variant length array?

[Robert P. J. Day]

On Tue, 5 Apr 2016, Wenda Ni wrote:

> Hi all,
>
> I come across the following code in a kernel module code. It defines
> an array whose length is variant at runtime, depending on the actual
> inputs. It seems that kernel compiler supports this, which is
> obvious an error in the standard ANSI C. Do I have the correct
> understanding on it?
>
> Thank you.
>
>
> u32 rxe_icrc_hdr(struct rxe_pkt_info *pkt, struct sk_buff *skb)
> {
>          ...
>          int hdr_size = sizeof(struct udphdr) +
>                  (skb->protocol == htons(ETH_P_IP) ?
>                  sizeof(struct iphdr) : sizeof(struct ipv6hdr));
>          u8 tmp[hdr_size + RXE_BTH_BYTES];
>          ...
> }

  pretty sure "sizeof" can be calculated at compile time so i don't
see a problem here.

rday


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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

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