Data members that want to use size()

The following snippet doesn’t compile: struct A { static constexpr size_t size() { return 42; } int data_[size()]; }; The problem is that the size (and therefore the type) of data member data_ can’t be computed until we know the value of size(); but evaluating size() requires A to be complete ([class.mem.general]), which won’t happen until the closing brace on the next line. One workaround, obviously, is to repeat the magic number 42 in two places. That’s probably the simplest option; but here are a few other workarounds.

Source: https://quuxplusone.github.io/blog/2026/08/25/size-idioms. 8 Sync News only summarizes and links out; content copyright belongs to the authors and original sources.