Date: Fri, 10 Jun 2005 15:40:58 -0700 From: Mike Hunter <mhunter@ack.berkeley.edu> To: freebsd-hackers@freebsd.org Subject: unitialized memory is all zeros...why not garbage instead? Message-ID: <20050610224058.GA11336@malcolm.berkeley.edu>
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Hey everybody,
I have a feeling that I'm missing something really obvious, but I'm having
trouble understanding why the following program:
#include <stdlib.h>
#include <stdio.h>
int main (int argc, char * argv[])
{
void * ptr = malloc(65536);
size_t i;
for (i = 0; i < 65536; i++)
{
printf ("%x", *((unsigned char *)ptr + i));
if ((i % 16) == 0)
{
puts("\n");
}
}
return 0;
}
Never prints anything but "0"'s.
I ran less up to my hw.physmem by feeding it /dev/random and watching
top, and then ran the program, so I "know" there was tons of non-zero
bits in memory.
I'm curious because I am worried about information leaks between processes
on the same machine...did somebody decide to solve this problem while I
wasn't paying attention? :)
%gcc -v
Using built-in specs.
Configured with: FreeBSD/i386 system compiler
Thread model: posix
gcc version 3.4.2 [FreeBSD] 20040728
%uname -a
FreeBSD mylabtop.berkeley.edu 5.4-STABLE FreeBSD 5.4-STABLE #1: Wed May
11 12:05:39 PDT 2005
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