Re: C++ Memory Management Question

From	Torsten Mueller <dev-null@shared-files.de>
Newsgroups	comp.lang.c++
Subject	Re: C++ Memory Management Question
Date	2011-12-31 16:41 +0100
Message-ID	<87vcow7npx.fsf@castor.ch> (permalink)
References	<nn4uf7hmc7c5r5jac8cq8qjhsguk8alh77@4ax.com>

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Datesfat Chicks <datesfat.chicks@gmail.com> schrieb:

> a)I'm assuming that malloc() and free() are still available in C++?

Yes, they are. And also other platform dependend functions, too
(realloc, calloc).

> b)Do these draw from the same memory pool as "new" and "delete"?

Yes, they do. Normally new and delete are just wrappers. They call
malloc and free internally. But there's no guarantee for this, they can
also use other strategies, but the pool is truely the same.

Note:

- It is not guaranteed that new and free or malloc and delete are
  compatible. Never mix this!

- There are two deletes: delete and delete[].

The best way to write clean, safe and portable C++ code is to FORGET the
existence of malloc and free (and all the other alloc-functions, strdup
and others) completely. NEVER USE these functions. You can do everything
(except reallocation) with new and delete.

> My reason for asking that question is that I'm looking for a graceful
> strategy if dynamic memory gets exhausted.
>
> The obvious strategy that comes to mind is:
>
> a)When the program starts, grab a good chunk of memory using malloc().
>
> b)If the dynamic memory gets exhausted via "new" and friends, handle
> the exception.  In the exception handler, free() the memory allocated
> by (a) and set a flag to signal the program to gracefully exit as soon
> as it can.
>
> c)Hopefully the memory released by free() would be enough to allow the
> program to exit gracefully (rather than a sudden less controlled
> exit).

There's no need for the initial malloc call. You can allocate the chunk
also by new and free it by delete.

But I would avoid this topic completely. I think the need to react on
memory exaustion is very few, especially if you just learn the language.
If this really happens something else is wrong.

A "memory management" case that is much more interesting (because it
really happens) is stack overflow. The stack overflow is amazing: you
will not be able to call any further function because there's just no
space left on the damned stack ...

T.M.

