On 09/04/2014 08:03 PM, Paul Eggert wrote:

> For vectors the macro needs to generate a series of declarations and
> statements  rather than an expression.  It's less clean, but it's good
> enough.  Something like the attached, say.

IMO this is a bit overengineered.  In particular, the whole thing is to
allocate short-lived objects which are usually small. This means that
!issmall branch is unlikely to be taken but requires SAFE_xxx anyway.
Moreover, I think we need a very special benchmark to see a difference
between alloca and VLA (if any), thus using the latter at any cost doesn't
worth an extra complexity.  So, although I have no strong objections
about your version, I'm voting for simpler and cleaner version with
alloca/fallback to regular GC for vectors and strings.  Stefan?

Dmitry