makefile - GNU Make using $(eval ...) not working -

here makefile:

libdirs       += ./librelease libdirs       += ./sharedarcgis/depfileslinux64/libreleaselinux64/skia libdirs       += ./sharedarcgis/depfileslinux64/libreleaselinux64/libtess libdirs       += ./sharedarcgis/depfileslinux64/libreleaselinux64/sqlite statics       = $(wildcard $(libdirs:=/*.a)) targeta       = libruntimecorejava.a targetd       = libruntimecorejava.so targetd1      = $(targetd).1 targetd2      = $(targetd).1.0 targetd3      = $(targetd).1.0.0 ar            = ar cqs ar_extract    = ar -x link          = g++ symlink       = ln -f -s ldflags       = -shared -wl,-soname,libruntimecorejava.so extract       =  : $(targetd) $(targeta)  $(targetd) : clean         mkdir -p ./obj ./librelease         $(foreach lib, $(statics), cp $(lib) ./obj;)         $(eval extract := $(wildcard ./obj/*.a))         echo $(extract)         $(foreach lib, $(extract), $(ar_extract) $(lib);)         $(foreach lib, $(extract), rm -f $(lib);)          #$(cxx) $(ldflags) $(objs)         #$(symlink) $(targetd) $(targetd1)         #$(symlink) $(targetd) $(targetd2)         #$(symlink) $(targetd) $(targetd3)  $(targeta) :         $(eval objs:=$(wildcard ./obj/*.o))         echo $(objs)         #$(ar) $(targeta) $(objs)  clean :         rm -rf ./ob 

here output:

[matt6809@hogganz400 arcgis2]$ ls -l ./obj total 23332 -rw-rw-r-- 1 matt6809 matt6809  191324 mar  7 09:18 libcommon.a -rw-rw-r-- 1 matt6809 matt6809 8427134 mar  7 09:18 libgeometryxlib.a -rw-rw-r-- 1 matt6809 matt6809   88580 mar  7 09:18 liblibtess.a -rw-rw-r-- 1 matt6809 matt6809 3401554 mar  7 09:18 libmapping.a -rw-rw-r-- 1 matt6809 matt6809 3558746 mar  7 09:18 libpe_s.a -rw-rw-r-- 1 matt6809 matt6809  412634 mar  7 09:18 libpe++_s.a -rw-rw-r-- 1 matt6809 matt6809  597808 mar  7 09:18 libsg_s.a -rw-rw-r-- 1 matt6809 matt6809 3523726 mar  7 09:18 libskia.a -rw-rw-r-- 1 matt6809 matt6809  730064 mar  7 09:18 libsqlite.a -rw-rw-r-- 1 matt6809 matt6809  814234 mar  7 09:18 libsymboldictionary.a -rw-rw-r-- 1 matt6809 matt6809 2128742 mar  7 09:18 libsymbolxlib.a [matt6809@hogganz400 arcgis2]$ make rm -rf ./obj mkdir -p ./obj ./librelease cp ./librelease/libcommon.a ./obj;  cp ./librelease/libgeometryxlib.a ./obj;  cp ./librelease/libmapping.a ./obj;  cp ./librelease/libpe_s.a ./obj;  cp ./librelease/libpe++_s.a ./obj;  cp ./librelease/libsg_s.a ./obj;  cp ./librelease/libsymboldictionary.a ./obj;  cp ./librelease/libsymbolxlib.a ./obj;  cp ./sharedarcgis/depfileslinux64/libreleaselinux64/skia/libskia.a ./obj;  cp ./sharedarcgis/depfileslinux64/libreleaselinux64/libtess/liblibtess.a ./obj;  cp ./sharedarcgis/depfileslinux64/libreleaselinux64/sqlite/libsqlite.a ./obj; echo   #g++ -shared -wl,-soname,libruntimecorejava.so  #ln -f -s libruntimecorejava.so libruntimecorejava.so.1 #ln -f -s libruntimecorejava.so libruntimecorejava.so.1.0 #ln -f -s libruntimecorejava.so libruntimecorejava.so.1.0.0 echo   #ar cqs libruntimecorejava.a  

why extract empty? output show libs copied on .obj file.

each command line in rule considered 'recipe', , each recipe invoke new instance of shell run. thus, when set value extract in 1 recipe, , try read in another, reading 2 different shell instances, , value not carry between them. 1 way around join commands single recipe so:

$(targetd) : clean         mkdir -p ./obj ./librelease;  \         lib in $(statics) do; cp $$lib ./obj; done; \         extract=`ls ./obj/*.a`; echo $$extract; \         lib in $$extract do; $(ar_extract) $$lib done; \         lib in $$extract do; rm -f $$lib; done; \ 

thus, when set extract, available commands within recipe.

see http://www.gnu.org/software/make/manual/make.html#recipes more info