[antlr-interest] Updates for release 3.2 of the C Target

[David-Sarah Hopwood]

Jim Idle wrote:
> The following should be read carefully before upgrading to release 3.2
> of the C target:
[...]
>    * finally - this code is executed whether the rule parses
>      successfully or not. This is probably where you should free
>      allocations, but you should guard against uninitialized elements,
>      which may not have been created on a parse error.

Are such elements (not variables that you declare yourself) guaranteed
to be NULL?

>    * Because you can end up executing both @after and finally code, use
>      safe programming patterns (you should be anyway ;-, and assign
>      NULL to anything after declaring it and immediately before freeing
>      it.

You mean immediately after freeing it :-)
(i.e. "free(foo); foo = NULL;")

>      Also, guard against free(NULL) unless the semantics of your
>      system specify that free(NULL) is allowed.

"free(NULL)" is defined to be a no-op by the C standard. A libc
implementation that got this wrong would be badly broken, and AFAIK all
the commonly used platforms get it right.

-- 
David-Sarah Hopwood  ⚥  http://davidsarah.livejournal.com