Re: [dpdk-dev] [PATCH 1/2] config/arm: avoid variable reuse

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

> -----Original Message-----
> From: Dharmik Thakkar <Dharmik.Thakkar@arm.com>
> Sent: Friday, September 18, 2020 7:27 AM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: thomas@monjalon.net; dev@dpdk.org; nd <nd@arm.com>
> Subject: Re: [dpdk-dev] [PATCH 1/2] config/arm: avoid variable reuse
> 
> 
> 
> > On Sep 17, 2020, at 4:33 AM, Juraj Linkeš <juraj.linkes@pantheon.tech> wrote:
> >
> >
> >
> >> -----Original Message-----
> >> From: dev <dev-bounces@dpdk.org> On Behalf Of Dharmik Thakkar
> >> Sent: Tuesday, August 25, 2020 11:13 PM
> >> To: Thomas Monjalon <thomas@monjalon.net>
> >> Cc: dev@dpdk.org; nd@arm.com; Dharmik Thakkar
> >> <dharmik.thakkar@arm.com>
> >> Subject: [dpdk-dev] [PATCH 1/2] config/arm: avoid variable reuse
> >>
> >> Rename 'machine' to 'machine_properties' in config/arm/meson.build
> >> since 'machine' is previously being used in config/meson.build
> >>
> >
> > Wasn't the same variable name used by design? That is update the variable
> according to what's in config/arm/meson.build so that the new updated variable
> would be used in config/meson.build after that?
> >
> 
> The variable ‘machine’ within config/arm/meson.build is essentially machine +
> properties, so I think it makes sense to use a different variable name.
> Also, since, ‘machine’ is a configuration option, IMO it is incorrect to update it.
> 

It is a configuration option defined by us and only used in the config folder, so I guess the original author didn't think much of overwriting. It is actually used in the same manner in both config/meson.build and config/arm/meson.build and that is to set RTE_MACHINE, so I'd say it makes sense to use the same variable name from this point of view.

Also, I see that it's being overwritten in the code (although only for a special case):
if machine == 'default'
	if host_machine.cpu_family().startswith('x86')
		# matches the old pre-meson build systems default
		machine = 'corei7'

But it is only being overwritten in this special case and I think there is value in preserving the original configuration value. That leads me to the conclusion that using the same name was not a deliberate design choice (which was my original question). So, +1 from me.

> >> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> >> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> >> ---
> >> config/arm/meson.build | 18 +++++++++---------
> >> 1 file changed, 9 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> >> 8728051d5e38..e89ecdc4ccd2 100644
> >> --- a/config/arm/meson.build
> >> +++ b/config/arm/meson.build
> >> @@ -141,12 +141,12 @@ else
> >> 	dpdk_conf.set('RTE_CACHE_LINE_SIZE', 128)
> >> 	dpdk_conf.set('RTE_ARCH_ARM64', 1)
> >>
> >> -	machine = []
> >> +	machine_properties = []
> >> 	cmd_generic = ['generic', '', '', 'default', '']
> >> 	cmd_output = cmd_generic # Set generic by default
> >> 	machine_args = [] # Clear previous machine args
> >> 	if arm_force_default_march and not meson.is_cross_build()
> >> -		machine = impl_generic
> >> +		machine_properties = impl_generic
> >> 		impl_pn = 'default'
> >> 	elif not meson.is_cross_build()
> >> 		# The script returns ['Implementer', 'Variant', 'Architecture', @@
> >> -158,9 +158,9 @@ else
> >> 			cmd_output = cmd.stdout().to_lower().strip().split(' ')
> >> 		endif
> >> 		# Set to generic if variable is not found
> >> -		machine = get_variable('impl_' + cmd_output[0], ['generic'])
> >> -		if machine[0] == 'generic'
> >> -			machine = impl_generic
> >> +		machine_properties = get_variable('impl_' + cmd_output[0],
> >> ['generic'])
> >> +		if machine_properties[0] == 'generic'
> >> +			machine_properties = impl_generic
> >> 			cmd_output = cmd_generic
> >> 		endif
> >> 		impl_pn = cmd_output[3]
> >> @@ -170,7 +170,7 @@ else
> >> 	else
> >> 		impl_id = meson.get_cross_property('implementor_id',
> >> 'generic')
> >> 		impl_pn = meson.get_cross_property('implementor_pn',
> >> 'default')
> >> -		machine = get_variable('impl_' + impl_id)
> >> +		machine_properties = get_variable('impl_' + impl_id)
> >> 	endif
> >>
> >> 	# Apply Common Defaults. These settings may be overwritten by
> >> machine @@ -181,14 +181,14 @@ else
> >> 		endif
> >> 	endforeach
> >>
> >> -	message('Implementer : ' + machine[0])
> >> -	foreach flag: machine[1]
> >> +	message('Implementer : ' + machine_properties[0])
> >> +	foreach flag: machine_properties[1]
> >> 		if flag.length() > 0
> >> 			dpdk_conf.set(flag[0], flag[1])
> >> 		endif
> >> 	endforeach
> >>
> >> -	foreach marg: machine[2]
> >> +	foreach marg: machine_properties[2]
> >> 		if marg[0] == impl_pn
> >> 			foreach flag: marg[1]
> >> 				if cc.has_argument(flag)
> >> --
> >> 2.17.1
> >>
> >
> >

Reviewed-by: Juraj Linkeš <juraj.linkes@pantheon.tech>