If the first item can't be inserted the interpreter will crash eventually. while 1:	try:	d = { 'a':a, 'b':'b', 'c':'c', 'd':'d', 'e':'e', 'f':'f', 'g':'g', 'h':'h', 'i':'i', 'j':'j', 'k':'k', 'l':'l', 'm':'m', 'n':'n', 'o':'o' }	except:	pass As best I can tell, this only happens for the first item. In a debug build, this assert fails on the second time thru the loop (dictobject.c, line 247):	assert (mp->ma_table == mp->ma_smalltable); Apparently something is leaving one of the entries in the list of preallocated dict objects in an inconsistent state.

Also happens in trunk.

The problem is that PyDict_New doesn't reinitialize the fields of a dict from the free list when the number of entries is zero. For a preconstructed dict (like created by BUILD_MAP) of size >=8, however, there will be an allocated ma_table and ma_mask will be 16-1, not 8-1. I propose the attached patch.

Applied and added test in r65637.