Re: [PATCH v2] lib/cryptodev: fix assertion to remove GCC compilation warning

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 22 May 2023 15:04:52 -0400
Kamil Godzwon <kamilx.godzwon@intel.com> wrote:

> /home/vagrant/dpdk/build/include/rte_crypto_sym.h:1009:4: \
> warning: Value stored to 'left' is never read [deadcode.DeadStores]
>                           left = 0;
>                           ^      ~
>   1 warning generated.
> 
> Compilator sees that the variable 'left' is never read after
> assignment a '0' value. To get rid of this warning message, use 'if'
> condition to verify the 'left' value before RTE_ASSERT.
> 
> Signed-off-by: Kamil Godzwon <kamilx.godzwon@intel.com>
> ---
> v2:
> Changed commit message as the line was too long
> Removed braces
> ---
>  lib/cryptodev/rte_crypto_sym.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/cryptodev/rte_crypto_sym.h b/lib/cryptodev/rte_crypto_sym.h
> index b43174dbec..dcef1a5049 100644
> --- a/lib/cryptodev/rte_crypto_sym.h
> +++ b/lib/cryptodev/rte_crypto_sym.h
> @@ -1016,7 +1016,9 @@ rte_crypto_mbuf_to_vec(const struct rte_mbuf *mb, uint32_t ofs, uint32_t len,
>  		left -= seglen;
>  	}
>  
> -	RTE_ASSERT(left == 0);
> +	if (left != 0)
> +		RTE_ASSERT(false);
> +
>  	return i;
>  }
>  

This could happen if the passed in length to this routine was larger than
the amount of data in the mbuf. Should the function check and return an error?

Panic should only be reserved for seriously corrupted input (like invalid mbuf).

Also, this is a big enough function that it really should not be inlined.