Re: [dpdk-dev] [PATCH] mk: fix lib filtering

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2017-04-06 16:14, Olivier Matz:
> I get the following error when linking the test application:
>   build/lib/librte_pmd_thunderx_nicvf.a(nicvf_hw.o):
>   In function `nicvf_qsize_regbit':
>   drivers/net/thunderx/base/nicvf_hw.c:451: undefined reference to `log2'
>   build/lib/librte_pmd_thunderx_nicvf.a(nicvf_hw.o):
>   In function `nicvf_rss_reta_update':
>   drivers/net/thunderx/base/nicvf_hw.c:804: undefined reference to `log2'
>   build/lib/librte_pmd_thunderx_nicvf.a(nicvf_hw.o):
>   In function `nicvf_rss_reta_query':
>   drivers/net/thunderx/base/nicvf_hw.c:825: undefined reference to `log2'
> 
> While I don't know why it does not happen for a default build, the error
> can be explained. The link command line is:
> 
>    gcc -o test ... *.o ... -Wl,-lm ... -Wl,-lrte_pmd_thunderx_nicvf ...
> 
> rte_pmd_thunderx_nicvf needs the math library, and it should be
> added after. This is not the case because the test application also
> adds the math library.
> 
> The makefile already filters the libraries, but it keeps the first
> occurrence of the lib. Instead, the last one should be kept.
> 
> Fixes: edf4d331dcdb ("mk: eliminate duplicates from libraries list")
> 
> Cc: stable@dpdk.org
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>

Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>

It is a really nice Makefile recursive function :)

> +# all the words except the first one
> +allbutfirst = $(wordlist 2,$(words $(1)),$(1))
> +
> +# Eliminate duplicates without sorting, only keep the last occurrence
> +filter-libs = \
> +	$(if $(1),$(strip\
> +		$(if \
> +			$(and \
> +				$(filter $(firstword $(1)),$(call allbutfirst,$(1))),\
> +				$(filter -l%,$(firstword $(1)))),\
> +			,\
> +			$(firstword $(1))) \
> +		$(call filter-libs,$(call allbutfirst,$(1)))))
> +
> +LDLIBS := $(call filter-libs,$(LDLIBS))

Applied, thanks