Re: [Valgrind-users] memory check on the stack

[Nicholas N. <nj...@ca...>]

On Wed, 14 Jan 2004, S=E9bastien de Menten wrote:

> #define N 16
> main()
> {
>   int a[N];
>   //    int *a =3D new int[N];
>   int i;
>   for(i=3D0; i<=3DN+10; i++)
>      a[i] =3D 0;
>   return (0);
> }
>
> The error message is cryptic:
> =3D=3D5749=3D=3D Jump to the invalid address stated on the next line
> =3D=3D5749=3D=3D    at 0x0: ???
> =3D=3D5749=3D=3D  Address 0x0 is not stack'd, malloc'd or free'd
>
> If I change the line
>   for(i=3D0; i<=3DN+10; i++)
> by
>   for(i=3D0; i<=3DN; i++)
> it does not detect the error.
>
> If I allocate the memory dynamically,i.e.
>   // int a[N];
>   int *a =3D new int[N];
> Valgrind detects correctly the error.
>
> Does it mean that valgrind is unable to check the stack allocated memory =
?

That's right.  The cryptic error message is occurring because the array
overrun would be clobbering the return address on the stack, so when the
function returns it tries to jump to 0x0.

N