How do I access an array when pretty printing in gdb? - gdb

Question

I'm able to get the value using ptr.dereference, however I have no idea how to increment the pointer to get the next value. Assume I'm using a 16bit signed array. How do I get the first 5 values?
class MyArrayPrinter:
"Print a MyArray"
def __init__ (self, val):
self.val = val
def to_string (self):
return "Array of"
def children(self):
ptr = self.val['array']
#yield ('0', ptr.address[1].dereference())
yield ('5', 47)
def display_hint (self):
return 'array'

Answer 1

For this simple array class, taken from your other question:
template<class T>
struct MyArray
{
int pos;
T array[10];
MyArray() : pos(0) {}
void push(T val) {
if (pos >= 10)
return;
array[pos++] = val;
}
};
I would implement the pretty printer like this:
class MyArrayPrinter:
"Print a MyArray"
class _iterator:
def __init__ (self, start, finish):
self.item = start
self.finish = finish
self.count = 0
def __iter__ (self):
return self
def __next__ (self):
count = self.count
self.count = self.count + 1
if self.item == self.finish:
raise StopIteration
elt = self.item.dereference()
self.item = self.item + 1
return ('[%d]' % count, elt)
def next (self):
return self.__next__()
def __init__ (self, val):
self.val = val
def children (self):
start = self.val['array'][0].address
return self._iterator(start, start + self.val['pos'])
def to_string (self):
len = self.val['pos']
return '%s of length %d' % (self.val.type, len)
def display_hint (self):
return 'array'
pp = gdb.printing.RegexpCollectionPrettyPrinter("mine")
pp.add_printer('MyArray', '^MyArray<.*>$', MyArrayPrinter)
gdb.printing.register_pretty_printer(gdb.current_objfile(), pp)
Which would look like this:
(gdb) p arr
$1 = MyArray<MyString> of length 2 = {"My test string", "has two"}
(gdb) p arr2
$2 = MyArray<MoreComplex*> of length 1 = {0x22fe00}