gotw 056 Exception-Safe Function Calls

NOTE: 在 阅读 stackoverflow Exception safety and make_unique 的如下comment中，发现的这篇文章:

multiple allocations in an expression but each of those allocations via new T is a separate expression, so you have the opposite: one allocation per each of multiple expressions. That the function call is itself an expression containing the other 2 doesn't change that. But aside from the wording, you were on the right track. By my reading, the rule, as formulated by Sutter, is to perform each allocation within its own statement or sequence them by returning from a separate function call, thereby avoiding weird ordering & leaks: gotw.ca/gotw/056.htm (oldie-but-goodie) – underscore_d Aug 13 '16 at 11:25