[dpdk-dev] efd: fix compilation by removing dep to libmath

  When we compile the dpdk with:
  CONFIG_RTE_LIBRTE_EFD=y
  CONFIG_RTE_LIBRTE_NFP_PMD=n
  CONFIG_RTE_LIBRTE_THUNDERX_NICVF_PMD=n
  CONFIG_RTE_LIBRTE_SCHED=n
  CONFIG_RTE_LIBRTE_METER=n

The linker gives the following error:
  lib/librte_efd.a(rte_efd.o): In function `rte_efd_create':
  lib/librte_efd/rte_efd.c:560: undefined reference to `log2'
  collect2: error: ld returned 1 exit status

This is because the '-lm' is missing in mk/rte.app.mk.

An alternative, which is proposed by this patch, is to use the compiler
builtin rte_bsf32() to process log2 instead of the libmath log2() that
requires to include math.h and link with -lm.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 lib/librte_efd/Makefile  | 2 --
 lib/librte_efd/rte_efd.c | 3 +--
 2 files changed, 1 insertion(+), 4 deletions(-)
  

> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Friday, January 27, 2017 2:23 PM
> To: dev@dpdk.org; Marohn, Byron; De Lara Guarch, Pablo
> Subject: [PATCH] efd: fix compilation by removing dep to libmath
> 
> When we compile the dpdk with:
>   CONFIG_RTE_LIBRTE_EFD=y
>   CONFIG_RTE_LIBRTE_NFP_PMD=n
>   CONFIG_RTE_LIBRTE_THUNDERX_NICVF_PMD=n
>   CONFIG_RTE_LIBRTE_SCHED=n
>   CONFIG_RTE_LIBRTE_METER=n
> 
> The linker gives the following error:
>   lib/librte_efd.a(rte_efd.o): In function `rte_efd_create':
>   lib/librte_efd/rte_efd.c:560: undefined reference to `log2'
>   collect2: error: ld returned 1 exit status
> 
> This is because the '-lm' is missing in mk/rte.app.mk.
> 
> An alternative, which is proposed by this patch, is to use the compiler
> builtin rte_bsf32() to process log2 instead of the libmath log2() that
> requires to include math.h and link with -lm.
> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>

Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>

Nice catch, thanks!
  

2017-01-27 14:45, De Lara Guarch, Pablo:
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> > 
> > When we compile the dpdk with:
> >   CONFIG_RTE_LIBRTE_EFD=y
> >   CONFIG_RTE_LIBRTE_NFP_PMD=n
> >   CONFIG_RTE_LIBRTE_THUNDERX_NICVF_PMD=n
> >   CONFIG_RTE_LIBRTE_SCHED=n
> >   CONFIG_RTE_LIBRTE_METER=n
> > 
> > The linker gives the following error:
> >   lib/librte_efd.a(rte_efd.o): In function `rte_efd_create':
> >   lib/librte_efd/rte_efd.c:560: undefined reference to `log2'
> >   collect2: error: ld returned 1 exit status
> > 
> > This is because the '-lm' is missing in mk/rte.app.mk.
> > 
> > An alternative, which is proposed by this patch, is to use the compiler
> > builtin rte_bsf32() to process log2 instead of the libmath log2() that
> > requires to include math.h and link with -lm.
> > 
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> 
> Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
> 
> Nice catch, thanks!

Fixes: 56b6ef874f80 ("efd: new Elastic Flow Distributor library")

Applied, thanks