(Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.)
+* Integers are now stored internally either in base 2**15 or in base
+ 2**30, the base being determined at build time. Previously, they
+ were always stored in base 2**15. Using base 2**30 gives
+ significant performance improvements on 64-bit machines, but
+ benchmark results on 32-bit machines have been mixed. Therefore,
+ the default is to use base 2**30 on 64-bit machines and base 2**15
+ on 32-bit machines; on Unix, there's a new configure option
+ --enable-big-digits that can be used to override this default.
+
+ Apart from the performance improvements this change should be
+ invisible to end users, with one exception: for testing and
+ debugging purposes there's a new structseq ``sys.long_info`` that
+ provides information about the internal format, giving the number of
+ bits per digit and the size in bytes of the C type used to store
+ each digit::
+
+ >>> import sys
+ >>> sys.long_info
+ sys.long_info(bits_per_digit=30, sizeof_digit=4)
+
+
+ (Contributed by Mark Dickinson; :issue:`4258`.)
+
+
.. ======================================================================
#define PyLong_MASK ((digit)(PyLong_BASE - 1))
#if PyLong_SHIFT % 5 != 0
-#error "longobject.c requires that SHIFT be divisible by 5"
+#error "longobject.c requires that PyLong_SHIFT be divisible by 5"
#endif
/* Long integer representation.