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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: local arrays and stack
Date: Mon, 23 Mar 2015 12:48:17 -0700
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Xcott Craver <xcottcraver@gmail.com> writes:
> On Monday, March 23, 2015 at 1:37:23 PM UTC-4, Keith Thompson wrote:
>> Xcott Craver <@> writes:
>> > I can declare a 160MB array and see it on the stack.  It's just a matter
>> > of subtracting the relevant offset from the stack pointer.
>> 
>> Using what implementation?
>
> 64-bit OSX:
>
> #define LEN 40000000
> int main( void ) {
>         int array [LEN];  ....
>
> (lldb) disas --name main
> a.out`main at tester.c:12:
> a.out[0x100000ec0]:  pushq  %rbp
> a.out[0x100000ec1]:  movq   %rsp, %rbp
> a.out[0x100000ec4]:  subq   $0x9896820, %rsp  <---- 160000032 bytes
>
> The ulimit command tells me that I apparently have an 8192K soft limit, and a
> 65532K hard limit on the stack.  However, I can declare gigabyte-sized arrays,
> and dissassembly just shows the function subtracting insane amounts from the
> stack pointer.

I tried something similar on my system (Linux Mint, x86_64).  When I
just declared the array, the program compiled and ran without error.
When I assigned a value to an element near the end of the array, it died
with a segmentation fault.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"