How to do if condition inside foreach in Makefile - makefile

Question

In Makefile, the pupose is to find a match in a list
#to find the $VER_X which is latest to $MY_VERSION but not greater than $MY_VERSION
VER_1 := 50.0.56.8
VER_2 := 50.0.56.17
VER_3 := 50.0.90.0
#in this case, VER_2 should be the match one
MY_VERSION := 50.0.56.19
I write a function which works fine to compare version string such as a.b.c.d
# function - compare version such as a.b.c.d
version_greater_equal = $(shell if printf '%s\n%s\n' '$(2)' '$(1)' | sort -Ct. -k1,1n -k2,2n -k3,3n -k4,4n ; then echo YES; else echo NO; fi)
The pupose is to find a match which is latest to ${MY_VERSION}
Solution-A and it works.
#solution-A: enumerate via ifeq
#this works, but it is not good idea for a larget number of VER_X
ifeq (YES,$(call version_greater_equal,${MY_VERSION},${VER_1}))
MATCH_ENU=${VER_1}
endif
ifeq (YES,$(call version_greater_equal,${MY_VERSION},${VER_2}))
MATCH_ENU=${VER_2}
endif
ifeq (YES,$(call version_greater_equal,${MY_VERSION},${VER_3}))
MATCH_ENU=${VER_3}
endif
Soluton-B , which doesn't work. How can I fix it?
#solution-2: loop (foreach)
VER_LIST := 50.0.56.8 50.0.56.17 50.0.90.0 50.1.42.3
MATCH_2 := $(foreach each, $(VER_LIST), $(if $(call version_greater_equal,${MY_VERSION},${each})=YES , ${each}))
The log
-->enumerate
MATCH_ENU = 50.0.56.17
-->enumerate
MATCH_2 = 50.0.56.8 50.0.56.17 50.0.90.0 50.1.42.3

Answer 1

Define a new function, which returns the second argument if it's greater-or-equal, or nothing.
version_greater_equal = $(shell if printf '%s\n%s\n' '$(2)' '$(1)' | sort -Ct. -k1,1n -k2,2n -k3,3n -k4,4n ; then echo $(2); fi)
Make a (sorted) list of versions:
VERS := $(VER_1) $(VER_2) $(VER_3) ...
Sift out the one greater than $(MY_VERSION):
LOW_VERS := $(foreach X,$(VERS),$(call version_greater_equal,${MY_VERSION},$(X)))
Take the last (and therefore greatest) of these:
MATCH_ENU := $(lastword $(LOW_VERS))
EDIT: Your Question seemed to imply that the versions would be listed in order (and your Solution A depends on it). But if you want a solution that works without that assumption, here goes.
I will not give a recursive function that returns just the largest value, because recursive functions give me vertigo. And besides, the advice #MadScientist gives me usually contains some horrible trap. So here's a purely iterative solution:
greater = ... function that returns the greater of the two arguments, you write it.
define reduce
X := $(call greater, $(wordlist 1,2,$(X))) $(wordlist 3,$(words $(X)), $(X))
endef
X := $(LOW_VERS)
$(foreach z, $(LOW_VERS), $(eval $(call reduce)))
Now X will contain the version you want.
P.S. Come to think of it, if we're making calls to the shell sort, it's probably easier just to sort the version list that way.