On 03/24, Luca Boccassi wrote:
>On Sun, 2019-03-17 at 11:34 +0800, Ye Xiaolong wrote:
>> On 03/02, Ye Xiaolong wrote:
>> > > >  _LDLIBS-$(CONFIG_RTE_LIBRTE_PMD_AF_PACKET)  +=
>> > > > -lrte_pmd_af_packet
>> > > > +_LDLIBS-$(CONFIG_RTE_LIBRTE_PMD_AF_XDP)     +=
>> > > > -lrte_pmd_af_xdp
>> > > > -lelf -lbpf
>> > > 
>> > > Are symbols from libelf being used by the PMD?
>> > 
>> > Hmm, it is a leftover of RFC, libelf is no longer needed in this
>> > version, will
>> > remove it in next version.
>> > 
>> 
>> Correction, libelf is needed for libbpf, so we still need to keep
>> it. 
>
>If libbpf needs libelf for its internal usage, it should be linked
>against it itself. Unless symbols from libelf are used in static
>functions defined in libbpf's public headers. Is this the case?
>

Yes, that's the case. without the libelf, it would have build error as below,
and these symbols are used in static functions of libbpf.

/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_nextscn'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_rawdata'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_memory'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `gelf_getrel'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_strptr'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_end'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_getscn'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_begin'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `gelf_getsym'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_version'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `gelf_getehdr'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `elf_getdata'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libbpf.so: undefined reference to `gelf_getshdr'

Thanks,
Xiaolong
>-- 
>Kind regards,
>Luca Boccassi