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Re: Trying to figure out how to dynamically re-allocate strings while concatenating

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pete <pfiland@mindspring.com> writes:
[...]
> One thing that nobody else has mentioned, is that it is good
> programming practice to assign the return value of realloc to a
> temporary pointer first, and only to assign that value to your working
> pointer if the temporay pointer has been tested and found to be not a
> null pointer.
>
> Otherwise you lose the value of the pointer to the allocated memory,
> which can cause a memory leak.
[...]

That is, of course, very good advice.

On the other hand, whether it matters depends on what you intend to do
once you've detected an allocation failure.

    char *buf = malloc(100);
    if (buf == NULL) {
        /* malloc failed */
    }

    char *temp = realloc(buf, 200);
    if (temp == NULL) {
        /* realloc failed */
    }

So how can you recover from a failure to allocate memory?  You could
just try again, but it will probably just fail again.  You could fall
back to a less memory-intensive, but perhaps slower, algorithm, but
I don't think I've ever seen code in the real world that does that.

A very common response to a memory allocation failure is to
terminate the program, ideally after doing some cleanup (such as
saving temporary files, restoring the display to a sane state,
printing and/or logging an error message, etc.)  But if the
program is about to terminate anyway, then losing the pointer to
your original buffer isn't going to make much difference, and you
probably might as well write:

    buf = malloc(buf, 200);

On the other other hand, cleaning up after yourself is a good habit, and
it's possible that calling free(buf) will free up memory that's needed
by your cleanup code.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Trying to figure out how to dynamically re-allocate strings while concatenating Shriramana Sharma <jamadagni@gmail.com> - 2012-08-04 07:12 -0700
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2012-08-04 16:17 +0200
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2012-08-04 16:22 +0200
    Re: Trying to figure out how to dynamically re-allocate strings while concatenating Shriramana Sharma <jamadagni@gmail.com> - 2012-08-04 07:25 -0700
      Re: Trying to figure out how to dynamically re-allocate strings while concatenating Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-04 16:04 +0100
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating "Heinrich Wolf" <invalid@invalid.invalid> - 2012-08-04 16:29 +0200
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-04 10:52 -0400
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating pete <pfiland@mindspring.com> - 2012-08-04 12:27 -0400
    Re: Trying to figure out how to dynamically re-allocate strings while concatenating Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-04 13:56 -0400
      Re: Trying to figure out how to dynamically re-allocate strings while  concatenating pete <pfiland@mindspring.com> - 2012-08-04 17:12 -0400
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating pete <pfiland@mindspring.com> - 2012-08-04 12:42 -0400
    Re: Trying to figure out how to dynamically re-allocate strings while concatenating Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-04 14:00 -0400
    Re: Trying to figure out how to dynamically re-allocate strings while concatenating Keith Thompson <kst-u@mib.org> - 2012-08-04 17:00 -0700
      Re: Trying to figure out how to dynamically re-allocate strings while concatenating pete <pfiland@mindspring.com> - 2012-08-04 20:48 -0400
      Re: Trying to figure out how to dynamically re-allocate strings while concatenating Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-05 09:22 +0200
        Re: Trying to figure out how to dynamically re-allocate strings while concatenating Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-05 12:49 +0100
          Re: Trying to figure out how to dynamically re-allocate strings while concatenating Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-05 17:12 +0200
          Re: Trying to figure out how to dynamically re-allocate strings while concatenating Keith Thompson <kst-u@mib.org> - 2012-08-05 13:17 -0700
            Re: Trying to figure out how to dynamically re-allocate strings while concatenating Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-05 22:53 +0100
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating Shriramana Sharma <jamadagni@gmail.com> - 2012-08-04 19:20 -0700
  Re: C Vs Asm i use for cat function "io_x" <a@b.c.invalid> - 2012-08-05 08:15 +0200
    Re: C Vs Asm i use for cat function "BartC" <bc@freeuk.com> - 2012-08-05 10:22 +0100
      Re: C Vs Asm i use for cat function "Heinrich Wolf" <invalid@invalid.invalid> - 2012-08-05 17:00 +0200
        Re: C Vs Asm i use for cat function Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-05 16:20 +0100
      Re: C Vs Asm i use for cat function "io_x" <a@b.c.invalid> - 2012-08-05 19:51 +0200
        Re: C Vs Asm i use for cat function "BartC" <bc@freeuk.com> - 2012-08-05 21:04 +0100
  Re: Trying to figure out how to dynamically re-allocate strings while concatenating Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-08-10 10:45 +0300

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