Hi, Thanks for this pointer, very interesting and commented
So we have to be double careful when using memcpy though, even if it acts faster than its cousin memmove ! Nicolas Le samedi 08 janvier 2011 ? 09:43 +0100, Julien BLACHE a ?crit : > Nicolas Martin <nicolas0martin at gmail.com> wrote: > > Hi, > > > What is weird here, is that the effect of overlap in memcpy does not > > seem to produce the same effect on different systems ! > > Using memcpy() on overlapping memory areas is undefined behaviour per > spec. > > glibc has several memcpy() implementations optimized for different > hardware capabilities. A recent implementation for Atom/Core2 CPUs > performs the copy from tail to head (giving a nice 4x/5x speedup on > these CPUs), which breaks with overlapping memory areas. > > Using memmove() is the correct way to handle overlapping areas, as > documented. > > See <http://lwn.net/Articles/414467/> for more (links/comments). > > HTH, > > JB. >
