[ovs-dev] [PATCH 2/2] acinclude: Use AC_SEARCH_LIBS for linking with dl.

Ilya Maximets i.maximets at samsung.com
Thu Feb 21 13:54:39 UTC 2019


On 21.02.2019 16:48, Flavio Leitner wrote:
> On Tue, Feb 19, 2019 at 10:12:28AM +0300, Ilya Maximets wrote:
>> DPDK uses dlopen to load plugins and we need to search for
>> library containing this function. But we should not do this
>> in a loop because 'AC_SEARCH_LIBS' could do this for us.
>> Also, 'AC_SEARCH_LIBS' prints user-visible messages that are
>> useful for debuging.
>> Also added the new 'checking' message and code normalized to
>> be more readable.
>>
>> With this change we'll have following additional messages:
> 
> 
> I think -ldl is only needed if MLX PMDs are enabled, right?

Unfortunately, not. It's used in 'eal_plugins_init()' inside
lib/librte_eal/common/eal_common_options.c.
And it's not guarded by any CONFIG. So, we have to look for library
with 'dlopen' in any configuration.

> After this patch a library providing dlopen becomes mandatory, then
> embedded folks might not like this new dependency.
> 
> Otherwise the patch looks good to me.
> fbl
> 
>>
>>   checking for library containing dlopen... -ldl
>>   checking whether linking with dpdk works... yes
>>
>> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
>> ---
>>  acinclude.m4 | 50 +++++++++++++++++++++-----------------------------
>>  1 file changed, 21 insertions(+), 29 deletions(-)
>>
>> diff --git a/acinclude.m4 b/acinclude.m4
>> index 2bb82b9c2..e4aed4690 100644
>> --- a/acinclude.m4
>> +++ b/acinclude.m4
>> @@ -294,36 +294,28 @@ AC_DEFUN([OVS_CHECK_DPDK], [
>>        ], [[#include <rte_config.h>]])
>>      ], [], [[#include <rte_config.h>]])
>>  
>> -    # On some systems we have to add -ldl to link with dpdk
>> -    #
>> -    # This code, at first, tries to link without -ldl (""),
>> -    # then adds it and tries again.
>> -    # Before each attempt the search cache must be unset,
>> -    # otherwise autoconf will stick with the old result
>> +    # DPDK uses dlopen to load plugins.
>> +    OVS_FIND_DEPENDENCY([dlopen], [dl], [libdl])
>> +
>> +    AC_MSG_CHECKING([whether linking with dpdk works])
>> +    LIBS="$DPDK_LIB $LIBS"
>> +    AC_LINK_IFELSE(
>> +      [AC_LANG_PROGRAM([#include <rte_config.h>
>> +                        #include <rte_eal.h>],
>> +                       [int rte_argc; char ** rte_argv;
>> +                        rte_eal_init(rte_argc, rte_argv);])],
>> +      [AC_MSG_RESULT([yes])
>> +       DPDKLIB_FOUND=true],
>> +      [AC_MSG_RESULT([no])
>> +       if test "$DPDK_AUTO_DISCOVER" = "true"; then
>> +         AC_MSG_ERROR(m4_normalize([
>> +            Could not find DPDK library in default search path, Use --with-dpdk
>> +            to specify the DPDK library installed in non-standard location]))
>> +       else
>> +         AC_MSG_ERROR([Could not find DPDK libraries in $DPDK_LIB_DIR])
>> +       fi
>> +      ])
>>  
>> -    DPDKLIB_FOUND=false
>> -    save_LIBS=$LIBS
>> -    for extras in "" "-ldl"; do
>> -        LIBS="$DPDK_LIB $extras $save_LIBS"
>> -        AC_LINK_IFELSE(
>> -           [AC_LANG_PROGRAM([#include <rte_config.h>
>> -                             #include <rte_eal.h>],
>> -                            [int rte_argc; char ** rte_argv;
>> -                             rte_eal_init(rte_argc, rte_argv);])],
>> -           [DPDKLIB_FOUND=true])
>> -        if $DPDKLIB_FOUND; then
>> -            break
>> -        fi
>> -    done
>> -
>> -    # If linking unsuccessful
>> -    if test "$DPDKLIB_FOUND" = "false" ; then
>> -      if $DPDK_AUTO_DISCOVER; then
>> -        AC_MSG_ERROR([Could not find DPDK library in default search path, Use --with-dpdk to specify the DPDK library installed in non-standard location])
>> -      else
>> -        AC_MSG_ERROR([Could not find DPDK libraries in $DPDK_LIB_DIR])
>> -      fi
>> -    fi
>>      CFLAGS="$ovs_save_CFLAGS"
>>      LDFLAGS="$ovs_save_LDFLAGS"
>>      if test "$DPDK_AUTO_DISCOVER" = "false"; then
>> -- 
>> 2.17.1
>>
>> _______________________________________________
>> dev mailing list
>> dev at openvswitch.org
>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> 
> 
> 


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