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NNTP-Posting-Date: Fri, 19 Oct 2012 22:13:49 -0500
From: Steve Thompson <stevet810@gmail.com>
Newsgroups: comp.lang.c
Subject: Compatibility question
Date: Sat, 20 Oct 2012 03:08:30 +0000
Organization: Friends of the Galactic Collective
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Xref: csiph.com comp.lang.c:27400

I have been using structures containing zero-length arrays as a means
of combining descriptors and array data in a single allocation unit.
Something like the following is a common idiom:

struct foo {
   int     a, b;
   size_t  len;
   char    p[0];
};

struct foo *q;


For the noobs, q->p[x] is obviously convenient, however before gcc
supported zero-length arrays, the arrangement would be something like
this:

struct foo {
   int     a, b;
   size_t  len;
};

struct foo *q;
char *x;

In this instance, assuming that the array of char is intended to be
available immediately following struct foo, the access is done as
follows:

*((char *)(q + 1)) = ' ';

So far, so good.  My questions regards the availability of zero-length
arrays in common systems.  That is, if I wish my code to be compatible
with most C compilers in use today, should I worry about avoiding
zero-length arrays, or is the feature old enough, with sufficient
prevalence to make it's use reasonable in portable code?



Regards,

Steve Thompson

-- 
GOTO's are like guns.  Safety is entirely contingent on the user.