Re: [Boost-users] [BGL] Unable to sort list of edge_descriptors

On Sun, Nov 7, 2010 at 1:20 AM, Peter Wright wrote: It is dicey in one way, in that it stores a *reference* to its Graph -

so if the SortByName object outlives the Graph then it could blow up spectacularly. But the alternative of copying the entire graph seemed a bit excessive.

Another way to fix it (and also avoid the reference-storing problem) requires using Boost::Bind - change SortByName to this:

<snip/> ...and the A.sort call to this:

A.sort( boost::bind(SortByName(), g, _1, _2) );

It does avoid the reference-storing problem. I believe it does so by copying the entire graph. boost::bind() stores its parameters by value. If that is in fact excessive, you could write: A.sort( boost::bind(SortByName(), boost::ref(g), _1, _2) ); Now you're passing a reference again. It's unfortunate that you have to know whether a given function stores its parameters to know whether passing a reference might incur lifespan troubles. My impulse would be to think: "Hmm, sort(), I see no reason why any of its parameters should persist beyond its return." I assume that the whole boost::bind() value will be destroyed on return from sort(), therefore the bound reference to g as well.