🚀 go-pugleaf

In article <4kr7b2$kcb@solutions.solon.com>,
stanr@tiac.net (Stan Ryckman) wrote:
>
>Your example is too simple; that's an obvious conversion.
>Much more difficult is where alloca() has been used in a loop, to
>(for example) build a linked list (or worse) on the stack, and
>"return" has been used to free all the spaghetti.

Yes, quite.

If you want to see how hard it is to define semantics for alloca that
are tight enough to allow scope checking and flexible enough to allow
the creation of linked lists, look at the Algol 68 scoping rules.  It
is a foul problem, which is why alloca is not always provided.

>And, in answer to the original poster's question, yes, implementations
>without alloca() do exist; I had to port such spaghetti to one
>(some version of Venix) and it was a real mess.

Actually, there are far more mainstream systems without alloca, and
even HP-UX did not have it until recently.  Your point stands :-)


Nick Maclaren,
University of Cambridge Computer Laboratory,
New Museums Site, Pembroke Street, Cambridge CB2 3QG, England.
Email:  nmm1@cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679