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Re: possible gawk memory leak?

From: david kerns
Subject: Re: possible gawk memory leak?
Date: Fri, 25 Jun 2021 06:20:01 -0700

I think you've mis-labeled the behavior. A memory leak is when you allocate
some memory and then either don't free it, or fail to free all that you
allocated, which becomes most problematic when it's done in a loop.

the program you submitted is not leaking, it's just consuming all available
/dev/zero is an infinite generator of zeros
awk happily reads "record 1" into memory looking for the inevitable EOL/EOR

On Fri, Jun 25, 2021 at 6:06 AM Eckard Brauer <eckard.brauer@gmx.de> wrote:

> Hello,
> playing around I just observed a little problem with gawk I can't
> really explain well (gawk-5.1.0, Linux (Gentoo), x86_64). Executing
> awk 'NR==4{exit}{print NR}' /dev/zero
> gawk tries to allocate all available memory and so freezes the whole
> host for some time. Doing that in a memory limited environment to
> preserve disk swapping only let's happen the crash earlier and without
> system freeze:
>  $ ulimit -m 8192000
>  $ ulimit -v 8192000
>  $ awk 'NR==4{exit}{print NR}' /dev/zero
> awk: fatal: io.c:3464:grow_iop_buffer: iop->buf: cannot reallocate
> 8589934593 bytes of memory: Cannot allocate memory
> So if that's not an individual problem, could you either explain the
> reason(s) for that behaviour, or fix it if it's unintended?
> Thanks in advance && best regards,
> Eckard Brauer

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