Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #9557

Re: "struct hack" with non-character array[1]

Show all headers | View raw

Ian Collins <ian-news@hotmail.com> writes:

> On 08/19/11 10:28 PM, Hallvard B Furuseth wrote:
>> I seem to remember the "struct hack" is safer if the fake
>> dynamic array has character type.  If that's right, where/why?
>
> Why should it be?

No idea, so I asked here.  It's just something I remember, but I
can't remeber from where.  Maybe from long ago, since the hack
was shot down by stages.

>> Maybe in C99, since the struct hack is undefined in C89?  Or
>> real life implementations, nothing to do with the standard?
>>
>> That is,
>>     typedef<char or int>  T;
>>     struct hack { Foo foo; T dynamic[1]; };
>
> make that
> struct hack { Foo foo; T dynamic[]; };
> for C99.

Nope, not my question.

>>     struct hack h = malloc(sizeof *h) + sizeof(T)*n;
>>     .... use h->dynamic[0..n-1] ...;
>> would be safer with T = char than with T = int.
>
> It wouldn't compile with either.  The flexible array member is irrelevant.

Yes, should be malloc(sizeof *h + sizeof(T)*n) like Eric said.

-- 
Hallvard B Furuseth                 tlf:   +47-22 85 28 13
USIT

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

"struct hack" with non-character array[1] Hallvard B Furuseth <h.b.furuseth@usit.uio.no> - 2011-08-19 12:28 +0200
  Re: "struct hack" with non-character array[1] Ian Collins <ian-news@hotmail.com> - 2011-08-19 23:15 +1200
    Re: "struct hack" with non-character array[1] Hallvard B Furuseth <h.b.furuseth@usit.uio.no> - 2011-08-19 15:12 +0200
    Re: "struct hack" with non-character array[1] falk@rahul.net (Edward A. Falk) - 2011-08-19 16:41 +0000
  Re: "struct hack" with non-character array[1] Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-19 08:01 -0400
  Re: "struct hack" with non-character array[1] James Kuyper <jameskuyper@verizon.net> - 2011-08-19 08:40 -0400
  Re: "struct hack" with non-character array[1] Keith Thompson <kst-u@mib.org> - 2011-08-19 09:41 -0700

csiph-web