Re: [PATCH v3 1/3] mk: clear up libm and librt linkage confusion

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/10/2016 1:15 PM, Panu Matilainen wrote:
> There are two places that need -lm (test app and librte_sched) and
> exactly one that needs -lrt (librte_sched). Add the relevant
> DT_NEEDED entries to both, and eliminate the bogus discrepancy
> between Linux and BSD EXECENV_LDLIBS wrt these libs.
> 
> Signed-off-by: Panu Matilainen <pmatilai@redhat.com>
> ---
>  app/test/Makefile                | 2 ++
>  lib/librte_sched/Makefile        | 3 +++
>  mk/exec-env/linuxapp/rte.vars.mk | 2 +-
>  mk/rte.app.mk                    | 6 ++----
>  4 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/app/test/Makefile b/app/test/Makefile
> index ec33e1a..00e4df2 100644
> --- a/app/test/Makefile
> +++ b/app/test/Makefile
> @@ -160,6 +160,8 @@ CFLAGS += $(WERROR_FLAGS)
>  
>  CFLAGS += -D_GNU_SOURCE
>  
> +LDLIBS += -lm
> +
>  # Disable VTA for memcpy test
>  ifeq ($(CC), gcc)
>  ifeq ($(shell test $(GCC_VERSION) -ge 44 && echo 1), 1)
> diff --git a/lib/librte_sched/Makefile b/lib/librte_sched/Makefile
> index b1cb285..4d631f6 100644
> --- a/lib/librte_sched/Makefile
> +++ b/lib/librte_sched/Makefile
> @@ -41,6 +41,9 @@ CFLAGS += $(WERROR_FLAGS)
>  
>  CFLAGS_rte_red.o := -D_GNU_SOURCE
>  
> +LDLIBS += -lm
> +LDLIBS += -lrt
> +
>  EXPORT_MAP := rte_sched_version.map
>  
>  LIBABIVER := 1
> diff --git a/mk/exec-env/linuxapp/rte.vars.mk b/mk/exec-env/linuxapp/rte.vars.mk
> index 5fd7d85..d51bd17 100644
> --- a/mk/exec-env/linuxapp/rte.vars.mk
> +++ b/mk/exec-env/linuxapp/rte.vars.mk
> @@ -48,7 +48,7 @@ endif
>  # Workaround lack of DT_NEEDED entry
>  EXECENV_LDFLAGS = --no-as-needed
>  
> -EXECENV_LDLIBS  = -lrt -lm
> +EXECENV_LDLIBS  =
>  EXECENV_ASFLAGS =
>  
>  ifeq ($(CONFIG_RTE_BUILD_SHARED_LIB),y)
> diff --git a/mk/rte.app.mk b/mk/rte.app.mk
> index daac09f..cadc7ab 100644
> --- a/mk/rte.app.mk
> +++ b/mk/rte.app.mk
> @@ -77,11 +77,7 @@ _LDLIBS-$(CONFIG_RTE_LIBRTE_LPM)            += -lrte_lpm
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_POWER)          += -lrte_power
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_ACL)            += -lrte_acl
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_METER)          += -lrte_meter
> -
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_SCHED)          += -lrte_sched
> -_LDLIBS-$(CONFIG_RTE_LIBRTE_SCHED)          += -lm
> -_LDLIBS-$(CONFIG_RTE_LIBRTE_SCHED)          += -lrt
> -
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_VHOST)          += -lrte_vhost
>  
>  ifeq ($(CONFIG_RTE_LIBRTE_VHOST_NUMA),y)
> @@ -104,6 +100,8 @@ _LDLIBS-$(CONFIG_RTE_LIBRTE_PMD_XENVIRT)    += -lxenstore
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_MPIPE_PMD)      += -lgxio
>  # QAT PMD has a dependency on libcrypto (from openssl) for calculating HMAC precomputes
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_PMD_QAT)        += -lcrypto
> +_LDLIBS-$(CONFIG_RTE_LIBRTE_SCHED)          += -lm
> +_LDLIBS-$(CONFIG_RTE_LIBRTE_SCHED)          += -lrt
>  endif # !CONFIG_RTE_BUILD_SHARED_LIBS
>  
>  _LDLIBS-y += --start-group
> 
This is causing a shared library compilation error with gcc:

"
== Build app/test-acl
  LD testacl
/root/dpdk/build/lib/librte_meter.so: error: undefined reference to 'ceil'
collect2: error: ld returned 1 exit status
"

There is an indirect libm dependency from test-acl. Adding -lm fixes the
issue.

But this issue not seen by everybody, not sure why I am getting this but
not others.

Also clang compiles fine, only fails with gcc.
I am using Fedora 23, gcc version:
gcc (GCC) 5.3.1 20151207 (Red Hat 5.3.1-2)

I will dig some more.

Regards,
ferruh