On 11/09/2010 07:40 PM, Patrick Horgan wrote: > Most the confusion that I've seen in discussions of strict aliasing > rules has come from developers thinking that strict aliasing is a set of > rules telling them how to do type punning within the restrictions of the > standard. It's not about that at all. Instead it's a set of rules > telling compiler writers when they can't do some optimizations. Of > course developers who do type-punning do need to under- > stand these rules to make sure that their code doesn't > break in the presence of optimization. > > I've written a first draft of a short little paper on > this that I hope can be referred to whenever confusion > arises again. The audience is really developers who > use the compilers because the compiler writers already > understand this. Nevertheless, I've seen compiler > writers and others who work on standards bodies in > conversations where they just couldn't understand > why communication was not happening. They would > benefit from reading the introduction. > > http://dbp-consulting.com/StrictAliasing.pdf > > Some of it is derivative of the stuff I wrote on > the boost developers wiki about it, but in this I talk > a lot more about what strict aliasing is. > > I'm hoping people here who understand the issues will > read it and email me with any corrections, examples, > improvements etc. The aliasing rules are nothing to do with C99: they have always been in Standard C. You really ought to refer to the standard, so people can see the official rules for themselves. Andrew.
