Re: OT: Language War (Re: "C" Manual)

[William T Wilson <fluffy@snurgle.org>]

On Sat, 5 Jan 2002, Eric G.Miller wrote:

> is one of the reasons pointers to char are so common.  However, there
> is a little trick that's guaranteed to always work:
> 
>  struct foo {
> 	size_t length;
> 	char str[1];
>  };
> 
>  ...
> 
> struct foo * str_to_foo(char *a)
> {
>   size_t len = strlen (a);
>   struct foo *bar = malloc (sizeof(struct foo) + len);
>   if (bar) {
>     bar->length = len;
>     memcpy (bar->str, a, len);  /* bar->str now not NUL terminated */
>   }
>   return bar;
> } 

It doesn't look particularly guaranteed to me.  You're really allocating
*three* pieces of memory here - one for the struct foo, one for the
1-character array chr, and one for the rest of the string.  Your example
assumes that chr will be located in memory immediately after foo - which
it probably will, but it might not.  It could be anywhere, the language
makes no guarantee.  The compiler might even choose to put the 1-char
array before foo, so you can't use it without overwriting your struct

Structs have fields.  Use them.

> The benefit is being able to use one malloc vs. two (for any similarly

This is a benefit why? :}