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

Panu Matilainen pmatilai at redhat.com
Tue Mar 15 07:24:09 CET 2016


On 03/14/2016 06:44 PM, Ferruh Yigit wrote:
> 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 at 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.

Right, librte_meter indeed has a dependency on libm that I've missed.
The curious thing is why is it not failing everywhere - I cannot 
reproduce that at all on Fedora 23. Poking around in math.h leads to 
bits/mathlinline.h where the answer probably lies: ceil() is typically 
provided by inline code, but for one reason or another that is not 
available in your setup.

Anyway, I'll send a patch to add the missing dependency, thanks for 
spotting and reporting!

	- Panu -

> Regards,
> ferruh
>
>
>
>



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