问题
In a makefile, I'd like to define a variable specifying whether the current redhat-release is greater than 5.3. (This variable will be passed to gcc as a #define)
So far I've come up with:
# Find out which version of Red-Hat we're running
RH_VER_NUM = $(shell /bin/grep -o [0-9].[0-9] /etc/redhat-release)
RH_GT_5_3 = $RH_VER_NUM > '5.3'
What would be the correct way to define RH_GT_5_3?
回答1:
GNU Make doesn't contain any string comparisons other than equality, and test can only do less-than/greater-than tests on integers. Split the version number into its integral parts and do the comparison that way. Try this (note also that := is better than = here, as make's lazy evaluation would call your $(shell) commands many more times than required:
RH_VER_MAJOR := $(shell echo $(RH_VER_NUM) | cut -f1 -d.)
RH_VER_MINOR := $(shell echo $(RH_VER_NUM) | cut -f2 -d.)
RH_GT_5_3 := $(shell [ $(RH_VER_MAJOR) -gt 5 -o \( $(RH_VER_MAJOR) -eq 5 -a $(RH_VER_MINOR) -ge 3 \) ] && echo true)
ifeq ($(RH_GT_5_3),true)
CPPFLAGS += -DRH_GT_5_3=1
endif
回答2:
A little bit shorter solution is:
RH_GT_5_3 := $(shell echo -e "5.4\n$(RH_VER_NUM)"|sort -ct. -k1,1n -k2,2n && echo YES)
This will set RH_GT_5_3 to "YES" if RH_VER_NUM is greater then or equal to 5.4 (so greater then 5.3). Otherwise RH_GT_5_3 will be set to empty.
If multiple version numbers need to be checked we can define a function:
IF_VER_GE = $(shell echo -e "$2\n$1"|sort -ct. -k1,1n -k2,2n && echo YES)
GLIBC := $(word 2,$(shell getconf GNU_LIBC_VERSION))
...
all:
ifeq "$(call IF_VER_GE, $(GLIBC), 2.5)" "YES"
echo "GE"
else
echo "LT"
endif
I used the "$(word 2,..." instead of "$(lastword,..." because the later does not work in make 3.8. And shorter...
... some aeons later
I tried to solve the version comparison with internal makefile functions. I found a project (GNU Make Standard Library (GMSL)), which adds an include to the makefile which implements integer arithmetic. Unfortunately with the common unary numeral system. But comparing version numbers are more complex. As I worked with versions having numbers greater then 100_000 I decided to implement a more general solution. It works with arbitrary number of subversion numbers each with arbitrary digits. Some ideas were borrowed from the GMSL project
It implements the ver.lt function. It returns 'T' if the first version number is less then the second. It returns an empty string otherwise. Of course, the subversion numbers are compared numerically not lexicographically. So 1.20 is greater then 1.3. There is some issues. 1.2 < 1.2.0, 1.0.1 < 1.00.1, 1.9.1 < 1.01.1 (as it is expected that a number starts with a nonzero digit. Except the 0 itself.). I do not want to solve them now.
The solution
It is testAed under gnu make 3.82.90. There are some very long lines as makefile add spaces if the '\' is used. I left some implemented, but not used functions in the code. Maybe I would use better temporary variable names (like GMSL uses _gmsl). Sometimes temporary variables could be left off, but the code would be more cryptic.
