array taking more input than definition

Asked Mar 18 '13 at 11:45

Active Mar 18 '13 at 12:07

Viewed 64 times

 #include <stdio.h>
 int main(void)
 {
    int n,i;
    scanf("%d",&n);
    int a[n];
    for(i=0;i<n;i++)
    {
        a[i]=i;
    printf("%d",a[i]);

    }
    for(i=0;i<n+1;i++)
    {
        a[i]=i;
        printf("%d",a[i]);

    }       
    return 0;   
 }

here if we give any input eg 5 then output is... 01234012345 here question is that code should give an error but insted it prints 5 which is stored in a[5] & a[5] is undeclared

edited Mar 18 '13 at 12:07

Jens

69,818
15
125
179

asked Mar 18 '13 at 11:45

SID_J

4

C lets you shoot yourself in the foot. In other words there's no automatic bounds checking. – cnicutar Mar 18 '13 at 11:46
2

Can you declare dynamically sized arrays on the stack in C? – Nick Mar 18 '13 at 11:46
2

It's _undefined behavior_. – Some programmer dude Mar 18 '13 at 11:46
@Nick They are called VLAs. – cnicutar Mar 18 '13 at 11:46
@Nick It's called [variable length array](http://en.wikipedia.org/wiki/Variable-length_array) and allowed since the C99 standard. – Some programmer dude Mar 18 '13 at 11:47
@cnicutar thanks. not sure I like the look of them! – Nick Mar 18 '13 at 11:48
Where does the memory get allocated? or that implementation dependent? – Nick Mar 18 '13 at 11:48
@Nick On the stack. But the standard doesn't say anything about the stack.. so yeah. – cnicutar Mar 18 '13 at 11:49
I look forward to the day when a C implementation chooses to use a graph, instead of a stack. This is the day that everyone talking about a "stack" will feel very foolish. – autistic Mar 18 '13 at 11:54

array taking more input than definition

0 Answers0