Thread

C++ Memory Management Question Datesfat Chicks <datesfat.chicks@gmail.com> - 2011-12-31 08:56 -0500
  Re: C++ Memory Management Question Victor Bazarov <v.bazarov@comcast.invalid> - 2011-12-31 09:44 -0500
    Re: C++ Memory Management Question Datesfat Chicks <datesfat.chicks@gmail.com> - 2011-12-31 10:17 -0500
      Re: C++ Memory Management Question "MikeWhy" <boat042-nospam@yahoo.com> - 2011-12-31 12:56 -0600
      Re: C++ Memory Management Question jt@toerring.de (Jens Thoms Toerring) - 2011-12-31 19:05 +0000
    Re: C++ Memory Management Question Carlo Milanesi <carlo.nospam.milanesi@libero.it> - 2011-12-31 18:18 +0100
      Re: C++ Memory Management Question Victor Bazarov <v.bazarov@comcast.invalid> - 2011-12-31 13:04 -0500
        Re: C++ Memory Management Question Carlo Milanesi <carlo.nospam.milanesi@libero.it> - 2011-12-31 19:42 +0100
        Re: C++ Memory Management Question Goran <goran.pusic@gmail.com> - 2011-12-31 23:25 -0800
          Re: C++ Memory Management Question Victor Bazarov <v.bazarov@comcast.invalid> - 2012-01-01 09:39 -0500
            Re: C++ Memory Management Question Goran <goran.pusic@gmail.com> - 2012-01-01 08:20 -0800
            Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-01 19:05 +0000
              Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-01 19:36 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-01 19:49 +0000
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-02 11:26 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-02 14:32 +0000
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-02 15:54 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-02 16:26 +0000
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-02 16:58 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-02 21:14 +0000
                Re: C++ Memory Management Question Ian Collins <ian-news@hotmail.com> - 2012-01-03 11:11 +1300
                Re: C++ Memory Management Question scott@slp53.sl.home (Scott Lurndal) - 2012-01-03 20:53 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-03 21:21 +0000
                Re: C++ Memory Management Question Ian Collins <ian-news@hotmail.com> - 2012-01-04 12:15 +1300
                Re: C++ Memory Management Question gwowen <gwowen@gmail.com> - 2012-01-04 08:20 -0800
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-02 22:24 +0000
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-02 22:55 +0000
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-02 23:27 +0000
                Re: C++ Memory Management Question Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-10 01:01 -0800
                Re: C++ Memory Management Question 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-02 21:45 -0800
                Re: C++ Memory Management Question Goran <goran.pusic@gmail.com> - 2012-01-03 00:32 -0800
                Re: C++ Memory Management Question "Paul" <pchrist<nospam>or@yahoo.co.uk> - 2012-01-03 17:34 +0000
                Re: C++ Memory Management Question Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-10 00:47 -0800
                Re: C++ Memory Management Question BCFD36 <bcfd36@cruzio.com> - 2012-01-10 22:57 -0800
              Re: C++ Memory Management Question Ian Collins <ian-news@hotmail.com> - 2012-01-03 09:31 +1300
                Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-02 21:02 +0000
                Re: C++ Memory Management Question Ian Collins <ian-news@hotmail.com> - 2012-01-03 11:09 +1300
          Re: C++ Memory Management Question Leigh Johnston <leigh@i42.co.uk> - 2012-01-01 18:57 +0000
      Re: C++ Memory Management Question jgk@panix.com (Joe keane) - 2012-01-01 22:04 +0000
        Re: C++ Memory Management Question Carlo Milanesi <carlo.nospam.milanesi@libero.it> - 2012-01-02 00:37 +0100
          Re: C++ Memory Management Question yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2012-01-09 17:41 +0000
            Re: C++ Memory Management Question Carlo Milanesi <carlo.milanesi@libero.it> - 2012-01-13 08:14 -0800
    Re: C++ Memory Management Question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-01 18:05 +0000
  Re: C++ Memory Management Question Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-12-31 07:25 -0800
  Re: C++ Memory Management Question Torsten Mueller <dev-null@shared-files.de> - 2011-12-31 16:41 +0100
  Re: C++ Memory Management Question Nobody <nobody@nowhere.com> - 2012-01-01 09:16 +0000
    Re: C++ Memory Management Question Datesfat Chicks <datesfat.chicks@gmail.com> - 2012-01-02 16:48 -0500
      Re: C++ Memory Management Question Goran <goran.pusic@gmail.com> - 2012-01-03 00:02 -0800
        Re: C++ Memory Management Question Datesfat Chicks <datesfat.chicks@gmail.com> - 2012-01-03 12:53 -0500
          Re: C++ Memory Management Question Nobody <nobody@nowhere.com> - 2012-01-03 19:46 +0000
          Re: C++ Memory Management Question Goran <goran.pusic@gmail.com> - 2012-01-04 00:11 -0800
            Re: C++ Memory Management Question Nobody <nobody@nowhere.com> - 2012-01-04 09:30 +0000
    Re: C++ Memory Management Question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-04 19:28 +0000
      Re: C++ Memory Management Question Nobody <nobody@nowhere.com> - 2012-01-04 22:09 +0000
        Re: C++ Memory Management Question Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-05 11:43 +0000
  Re: C++ Memory Management Question Christian Gollwitzer <auriocus@gmx.de> - 2012-01-01 18:13 +0100
    Re: C++ Memory Management Question "io_x" <a@b.c.invalid> - 2012-01-01 20:11 +0100
    Re: C++ Memory Management Question Datesfat Chicks <datesfat.chicks@gmail.com> - 2012-01-02 16:51 -0500
  Re: C++ Memory Management Question Simon Quinn <sq@nospam.com> - 2012-01-05 07:54 +0000
  Re: C++ Memory Management Question darylew@gmail.com - 2012-01-10 10:19 -0800

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