Makefile findstring won't match numerical character - makefile

Question

CLANG_MAJOR_VER = x`${CXX} --version | egrep -i 'clang' | awk '{print $$3}' | awk '{ gsub(/\./, " "); print $$1 }'`xx
PAT = x6
CLANG_NAME = `${CXX} --version | grep -i 'clang' | awk '{print $$1}'`
CLANG_DEF = $(if $(findstring $(PAT),$(CLANG_MAJOR_VER)),abc,def)
all:
#echo $(CLANG_MAJOR_VER)
#echo $(CLANG_NAME)
#echo $(CLANG_DEF)
Result :
x6xx
clang
and if PAT is x or xx, then $(CLANG_DEF) will be abc, if PAT = 6, x6, 6x then $(CLANG_DEF) is def.

Answer 1

Your use of backticks would be fine in a shell script but it is not in a Makefile. The recursive assignments (VAR = VALUE) assign the exact right-hand-side strings to your variables and make expands them recursively when they are needed and only then, that is, in your case, when make expands the recipe of your all rule, just before passing it to the shell. So, if PAT = x6, when CLANG_DEF is expanded you have (decomposed in successive steps):
#echo $(CLANG_DEF)
#echo $(if $(findstring $(PAT),$(CLANG_MAJOR_VER)),abc,def)
#echo $(if $(findstring x6,x`${CXX} --version | egrep -i 'clang' | awk '{print $$3}' | awk '{ gsub(/\./, " "); print $$1 }'`xx),abc,def)
#echo $(if $(findstring x6,x`clang --version | egrep -i 'clang' | awk '{print $3}' | awk '{ gsub(/\./, " "); print $1 }'`xx),abc,def)
#echo $(if ,abc,def)
#echo def
And this does not depend on the result of the evaluation by the shell of:
clang --version | egrep -i 'clang' | awk '{print $3}' | awk '{ gsub(/\./, " "); print $1 }'
because it is not evaluated by the shell, it is only considered as a string by make when expanding $(findstring...)...
But if PAT = x, the recursive expansion becomes:
#echo $(CLANG_DEF)
#echo $(if $(findstring $(PAT),$(CLANG_MAJOR_VER)),abc,def)
#echo $(if $(findstring x,x`${CXX} --version | egrep -i 'clang' | awk '{print $$3}' | awk '{ gsub(/\./, " "); print $$1 }'`xx),abc,def)
#echo $(if $(findstring x,x`clang --version | egrep -i 'clang' | awk '{print $3}' | awk '{ gsub(/\./, " "); print $1 }'`xx),abc,def)
#echo $(if x,abc,def)
#echo abc
Instead of this unusual use of backsticks you could try to use the $(shell...) make function:
CLANG_MAJOR_VER = x$(shell ${CXX} --version | egrep -i 'clang' | awk '{print $$3}' | awk '{ gsub(/\./, " "); print $$1 }')xx
PAT = x6
CLANG_NAME = $(shell ${CXX} --version | grep -i 'clang' | awk '{print $$1}')
CLANG_DEF = $(if $(findstring $(PAT),$(CLANG_MAJOR_VER)),abc,def)
all:
#echo $(CLANG_MAJOR_VER)
#echo $(CLANG_NAME)
#echo $(CLANG_DEF)
And, by the way, your way of retrieving the version major number is not very robust (indeed, it fails on my Mac OS). Something like:
clang --version | sed -n '/version/s/.*version \([0-9]\+\).*/\1/p'
may be a bit better (not %100 sure, tested only on two OSes and two clang versions).

Answer 2

There is a library which can dissect simple (glob) string expressions:
include gmtt/gmtt.mk
define clang--version =
clang version 3.18.240-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
endef
parsed-string = $(call glob-match,$(clang--version),clang version *.*.*-* *Target: *Thread model: *InstalledDir: *)
$(info $(parsed-string))
$(info Major: $(word 2,$(parsed-string)) Minor: $(word 4,$(parsed-string)) Bugfix: $(word 6,$(parsed-string)))
Output:
clang§version§ 3 . 18 . 240 - 2ubuntu4 § (tags/RELEASE_380/final) Target:§ x86_64-pc-linux-gnu Thread§model:§ posix InstalledDir:§ /usr/bin
Major: 3 Minor: 18 Bugfix: 240