bpo-36465: Fix test_regrtest on Windows (GH-12945)

Fix Py_DEBUG constant: check for sys.gettotalrefcount attribute
rather than sys.getobjects.

Update also SpecialBuilds.txt documentation.

Lib/test/test_regrtest.py

@@ -21,7 +21,7 @@ from test import support
 from test.libregrtest import utils
 
 
-Py_DEBUG = hasattr(sys, 'getobjects')
+Py_DEBUG = hasattr(sys, 'gettotalrefcount')
 ROOT_DIR = os.path.join(os.path.dirname(__file__), '..', '..')
 ROOT_DIR = os.path.abspath(os.path.normpath(ROOT_DIR))
 

Misc/SpecialBuilds.txt

@@ -30,6 +30,8 @@ name "_" holds a reference to the last result displayed!
 Py_REF_DEBUG also checks after every decref to verify that the refcount hasn't
 gone negative, and causes an immediate fatal error if it has.
 
+Py_DEBUG implies Py_REF_DEBUG.
+
 Special gimmicks:
 
 sys.gettotalrefcount()
@@ -39,6 +41,8 @@ sys.gettotalrefcount()
 Py_TRACE_REFS
 -------------
 
+Build option: ``./configure --with-trace-refs``.
+
 Turn on heavy reference debugging.  This is major surgery.  Every PyObject grows
 two more pointers, to maintain a doubly-linked list of all live heap-allocated
 objects.  Most built-in type objects are not in this list, as they're statically
@@ -49,8 +53,6 @@ has been created.
 Note that because the fundamental PyObject layout changes, Python modules
 compiled with Py_TRACE_REFS are incompatible with modules compiled without it.
 
-Py_TRACE_REFS implies Py_REF_DEBUG.
-
 Special gimmicks:
 
 sys.getobjects(max[, type])
@@ -138,7 +140,8 @@ look at the object, you're likely to see that it's entirely filled with 0xDB
 (meaning freed memory is getting used) or 0xCB (meaning uninitialized memory is
 getting used).
 
-Note that PYMALLOC_DEBUG requires WITH_PYMALLOC.
+Note that PYMALLOC_DEBUG requires WITH_PYMALLOC. Py_DEBUG implies
+PYMALLOC_DEBUG (if WITH_PYMALLOC is enabled).
 
 Special gimmicks:
 
@@ -156,7 +159,7 @@ Py_DEBUG
 
 This is what is generally meant by "a debug build" of Python.
 
-Py_DEBUG implies LLTRACE, Py_REF_DEBUG, Py_TRACE_REFS, and PYMALLOC_DEBUG (if
+Py_DEBUG implies LLTRACE, Py_REF_DEBUG, and PYMALLOC_DEBUG (if
 WITH_PYMALLOC is enabled).  In addition, C assert()s are enabled (via the C way:
 by not defining NDEBUG), and some routines do additional sanity checks inside
 "#ifdef Py_DEBUG" blocks.
@@ -223,3 +226,5 @@ the interpreter is doing are sprayed to stdout, such as every opcode and opcode
 argument and values pushed onto and popped off the value stack.
 
 Not useful very often, but very useful when needed.
+
+Py_DEBUG implies LLTRACE.