Re: [RFC][v5][PATCH 8/8]: Define clone_with_pids() syscall

H. Peter Anvin
2009-09-09T15:58:19Z

On 09/09/2009 05:19 AM, Arnd Bergmann wrote:
>
> This is a complex problem. The structure above would need a conversion
> for the pointer size that you can avoid by using a u64, but that introduces
> another problem:
>
> 2. use a single pointer, with variable length data structures:
>
> struct pid_set {
> int num_pids;
> pid_t pids[0];
> };
>
> Since pid_t is always an int, you have no problem with padding or
> incompatible types, but rely on a data structure definition that
> is not in C89 (not sure about C99).
>

C90 has these data structures, but you have to give the array a nonzero
length:

struct pid_set {
int num_pids;
pid_t pids[1];
};

In C99, this is spelt:

struct pid_set {
int num_pids;
pid_t pids[];
};

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.