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Re: heap memory indexed as an array

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On Wed, 20 Mar 2019 16:43:53 GMT, scott@slp53.sl.home (Scott Lurndal)
wrote:

>nobody@example.org (Scott) writes:
>>On Wed, 20 Mar 2019 04:40:25 GMT, Spiros Bousbouras <spibou@gmail.com>
>>wrote:
>>
>>>But you don't get to do error checking either and if there isn't enough
>>>memory to allocate the array , the programme will probably crash with an
>>>uninformative error message.
>>
>>Well, maybe. On some contemporary operating systems, a malloc return
>>value of non-null does not guarantee that the allocated memory
>>actually exists. It can appear to succeed, and only explodes when you
>>try to write to that phantom memory -- and there's no way to trap that
>>fault in C.
>
>Correction, no "standard C" method.   One may always catch SIGSEGV.

Agreed, one may do so, *if* the signal is sent. Seg fault happens when
you hit memory that isn't yours, but in the case of overcommit, the
page *is* yours, it just doesn't have any memory behind it. My
experiences here are brief and not conclusive at all, but when I wrote
a test program to really push the issue, the result was crashing the
entire OS more often than not, with no (catchable) signal ever sent to
my process.

Well, now I'm curious about what I'm forgetting. I'll see about
setting up a test box and re-run that experiment on a few different
OSes.

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Thread

heap memory indexed as an array sinbad <sinbad.sinbad@gmail.com> - 2019-03-19 20:05 -0700
  Re: heap memory indexed as an array Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-03-19 21:37 -0600
    Re: heap memory indexed as an array Spiros Bousbouras <spibou@gmail.com> - 2019-03-20 04:40 +0000
      Re: heap memory indexed as an array nobody@example.org (Scott) - 2019-03-20 15:56 +0000
        Re: heap memory indexed as an array scott@slp53.sl.home (Scott Lurndal) - 2019-03-20 16:43 +0000
          Re: heap memory indexed as an array fir <profesor.fir@gmail.com> - 2019-03-20 10:00 -0700
          Re: heap memory indexed as an array William Ahern <william@25thandClement.com> - 2019-03-20 15:07 -0700
            Re: heap memory indexed as an array fir is a sexy shemale <cdalten@gmail.com> - 2019-03-20 23:52 -0700
          Re: heap memory indexed as an array nobody@example.org (Scott) - 2019-03-21 16:50 +0000
            Re: heap memory indexed as an array scott@slp53.sl.home (Scott Lurndal) - 2019-03-21 17:23 +0000
              Re: heap memory indexed as an array nobody@example.org (Scott) - 2019-03-22 04:29 +0000
                OT: crashing malloc [was Re: heap memory indexed as an array] nobody@example.org (Scott) - 2019-03-23 15:27 +0000
                Re: heap memory indexed as an array Spiros Bousbouras <spibou@gmail.com> - 2019-03-23 19:24 +0000
                Re: heap memory indexed as an array Melzzzzz <Melzzzzz@zzzzz.com> - 2019-03-23 20:20 +0000
      Re: heap memory indexed as an array Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-03-21 22:35 -0700
  Re: heap memory indexed as an array Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-03-20 07:05 +0000
  Re: heap memory indexed as an array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-20 12:12 +0000

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