Issue #13390: New function :func:sys.getallocatedblocks() returns the number of memory blocks currently allocated.

Also, the ``-R`` option to regrtest uses this function to guard against memory allocation leaks.

Objects/obmalloc.c

@@ -525,6 +525,15 @@ static size_t ntimes_arena_allocated = 0;
 /* High water mark (max value ever seen) for narenas_currently_allocated. */
 static size_t narenas_highwater = 0;
 
+static Py_ssize_t _Py_AllocatedBlocks = 0;
+
+Py_ssize_t
+_Py_GetAllocatedBlocks(void)
+{
+    return _Py_AllocatedBlocks;
+}
+
+
 /* Allocate a new arena.  If we run out of memory, return NULL.  Else
  * allocate a new arena, and return the address of an arena_object
  * describing the new arena.  It's expected that the caller will set
@@ -785,6 +794,8 @@ PyObject_Malloc(size_t nbytes)
     if (nbytes > PY_SSIZE_T_MAX)
         return NULL;
 
+    _Py_AllocatedBlocks++;
+
     /*
      * This implicitly redirects malloc(0).
      */
@@ -901,6 +912,7 @@ PyObject_Malloc(size_t nbytes)
                  * and free list are already initialized.
                  */
                 bp = pool->freeblock;
+                assert(bp != NULL);
                 pool->freeblock = *(block **)bp;
                 UNLOCK();
                 return (void *)bp;
@@ -958,7 +970,12 @@ redirect:
      */
     if (nbytes == 0)
         nbytes = 1;
-    return (void *)malloc(nbytes);
+    {
+        void *result = malloc(nbytes);
+        if (!result)
+            _Py_AllocatedBlocks--;
+        return result;
+    }
 }
 
 /* free */
@@ -978,6 +995,8 @@ PyObject_Free(void *p)
     if (p == NULL)      /* free(NULL) has no effect */
         return;
 
+    _Py_AllocatedBlocks--;
+
 #ifdef WITH_VALGRIND
     if (UNLIKELY(running_on_valgrind > 0))
         goto redirect;