Re: Why doesn't this code generate an inaccessible memory-error?

From:

Francis Glassborow <francis.glassborow@btinternet.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Sat, 6 Feb 2010 05:30:44 CST

Message-ID:

<XMOdnfrxpLttufDWnZ2dnUVZ8s2dnZ2d@bt.com>

iminsik@gmail.com wrote:

It was supposed that this code would generate an inaccessible memory-
error. I compiled this code and ran the compiled executable by g++ in
Ubuntu 9.10; it didn't generate any error. However, when it was
compiled by gcc in Windows, it generated an error expected. Can you
explain the difference between the two?

Simply that there is no requirement in C++ that an implementation detect
such problems, not least because it cannot always be detected with any
level of certainty.

I note that, on closer examination the problem is NOT inaccessible
memory but a complete mess.
Exactly what do you think
*(arri + i) = j;
does?

j is an int and *(arri + i) is?

In addition, why are you using malloc in C++. It is not wrong, just
unusual and leads to that cast. Indeed your code IS pure C and therefore
has very little to do with C++

# include <stdio.h>
# include <stdlib.h>

# define LIMIT 10000

int main(void)
{
     int i=0, j=0;
     int * arri = (int *) malloc(sizeof(int)*(LIMIT-LIMIT/2));
     for (i=0, j=LIMIT;i<LIMIT;++i,--j)
     {
         *(arri+i)=j;
     }
     free(arri);
     return 0;
}

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