Re: [dpdk-dev] [PATCH] meter: provide experimental alias of API for old apps

[Thomas Monjalon <thomas@monjalon.net>]

I think the title should be about ABI, not API.

13/05/2020 14:11, Ferruh Yigit:
> Duplicate the existing and versioned symbol as experimental.

Would be good to explain the case of the meter lib you are addressing.
If I understand well, you consider we "broke" the experimental ABI
during 20.02 when moving symbols from EXPERIMENTAL to DPDK_20.0.1
(and to DPDK_21 during 20.05).
That's why you want to add back the EXPERIMENTAL symbol as an alias
of the symbol in the next ABI (21).


> This is to prevent DPDK maturing experimental API breaking old
> applications using that experimental API.
> The relevant process update is captured in:
> https://patches.dpdk.org/patch/65863/
> 
> Created VERSION_SYMBOL_EXPERIMENTAL helper macro.
> 
> Updated the 'check-experimental-syms.sh' buildtool, which was
> complaining that the symbol is in EXPERIMENTAL tag in .map file but it
> is not in the .experimental section (__rte_experimental tag is missing).
> Updated tool in a way it won't complain if the symbol in the
> EXPERIMENTAL tag duplicated in some other block in .map file (versioned)
> 
> Enabled function versioning for meson build for the library.
> 
> Fixes: 30512af820fe ("meter: remove experimental flag from RFC4115 trTCM API")

Even if it's never backported, it would be more correct to add Cc: stable
to indicate it is fixing previous release (20.02 here).


> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
[...]
> --- a/lib/librte_meter/rte_meter_version.map
> +++ b/lib/librte_meter/rte_meter_version.map
> @@ -20,4 +20,12 @@ DPDK_21 {
>  	rte_meter_trtcm_rfc4115_color_blind_check;
>  	rte_meter_trtcm_rfc4115_config;
>  	rte_meter_trtcm_rfc4115_profile_config;
> +
>  } DPDK_20.0;
> +
> +EXPERIMENTAL {
> +       global:
> +
> +	rte_meter_trtcm_rfc4115_config;
> +	rte_meter_trtcm_rfc4115_profile_config;
> +};
>