[dpdk-dev] [PATCH 1/3] mk: fix librte_pipeline dependency list truncation

[Panu Matilainen]

On 06/21/2016 01:01 PM, Dumitrescu, Cristian wrote:
>
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Panu Matilainen
>> Sent: Tuesday, June 21, 2016 9:12 AM
>> To: dev at dpdk.org
>> Cc: christian.ehrhardt at canonical.com; thomas.monjalon at 6wind.com
>> Subject: [dpdk-dev] [PATCH 1/3] mk: fix librte_pipeline dependency list
>> truncation
>>
>> In other libraries, dependency list is always appended to, but
>> in commit 6cbf4f75e059 it with an assignment. This causes the
>> librte_eal dependency added in commit 6cbf4f75e059 to get discarded,
>> resulting in missing dependency on librte_eal.
>>
>> Fixes: b3688bee81a8 ("pipeline: new packet framework logic")
>> Fixes: 6cbf4f75e059 ("mk: fix missing internal dependencies")
>>
>> Signed-off-by: Panu Matilainen <pmatilai at redhat.com>
>> ---
>>  lib/librte_pipeline/Makefile | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_pipeline/Makefile b/lib/librte_pipeline/Makefile
>> index 95387aa..a8f3128 100644
>> --- a/lib/librte_pipeline/Makefile
>> +++ b/lib/librte_pipeline/Makefile
>> @@ -53,7 +53,7 @@ SYMLINK-$(CONFIG_RTE_LIBRTE_PIPELINE)-include +=
>> rte_pipeline.h
>>
>>  # this lib depends upon:
>>  DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) += lib/librte_eal
>> -DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) := lib/librte_table
>> +DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) += lib/librte_table
>>  DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) += lib/librte_port
>>
>>  include $(RTE_SDK)/mk/rte.lib.mk
>> --
>> 2.5.5
>
>
> In release 16.4, EAL was missing from the dependency list, now it is added. The librte_pipeline uses rte_malloc, therefore it depends on librte_eal being present.
>
> In the Makefile of the other Packet Framework libraries (librte_port, librte_table), it looks like the first dependency in the list is EAL, which is listed with the assignment operator, followed by others that are listed with the append operator:
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_XYZ) := lib/librte_eal
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_XYZ) += lib/librte_some other lib
>
> Therefore, at least for cosmetic reasons, we should probably do the same in librte_pipeline, which requires changing both the librte_eal and the librte_table lines as below:
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) := lib/librte_eal
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) += lib/librte_table
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_PIPELINE) += lib/librte_port

Ah, didn't notice those because the assignment is first of the dependencies.

>
> However, some other libraries e.g. librte_lpm simply add the EAL dependency using the append operator:
> 	DEPDIRS-$(CONFIG_RTE_LIBRTE_LPM) += lib/librte_eal
>
> To be honest, I need to refresh my knowledge on make, I don't remember right now when we should use the assignment and when the append. Do we need to use the assign for first dependency (EAL) and append for others or should we use append everywhere?

At least in automake, you need to assign before you can append. But in 
gmake this apparently is not the case, quoting from 
https://www.gnu.org/software/make/manual/html_node/Appending.html:

"When the variable in question has not been defined before, ‘+=’ acts 
just like normal ‘=’: it defines a recursively-expanded variable. 
However, when there is a previous definition, exactly what ‘+=’ does 
depends on what flavor of variable you defined originally."

So there's no need to use := anywhere for the dependencies, in fact its 
probably best avoided to avoid issues like this. Of course after the 
third patch in this "series" is applied, mistakes like these can no 
longer go unnoticed.

	- Panu -

> Thanks,
> Cristian
>