gdb/libpython.py: Update PyLongObjectPtr docstring (pythonGH-118438)

Tools/gdb/libpython.py

@@ -255,7 +255,7 @@ def proxyval(self, visited):
 
  Derived classes will override this.
 
- For example, a PyIntObject* with ob_ival 42 in the inferior process
+ For example, a PyLongObjectPtr* with long_value 42 in the inferior process
  should result in an int(42) in this process.
 
  visited: a set of all gdb.Value pyobject pointers already visited
@@ -867,7 +867,7 @@ class PyLongObjectPtr(PyObjectPtr):
 
  def proxyval(self, visited):
  '''
- Python's Include/longobjrep.h has this declaration:
+ Python's Include/longinterpr.h has this declaration:
 
  typedef struct _PyLongValue {
  uintptr_t lv_tag; /* Number of digits, sign and flags */
@@ -876,14 +876,18 @@ def proxyval(self, visited):
 
  struct _longobject {
  PyObject_HEAD
- _PyLongValue long_value;
+  _PyLongValue long_value;
  };
 
  with this description:
  The absolute value of a number is equal to
- SUM(for i=0 through abs(ob_size)-1) ob_digit[i] * 2**(SHIFT*i)
- Negative numbers are represented with ob_size < 0;
- zero is represented by ob_size == 0.
+ SUM(for i=0 through ndigits-1) ob_digit[i] * 2**(PyLong_SHIFT*i)
+ The sign of the value is stored in the lower 2 bits of lv_tag.
+ - 0: Positive
+ - 1: Zero
+ - 2: Negative
+ The third lowest bit of lv_tag is reserved for an immortality flag, but is
+ not currently used.
 
  where SHIFT can be either:
  #define PyLong_SHIFT 30