Path: utzoo!attcan!uunet!jarthur!uci-ics!gateway
From: schmidt@crimee.ics.uci.edu (Doug Schmidt)
Newsgroups: comp.lang.c++
Subject: Re: Renew?
Keywords: memory allocation
Message-ID: <26601546.25889@paris.ics.uci.edu>
Date: 27 May 90 17:58:30 GMT
References: <1990May25.013535.16930@cbnewsl.att.com>
Reply-To: schmidt@crimee.ics.uci.edu (Doug Schmidt)
Organization: University of California, Irvine - Dept of ICS
Lines: 44
In-reply-to: bill@cbnewsl.att.com (william.clark)

In article <1990May25.013535.16930@cbnewsl.att.com>, bill@cbnewsl (william.clark) writes:
>C has malloc() and C++ has new
>C has remalloc() could C++ have "renew"?
>
>It would save me some time shifting class contents around as the objects
>accrue data.  (I know I could simple use malloc() and realloc() and might
>even save some time but I'd rather stick to new).

The GNU libg++ library has an extension along these lines in the
<new.h> file:

----------------------------------------
// provide a C++ interface to vector-resize via realloc
static inline void *operator new(size_t size, void *ptr, size_t new_len)
{
  return realloc(ptr, new_len * size);
}
----------------------------------------

You use this extension as follows:

----------------------------------------
void resize (size_t elem_size, void *old_ptr, int new_size)
{
  // The following line uses overloaded operator new to
  // emulate realloc.
  return new {old_ptr, new_size * elem_size} char;
}
----------------------------------------

Note that g++ uses { } as the delimiters for the placement syntax,
cfront 2.0 would use ( ), e.g.:

  return new (old_ptr, new_size * elem_size) char;

Note that since operator new is declared inline there should be no
additional function call overhead for using this `re'new abstraction.

Doug
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