On 6/9/2016 11:10 AM, Thomas Monjalon wrote:

Hi Ferruh,

2016-05-27 17:48, Ferruh Yigit:

quoted

Replace --no-as-needed linker flag with --as-needed flag, which will
only link libraries directly called by application. This requires inter
library dependencies resolved correctly.

Not linking all libraries cause a compile error for lpcap and possible
to have other similar compiler errors, so increasing the scope of
--start-group argument.

What is the error?

This is with -as-needed flag, and static library compilation:

.../dpdk/build/lib/librte_pmd_pcap.a(rte_eth_pcap.o): In function
`eth_dev_stop':
rte_eth_pcap.c:(.text+0xcc1): undefined reference to `pcap_dump_close'
rte_eth_pcap.c:(.text+0xcd6): undefined reference to `pcap_close'
rte_eth_pcap.c:(.text+0xd19): undefined reference to `pcap_close'
rte_eth_pcap.c:(.text+0xd58): undefined reference to `pcap_close'
/root/development/dpdk/build/lib/librte_pmd_pcap.a(rte_eth_pcap.o): In
function `open_tx_pcap':
rte_eth_pcap.c:(.text+0x190b): undefined reference to `pcap_open_dead'
rte_eth_pcap.c:(.text+0x191b): undefined reference to `pcap_dump_open'
...

pcap pmd has libpcap calls, but while linking final application
(testpmd), linker is not able to find objects that has these.

The command line for compilation is:
gcc ... -o test ... -Wl,--whole-archive <dpdk libs> -Wl,-lpcap
-Wl,--start-group <more dpdk libs> -Wl,-lrte_pmd_pcap <more dpdk libs>
-Wl,--end-group -Wl,--no-whole-archive

-lpcap is provided, but since before -lrte_pmd_pcap, references not
resolved.

Previously, with "-no-as-needed" flag, all shared libraries linked
always, which was preventing compile error.

quoted

cmdline_test application causes compile error because of cyclic
dependency between librte_eal <-> librte_mempool. A workaround added to
cmdline_test for compile error.

Signed-off-by: Ferruh Yigit <redacted>

quoted

--- a/app/cmdline_test/Makefile
+++ b/app/cmdline_test/Makefile

@@ -46,6 +46,7 @@ SRCS-y += commands.c
 
 CFLAGS += -O3
 CFLAGS += $(WERROR_FLAGS)

A comment is required here to explain the workaround.

Sure, I will add a comment and send a new version of the patch.

quoted

+LDFLAGS += -no-as-needed

The option should be --no-as-needed.

Right

quoted

--- a/mk/exec-env/linuxapp/rte.vars.mk
+++ b/mk/exec-env/linuxapp/rte.vars.mk

@@ -46,7 +46,7 @@ EXECENV_CFLAGS  = -pthread
 endif
 
 # Workaround lack of DT_NEEDED entry

This comment is obsolete now.

Will remove.

quoted

-EXECENV_LDFLAGS = --no-as-needed
+EXECENV_LDFLAGS = --as-needed

Why put this option for Linux only?

When this option not defined at all, different compilers behave
different, some has --as-needed as default and cause compilation issues,
I guess that is why for Linux --no-as-needed is forces. I assume BSD
compilers by default use --no-as-needed, so we don't have any
compilation problem.
And it looks like there is no specific reason to not force BSD to
--as-needed, I will test it.

Shouldn't we restrict this option to app.mk only?

Having --no-needed flag only for app should be OK. Let me test first,
and as a result should we move this to app.mk?

quoted

--- a/mk/rte.app.mk
+++ b/mk/rte.app.mk

@@ -58,6 +58,7 @@ _LDLIBS-y += -L$(RTE_SDK_BIN)/lib
 #
 
 _LDLIBS-y += --whole-archive
+_LDLIBS-y += --start-group

--start-group must be used only to solve circular dependencies.
Ideally we should not use it. I think it's needed only because
of EAL logs using mempool (must be removed).

No, this is not the reason, please check above lpcap compile error, that
is the reason of this update.

Why extending it?
I'm afraid we are masking some issues.

But if we have a convention to add external libraries after dpdk
libraries, that also should solve this issue, but that is more update
than just updating --start-group.

quoted

 _LDLIBS-$(CONFIG_RTE_LIBRTE_DISTRIBUTOR)    += -lrte_distributor
 _LDLIBS-$(CONFIG_RTE_LIBRTE_REORDER)        += -lrte_reorder

@@ -111,8 +112,6 @@ _LDLIBS-y                                   += -lcrypto
 endif
 endif # !CONFIG_RTE_BUILD_SHARED_LIBS
 
-_LDLIBS-y += --start-group
-
 _LDLIBS-$(CONFIG_RTE_LIBRTE_KVARGS)         += -lrte_kvargs
 _LDLIBS-$(CONFIG_RTE_LIBRTE_MBUF)           += -lrte_mbuf
 _LDLIBS-$(CONFIG_RTE_LIBRTE_IP_FRAG)        += -lrte_ip_frag