Hacker News Reader

Comment by silentvoice | Hacker News Reader

Could someone comment on the following C++14 feature on the list here:

"Avoiding/fusing memory allocations"

It lists Clang but nothing else as supporting it.

This sounds like a compiler optimization and not a language feature, and since it's talking about C++14 (not C++11) I know this isn't referring to move semantics/rvalue references.

What exactly is this?

View on HN

That is a clarification [1] to the standard, to make it legal to avoid or fuse memory allocations if the compiler can prove it's OK. For example,

   int f() {
     int * x = new int(0);
     return *x;
   }

does not really need to allocate memory, and so that `new` is now explicitly allowed not to. Similarly,

   int f() {
     int * x = new int(0);
     int * y = new int(1);
     return *x + *y;
   }

Here the standard allows not only to elide both allocations, but also to fuse them into a single (faster) allocation.

[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n366...

Reply on news.ycombinator.com