use of "=" or ":=" operators defining variables in Makefiles (expanding SUBLANG)
Laura Arjona Reina <[email protected]>
| Newsgroups | gmane.linux.debian.devel.www |
|---|---|
| Message-ID | <[email protected]> |
Dear all I'm having a look at different Makefiles of the Debian website, to see how the Chinese variants are being taken into account to generate several pages. I've seen a common pattern: if SUBLANG is not defined, the target is usually file.$(LANGUAGE).html (e.g. index.es.html), but if SUBLANG is defined, we need to expand the SUBLANG variable and then we'll have multiple targets to be built with the corresponding rule (e.g. index.zh-cn.html index.zh-tw.html index.zh-hk.html). My question is about the lines defining the variable that will contain the target(s): in some Makefiles the "=" operator is used, and in others, the operator ":=" is used. Specifically, see the exact lines (I grepped SUBLANG and removed the not relevant lines from the output): english/security/Makefile:22:DSARDF := $(sort $(foreach i,$(SUBLANG),$(subst dsa,dsa.$(LANGUAGE)-$(i),dsa.rdf))) english/security/Makefile:23:DSALONGRDF := $(sort $(foreach i,$(SUBLANG),$(subst dsa-long,dsa-long.$(LANGUAGE)-$(i),dsa-long.rdf))) english/security/Makefile:24:DSAALLRDF := $(sort $(foreach i,$(SUBLANG),$(subst dsa-all,dsa-all.$(LANGUAGE)-$(i),dsa-all.rdf))) english/News/weekly/Makefile:27: HTMLFILES := $(foreach i, $(SUBLANG), \ english/News/weekly/Makefile:29: HTMLDESTFILES := $(foreach i, $(SUBLANG), \ english/News/Makefile:22:NEWSRDF := $(sort $(foreach i,$(SUBLANG),$(subst news,news.$(LANGUAGE)-$(i),news.rdf))) english/devel/website/stats/Makefile:20:STATS = $(sort $(foreach i,$(SUBLANG),\ english/Makefile:24:SITEMAP = $(sort $(foreach i,$(SUBLANG),\ english/Makefile:27:SEARCHXML = $(sort $(foreach i,$(SUBLANG),$(subst search,search.$(LANGUAGE)-$(i),search.xml))) chinese/Make.lang:5:SUBLANG := cn hk tw Makefile.common:47:HTMLFILES = $(sort $(foreach i,$(SUBLANG),\ Makefile.common:49:HTMLDESTFILES = $(sort $(foreach i,$(SUBLANG),\ For what I've read in https://www.gnu.org/software/make/manual/make.html#Flavors and https://www.gnu.org/software/make/manual/make.html#Using-Variables (thanks friends for the pointers), I *think* that ":=" should be used everywhere for these SUBLANG expansions, but I don't know if, for example, would penalize in performance. In any case, I'd like to know if there is a particular reason for declaring these SUBLANG-affected targets differently (using different operator) in different places in the website. Best regards -- Laura Arjona Reina https://wiki.debian.org/LauraArjona