 <p><a href="http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html" rel="nofollow">Cellperformance</a> states that strict aliasing is:</p> <blockquote> <p>[...] an assumption, made by the C (or C++) compiler, that dereferencing pointers to objects of different types will never refer to the same memory location (i.e. alias eachother.)</p> </blockquote> <p>This warning occurs when <code>-fno-strict-aliasing</code> and optimizations (<code>-O2</code> or higher) are enabled because the compiler needs to be much more conservative when its accessing (possibly) aliased memory. This leads to less optimizations - the compiler can't e.g. really be sure that elements doesn't overlap (see example in article posted above).</p> <p>This is not a warning you should worry about - the Boost developers are probably aware of this and have good reasons to why this is ok.</p>