this provider
def num_children(self):
- start_val = self.start.GetValueAsUnsigned(0)
- finish_val = self.finish.GetValueAsUnsigned(0)
- end_val = self.end.GetValueAsUnsigned(0)
+ start_val = self.start.GetValueAsUnsigned(0) # read _M_start
+ finish_val = self.finish.GetValueAsUnsigned(0) # read _M_finish
+ end_val = self.end.GetValueAsUnsigned(0) # read _M_end_of_storage
+
# Before a vector has been constructed, it will contain bad values
# so we really need to be careful about the length we return since
# unitialized data can cause us to return a huge number. We need
# to also check for any of the start, finish or end of storage values
# being zero (NULL). If any are, then this vector has not been
# initialized yet and we should return zero
-
+
# Make sure nothing is NULL
if start_val == 0 or finish_val == 0 or end_val == 0:
return 0
@@ -25,23 +26,46 @@
if finish_val > end_val:
return 0
+ # pointer arithmetic: (_M_finish - _M_start) would return the number of
+ # items of type T contained in the vector. because Python has no way to know
+ # that we want to subtract two pointers instead of two integers, we have to divide
+ # by sizeof(T) to be equivalent to the C++ pointer expression
num_children = (finish_val-start_val)/self.data_size
return num_children
+ # we assume we are getting children named [0] thru [N-1]
+ # if for some reason our child name is not in this format,
+ # do not bother to show it, and return an invalid value
def get_child_index(self,name):
- return int(name.lstrip('[').rstrip(']'))
+ try:
+ return int(name.lstrip('[').rstrip(']'))
+ except:
+ return -1;
def get_child_at_index(self,index):
+ # LLDB itself should never query for children < 0, but this might come
+ # from someone asking for a nonexisting child and getting -1 as index
+ if index < 0:
+ return None
if index >= self.num_children():
return None;
- offset = index * self.data_size
- return self.start.CreateChildAtOffset('['+str(index)+']',offset,self.data_type)
+ # *(_M_start + index), or equivalently _M_start[index] is C++ code to
+ # read the index-th item of the vector. in Python we must make an offset
+ # that is index * sizeof(T), and then grab the value at that offset from
+ # _M_start
+ offset = index * self.data_size # index * sizeof(T)
+ return self.start.CreateChildAtOffset('['+str(index)+']',offset,self.data_type) # *(_M_start + index)
+ # an std::vector contains an object named _M_impl, which in turn contains
+ # three pointers, _M_start, _M_end and _M_end_of_storage. _M_start points to the
+ # beginning of the data area, _M_finish points to where the current vector elements
+ # finish, and _M_end_of_storage is the end of the currently alloc'ed memory portion
+ # (to allow resizing, a vector may allocate more memory than required)
def update(self):
impl = self.valobj.GetChildMemberWithName('_M_impl')
self.start = impl.GetChildMemberWithName('_M_start')
self.finish = impl.GetChildMemberWithName('_M_finish')
self.end = impl.GetChildMemberWithName('_M_end_of_storage')
- self.data_type = self.start.GetType().GetPointeeType()
- self.data_size = self.data_type.GetByteSize()
+ self.data_type = self.start.GetType().GetPointeeType() # _M_start is defined as a T*
+ self.data_size = self.data_type.GetByteSize() # sizeof(T)