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Subject: Re: Memory problems running C programs using GCC in NetBeans/Cygwin on Windows
To: cygwin AT cygwin DOT com
References: <001d01d2a297$c0761050$416230f0$@dsl.pipex.com>
From: Marco Atzeri <marco DOT atzeri AT gmail DOT com>
Message-ID: <af68eaaa-eb14-4f6a-911f-6d5a09a98e74@gmail.com>
Date: Wed, 22 Mar 2017 07:16:24 +0100
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On 22/03/2017 00:06, Martin O'Shea wrote:
> Hello
>
> I am using a 64 bit GCC compiler in NetBeans to compile a series of C
> programs which use the GMP multiple precision library to calculate numbers
> with varying lengths of zeroes. The programs are called from a shell script
> run from NetBeans or using Cygwin on Windows.
>

>
> The Windows PC concerned has 8Gb memory and according to the following piece
> of C code, the 64 bit version of Cygwin has 2Gb memory available:
>
>     #include <stdio.h>
>     #include <stdlib.h>
>
>     int main(int argc, char** argv) {
>
>         unsigned int bit = 0x40000000, sum = 0;
>         char *x;
>
>         while (bit > 4096) {
>             x = malloc(bit);
>             if (x)
>                 sum += bit;
>             bit >>= 1;
>         }
>         printf("%08x bytes (%.1fMb)\n", sum, sum / 1024.0 / 1024.0);
>
>         return (EXIT_SUCCESS);
>     }
>
> Given that the programs run without fault in Unix, I am assuming that there
> must be an environmental issue concerning memory when running the programs
> on Windows. Therefore, can anyone suggest if there is a way to increase
> memory to the GCC compiler within NetBeans or for the project I have, or to
> use `makefile` options to increase memory?
>
> I am using version 5.4.0 of GCC as given below:
>
>     $ gcc -v
>     Using built-in specs.
>     COLLECT_GCC=gcc
>     COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/5.4.0/lto-wrapper.exe
>     Target: x86_64-pc-cygwin
>
> I also do not understand why the memory checker program returns 2Gb.

2Gb is the largest block available.
As you never use free you have reserved ~ 4Gb


> Thanks
>
> Martin O'Shea.

Regards
Marco

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