Re: [RFC] ethdev: convert string initialization

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

On Thu, Aug 01, 2024 at 02:27:22AM -0700, Ferruh Yigit wrote:
> gcc 15 experimental [1], with -Wextra flag, gives warning in variable
> initialization as string [2].
> 
> The warning has a point when initialized variable is intended to use as
> string, since assignment is missing the required null terminator for
> this case. But warning is useless for our usecase.
> 
> I don't know if this behaviour will change in gcc15, as it is still
> under development. But if not we may need to update our initialization.

i investigated this when msvc had some issues with it as well. we
determined that it is actually iso c standard compliant.

what basically happens is the characters of the string are copied up to
the destination size and any remaining characters from the string
literal (including the NUL) are discarded and that is what leads to
the warning.

yes, the copied bytes lost their NUL terminator but the destination
isn't a string so meh, whatever.

either way i support your fix, it deals with the problem with msvc as
well.

thank you!

> 
> In this patch only updated a few instance to show the issue, there are
> many instances to fix, if we prefer to go this way.
> Other option is to disable warning but it can be useful for actual
> string usecases, so I prefer to keep it.
> 
> [1]
> gcc (GCC) 15.0.0 20240801 (experimental)
> 
> [2]
> ../lib/ethdev/rte_flow.h:906:36:
>   error: initializer-string for array of ???unsigned char??? is too long
>         [-Werror=unterminated-string-initialization]
> 906 |         .hdr.dst_addr.addr_bytes = "\xff\xff\xff\xff\xff\xff",
>     |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> ../lib/ethdev/rte_flow.h:907:36:
>   error: initializer-string for array of ???unsigned char??? is too long
>          [-Werror=unterminated-string-initialization]
> 907 |         .hdr.src_addr.addr_bytes = "\xff\xff\xff\xff\xff\xff",
>     |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> ../lib/ethdev/rte_flow.h:1009:25:
>   error: initializer-string for array of ???unsigned char??? is too long
>          [-Werror=unterminated-string-initialization]
> 1009 |                         "\xff\xff\xff\xff\xff\xff\xff\xff"
>      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> ../lib/ethdev/rte_flow.h:1012:25:
>   error: initializer-string for array of ???unsigned char??? is too long
>          [-Werror=unterminated-string-initialization]
> 1012 |                         "\xff\xff\xff\xff\xff\xff\xff\xff"
>      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> ../lib/ethdev/rte_flow.h:1135:20:
>   error: initializer-string for array of ???unsigned char??? is too long
>          [-Werror=unterminated-string-initialization]
> 1135 |         .hdr.vni = "\xff\xff\xff",
>      |                    ^~~~~~~~~~~~~~
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@amd.com>
> ---
>  lib/ethdev/rte_flow.h | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
> index f864578f806b..8b623974cd44 100644
> --- a/lib/ethdev/rte_flow.h
> +++ b/lib/ethdev/rte_flow.h
> @@ -903,8 +903,8 @@ struct rte_flow_item_eth {
>  /** Default mask for RTE_FLOW_ITEM_TYPE_ETH. */
>  #ifndef __cplusplus
>  static const struct rte_flow_item_eth rte_flow_item_eth_mask = {
> -	.hdr.dst_addr.addr_bytes = "\xff\xff\xff\xff\xff\xff",
> -	.hdr.src_addr.addr_bytes = "\xff\xff\xff\xff\xff\xff",
> +	.hdr.dst_addr.addr_bytes = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
> +	.hdr.src_addr.addr_bytes = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
>  	.hdr.ether_type = RTE_BE16(0x0000),
>  };
>  #endif
> @@ -1005,12 +1005,10 @@ struct rte_flow_item_ipv6 {
>  #ifndef __cplusplus
>  static const struct rte_flow_item_ipv6 rte_flow_item_ipv6_mask = {
>  	.hdr = {
> -		.src_addr =
> -			"\xff\xff\xff\xff\xff\xff\xff\xff"
> -			"\xff\xff\xff\xff\xff\xff\xff\xff",
> -		.dst_addr =
> -			"\xff\xff\xff\xff\xff\xff\xff\xff"
> -			"\xff\xff\xff\xff\xff\xff\xff\xff",
> +		.src_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
> +			      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
> +		.dst_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
> +			      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
>  	},
>  };
>  #endif
> @@ -1132,7 +1130,7 @@ struct rte_flow_item_vxlan {
>  /** Default mask for RTE_FLOW_ITEM_TYPE_VXLAN. */
>  #ifndef __cplusplus
>  static const struct rte_flow_item_vxlan rte_flow_item_vxlan_mask = {
> -	.hdr.vni = "\xff\xff\xff",
> +	.hdr.vni = { 0xff, 0xff, 0xff },
>  };
>  #endif
>  
> -- 
> 2.43.0