Re: [PATCH nft 1/2] utils: add memory_allocation_check() helper

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Nov 08, 2023 at 07:24:24PM +0100, Thomas Haller wrote:
> libnftables kills the process on out of memory (xmalloc()), so
> when we use libraries that propagate ENOMEM to libnftables, we
> also abort the process.
> 
> For example:
> 
>      nlr = nftnl_rule_alloc();
>      if (!nlr)
>           memory_allocation_error();
> 
> Add memory_allocation_check() macro which can simplify this common
> check to:
> 
>      nlr = memory_allocation_check(nftnl_rule_alloc());
> 
> Signed-off-by: Thomas Haller <thaller@redhat.com>
> ---
>  include/utils.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/utils.h b/include/utils.h
> index 36a28f893667..fcd7c598fe9f 100644
> --- a/include/utils.h
> +++ b/include/utils.h
> @@ -142,6 +142,16 @@ extern void __memory_allocation_error(const char *filename, uint32_t line) __nor
>  #define memory_allocation_error()		\
>  	__memory_allocation_error(__FILE__, __LINE__);
>  
> +#define memory_allocation_check(cmd)               \
> +	({                                         \
> +		typeof((cmd)) _v = (cmd);          \
> +		const void *const _v2 = _v;        \
> +                                                   \
> +		if (!_v2)                          \

please don't hide a if branch inside a macro.

> +			memory_allocation_error(); \
> +		_v;                                \
> +	})
> +
>  extern void xfree(const void *ptr);
>  extern void *xmalloc(size_t size);
>  extern void *xmalloc_array(size_t nmemb, size_t size);
> -- 
> 2.41.0
>