.SILENT:
S :=
SP := $S $S
# For non empty strings
#not = $(if $1,$S,T)
#str.ne = $(if $(subst $1,,$2),T,$S)
str.eq = $(if $(subst $1,,$2),$S,T)
str.le = $(call str.eq,$(word 1,$(sort $1 $2)),$1)
#str.ge = $(call str.eq,$(word 1,$(sort $1 $2)),$2)
# Creates a list of digits from a number
mklist = $(eval __tmp := $1)$(foreach i,0 1 2 3 4 5 6 7 8 9,$(eval __tmp := $$(subst $$i,$$i ,$(__tmp))))$(__tmp)
# reverse: $(subst $(SP),,$(list))
#pop = $(wordlist 2, $(words $1), x $1)
#push = $1 $2
shift = $(wordlist 2, $(words $1), $1)
#unshift = $2 $1
num.le = $(eval __tmp1 := $(call mklist,$1))$(eval __tmp2 := $(call mklist,$2))$(if $(call str.eq,$(words $(__tmp1)),$(words $(__tmp2))),$(call str.le,$1,$2),$(call str.le,$(words $(__tmp1)),$(words $(__tmp2))))
#num.ge = $(eval __tmp1 := $(call mklist,$1))$(eval __tmp2 := $(call mklist,$2))$(if $(call str.eq,$(words $(__tmp1)),$(words $(__tmp2))),$(call str.ge,$1,$2),$(call str.ge,$(words $(__tmp1)),$(words $(__tmp2))))
#Strip zeroes from the beginning of a list
list.strip = $(eval __flag := 1)$(foreach d,$1,$(if $(__flag),$(if $(subst 0,,$d),$(eval __flag :=)$d,$S),$d))
#Strip zeroes from the beginning of a number
#num.strip = $(subst $(SP),,$(call list.strip,$(call mklist,$1)))
# temp string: 0 - two number equals, L first LT, G first GT or second is short,
gen.cmpstr = $(eval __Tmp1 := $(subst ., ,$1))$(eval __Tmp2 := $(subst ., ,$2))$(foreach i,$(__Tmp1),$(eval j := $(word 1,$(__Tmp2)))$(if $j,$(if $(call str.eq,$i,$j),0,$(if $(call num.le,$i,$j),L,G)),G)$(eval __Tmp2 := $$(call shift,$(__Tmp2))))$(if $(__Tmp2), L)
ver.lt = $(call str.eq,$(word 1,$(call list.strip,$(call gen.cmpstr,$1,$2))),L)
all:
echo ver.lt,1.20,1.3:$(call ver.lt,1.20,1.3)%
echo ver.lt,1.5.9,1.5:$(call ver.lt,1.5.9,1.5)%
echo ver.lt,1.4.9,1.5:$(call ver.lt,1.4.9,1.5)%
echo ver.lt,1.2,1.2.0:$(call ver.lt,1.2,1.2.0)%
echo ver.lt,1.20.3.4.5,1.10.5:$(call ver.lt,1.20.3.4.5,1.10.5)%
echo ver.lt,1.20.3.4.5,1.0.5:$(call ver.lt,1.20.3.4.5,1.0.5)%
echo ver.lt,1.0,1.0.5:$(call ver.lt,1.0,1.0.5)%
echo ver.lt,1.20,1.10.3:$(call ver.lt,1.20,1.10.3)%
echo ver.lt,1.20,1.30.3::$(call ver.lt,1.20,1.30.3)%
echo ver.lt,1.10.3,1.10.3:$(call ver.lt,1.10.3,1.10.3)%
And the output
ver.lt,1.20,1.3:%
ver.lt,1.5.9,1.5:%
ver.lt,1.4.9,1.5:T%
ver.lt,1.2,1.2.0:T%
ver.lt,1.20.3.4.5,1.10.5:%
ver.lt,1.20.3.4.5,1.0.5:%
ver.lt,1.0,1.0.5:T%
ver.lt,1.20,1.10.3:%
ver.lt,1.20,1.30.3::T%
ver.lt,1.10.3,1.10.3:%
More music
I have found another interesting project called makepp (makepp.sourceforge.net). It enables to implement new functions in perl inside the makefile.
回答3:
The simplest solution I think of is by using bc:
# Find out which version of Red-Hat we're running
RH_VER_NUM = $(shell /bin/grep -o [0-9].[0-9] /etc/redhat-release)
RH_GT_5_3 = $(shell echo $(RH_VER_NUM)\>=5.3 | bc )
ifeq ($(RH_GT_5_3),1)
CPPFLAGS += -DRH_GT_5_3=1
endif
This will be equal to 1 if bigger than 5.3, and 0 otherwise.
回答4:
Kudos to TrueY for coming up with a version that doesn't use any expensive shell commands. I have a simpler version that only compares 2 small integers (often you only care about the major version).
The idea is simply
x > y
= y is member of {0,1,2,3,4 ..., x - 1)
The member of operator can be implemented with GNU make's $(filter) and generating the set can be done with $(wordlist)
# returns all integers less than x
LessThanSubset=$(wordlist 1,$(1),0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20)
# if x > y, return 1, empty otherwise
GreaterThan=$(if $(filter $(2),$(call LessThanSubset,$(1))),1)
GreaterOrEqual=$(if $(filter $(2),$(call LessThanSubset,$(1)) $(1)),1)
# example
$(error 5 > 4 = $(call GreaterThan,5,4))