Re: [nft PATH 10/16] libnftables: get rid of printf

[Phil Sutter <phil@nwl.cc>]

On Wed, Aug 16, 2017 at 10:43:04PM +0200, Eric Leblond wrote:
[...]
> diff --git a/include/nftables.h b/include/nftables.h
> index 348fbb0..ddff5d8 100644
> --- a/include/nftables.h
> +++ b/include/nftables.h
> @@ -30,6 +30,8 @@ struct output_ctx {
>  	unsigned int ip2name;
>  	unsigned int handle;
>  	unsigned int echo;
> +	void *ctx;
> +	int (*print)(void *ctx, const char *format, ...);
>  };

My compiler says:

| libnftables.c: In function 'nft_context_new':
| libnftables.c:113:20: warning: assignment left-hand side might be a candidate for a format attribute [-Wsuggest-attribute=format]
|   ctx->output.print = nft_print;
|                     ^

Not really a warning IMO, though.

Abstracting the topic a bit, maybe all these foo_print() callbacks
should die eventually and be replaced by formatters for different output
types, similar to nftnl_foo_snprintf() functions. Maybe the whole output
formatting actually even belongs to the application and libnftables has
to provide a way to extract object information. Not sure how much
knowlege the application should (need to) have about internal data
structures like e.g., struct table or struct expr.

Cheers, Phil