&gt;btw. I&#x27;m pretty sure I heard that glibc broke this behavior sometime recently.<p>You are perhaps thinking of this: <a href="https:&#x2F;&#x2F;sourceware.org&#x2F;bugzilla&#x2F;show_bug.cgi?id=12518" rel="nofollow">https:&#x2F;&#x2F;sourceware.org&#x2F;bugzilla&#x2F;show_bug.cgi?id=12518</a><p>I&#x27;m not sure if that change broke glibc memcpy for identical arguments or just ones that were different but overlapped.<p>This quote suggests that Drepper wouldn&#x27;t have had any problem breaking things that passed identical arguments to memcpy:<p>&gt;The existence of code written by people who should never have been allowed to touch a keyboard cannot be allowed to prevent a correct implementation.