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

[David-Sarah Hopwood]

Gavin Lambert wrote:
> At 13:05 24/09/2009, Jim Idle wrote:
>>Some platforms define this to be undefined though. Remember there
>>are lots if embedded systems that use this. Hence the qualification.
>>I think it would have been better to define free(NULL) as safe
>>myself but early Lib C would crash if you did this and I think it
>>was C++ that first took a stand?
> 
> I haven't looked at the standards recently, but from what I recall
> "delete NULL;" is guaranteed safe but "free(NULL);" wasn't.

C89 clause 4.10.3.2:

# The free function causes the space pointed to by ptr to be
# deallocated, that is, made available for further allocation.
# If ptr is a null pointer, no action occurs. [...]

(This is the same in C89 and C99; in the latter it is clause 7.20.3.2.)

> I definitely recall seeing some static testers and malloc replacements
> (some for performance, some for allocation debugging) that reacted badly
> to use of "free(NULL);" (sometimes just a failed assertion, sometimes
> worse).

That would be a bug. C89 is 20 years old; there's really no excuse for
writers of testers and malloc replacements not to have read the sections
of it that directly apply to them.

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