Looking closer at cPickle.c (after upgrading my GCC), I think there are two warnings happening, when Pdata_clear() is inlined into each of noload_reduce() and noload_setitem(). I think both cases are false positives; there is no actual signed overflow possible. Ismail Donmez has provided patches that work around this warning in Issue 1621, but IMO, and maybe in the general consensus, we shouldn’t add these workarounds.