Re: C++ Memory Management Question

From	Victor Bazarov <v.bazarov@comcast.invalid>
Newsgroups	comp.lang.c++
Subject	Re: C++ Memory Management Question
Date	2011-12-31 09:44 -0500
Organization	A noiseless patient Spider
Message-ID	<jdn74b$fbi$1@dont-email.me> (permalink)
References	<nn4uf7hmc7c5r5jac8cq8qjhsguk8alh77@4ax.com>

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On 12/31/2011 8:56 AM, Datesfat Chicks wrote:
> I'm just learning C++ (after being a 19-year C veteran), so forgive
> any naive questions or concerns.
>
> It seems to me that C++ has more inherent reliance on dynamic memory
> allocation than C.  It doesn't have to be that way in all cases (many
> classes would be implemented without dynamic allocation), but it seems
> more natural in C++ that dynamic allocation would appear in programs.

The reality is simpler: it's easier to do dynamic memory properly in C++ 
(purposefully so, actually), and that's the reason more people resort to 
it.  In fact I've written plenty of code that never allocated anything 
in the free store (except by any library mechanisms that I had no 
control over).  You don't have to use dynamic memory if you don't need it.

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

That's not a question, you know.  And, they are.

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

Usually.  Unless you've overridden 'new' and 'delete' and made THEM 
"draw" from some other place.

> My reason for asking that question is that I'm looking for a graceful
> strategy if dynamic memory gets exhausted.

Good luck.

> The obvious strategy that comes to mind is:
>
> a)When the program starts, grab a good chunk of memory using malloc().

And do what with it?  Just sit on it?  That's a serious waste of memory.

> 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.

Explain "gracefully exit".  I mean, explain it to yourself, keeping in 
mind that your process was *interrupted* by a *failed attempt* to get 
more memory.

> c)Hopefully the memory released by free() would be enough to allow the
> program to exit gracefully (rather than a sudden less controlled
> exit).

So, your strategy is "reserve [a preset amount of] some resource until 
it's desperately needed, then release it and pray that it's enough to 
kill the process", right?

> Is this sane?

How about I don't answer this, and you instead get a second look at it 
at your convenience?

 >  Is there a better way?

This question is asked here countless times every year.  How about *you* 
google for it and try to find out how successful your predecessors were? 
  And if you find something that suits you, by all means use it.  If you 
don't, *and* you have spare time, by all means look for it.  But my 
advice (based on experience trying to handle it and seeing others trying 
to handle it) is, don't waste your time.  If your process has run out of 
memory, the best solution is to restart it with *more memory*.

And, again, good luck!

V
-- 
I do not respond to top-posted replies, please don't ask

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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