Re: [dpdk-dev] [PATCH v3 01/33] meson: add libatomic as a global dependency for i686 clang

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>-----Original Message-----
>From: dev <dev-bounces@dpdk.org> On Behalf Of Bruce Richardson
>Sent: Monday, March 30, 2020 6:47 PM
>To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
>Cc: Thomas Monjalon <thomas@monjalon.net>; Pavan Nikhilesh
>Bhagavatula <pbhagavatula@marvell.com>; Liang Ma
><liang.j.ma@intel.com>; Peter Mccarthy <peter.mccarthy@intel.com>;
>Marko Kovacevic <marko.kovacevic@intel.com>; Ori Kam
><orika@mellanox.com>; Radu Nicolau <radu.nicolau@intel.com>; Akhil
>Goyal <akhil.goyal@nxp.com>; Tomasz Kantecki
><tomasz.kantecki@intel.com>; Sunil Kumar Kori <skori@marvell.com>;
>David Hunt <david.hunt@intel.com>; Honnappa Nagarahalli
><honnappa.nagarahalli@arm.com>; dev@dpdk.org;
>david.marchand@redhat.com; mattias.ronnblom@ericsson.com
>Subject: Re: [dpdk-dev] [PATCH v3 01/33] meson: add libatomic as a
>global dependency for i686 clang
>
>On Sun, Mar 29, 2020 at 08:13:10PM +0530, jerinj@marvell.com wrote:
>> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>>
>> Add libatomic as a global dependency when compiling for 32-bit using
>> clang. As we need libatomic for 64-bit atomic ops.
>>
>> Cc: bruce.richardson@intel.com
>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> ---
>>  config/meson.build                  | 10 ++++++++++
>>  drivers/event/octeontx/meson.build  |  5 -----
>>  drivers/event/octeontx2/meson.build |  5 -----
>>  drivers/event/opdl/meson.build      |  5 -----
>>  examples/l2fwd-event/meson.build    |  5 -----
>>  lib/librte_distributor/meson.build  |  5 -----
>>  lib/librte_rcu/meson.build          |  5 -----
>>  7 files changed, 10 insertions(+), 30 deletions(-)
>>
>> diff --git a/config/meson.build b/config/meson.build
>> index abedd76f2..6e5530110 100644
>> --- a/config/meson.build
>> +++ b/config/meson.build
>> @@ -173,6 +173,16 @@ if pcap_dep.found() and
>cc.has_header('pcap.h', dependencies: pcap_dep)
>>  	dpdk_extra_ldflags += '-lpcap'
>>  endif
>>
>> +
>> +# for clang 32-bit compiles we need libatomic for 64-bit atomic ops
>> +if cc.get_id() == 'clang' and dpdk_conf.get('RTE_ARCH_64') == false
>> +	atomic_dep = cc.find_library('atomic', required: true)
>> +	if atomic_dep.found()
>> +		add_project_link_arguments('-latomic', language: 'c')
>> +		dpdk_extra_ldflags += '-latomic'
>> +	endif
>> +endif
>> +
>
>Minor nit, you don't need to check for .found(), since the configure will
>fail if it's not found, since "required" is set to true.

Yup but I felt a bit odd adding the dependency without using .found().
I will remove the inner if check in the next version.

>
>For cleanliness, you may also be able to use get_pkgconfig_variable() or
>get_configtool_variable() to get -latomic, rather than hard-coding it,
>though in this case I suspect hard-coding is fine.

Looks like get_pkgconfig_variable/get_configtool_variable only work on dependency
object using it on object from find_library() causes meson to error out 
` Unknown method "get_pkgconfig_variable" in object `

>
>With the superfluous if removed
>
>Acked-by: Bruce Richardson <bruce.richardson@intel.com>