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Re: define variable in rule
From: |
John Graham-Cumming |
Subject: |
Re: define variable in rule |
Date: |
Wed, 08 Jun 2005 13:42:18 -0400 |
On Wed, 2005-06-08 at 23:54 +0800, address@hidden wrote:
> Can the variable be defined in rule ? Like this:
>
> 1 target : $(OBJ_FILE)
> 2 TMP_LIB := $(shell cat $(OBJ_FILES))
> 3 $(LD) $(OPT_LD_STD) $(LDFLAGS) -o $@ $(TMP_LIB)
> $(EXTERNAL_LIBS) $(SYSTEM_LIBS)
>
> The OBJ_FILE is a text file with .o file list, and I want to translate
> it to .o list used as the argument of link, so the variable TMP_LIB is
> defined.
>
> But when do Make, syntax error found in line 3. So I doubt the variable
> can not be defined within a fule.
Not like that it can't, but you could do this:
target: TMP_LIB := $(shell cat $(OBJ_FILES))
target:
$(LD) $(OPT_LD_STD) $(LDFLAGS) -o $@ $(TMP_LIB) \
$(EXTERNAL_LIBS) $(SYSTEM_LIBS)
(This has the side effect of defining TMP_LIB for any of target's
prerequisites.)
OTOH I don't see any real need for that TMP_LIB variable here (unless
it's being referenced in one of the other variables on the $(LD)
command-line) and so you could simplify your life greatly and just do:
target:
$(LD) $(OPT_LD_STD) $(LDFLAGS) -o $@ $(shell cat $(OBJ_FILES)) \
$(EXTERNAL_LIBS) $(SYSTEM_LIBS)
If you do that then you don't even need to bother with the $(shell)
because you could just use backticks and do
target:
$(LD) $(OPT_LD_STD) $(LDFLAGS) -o $@ `cat $(OBJ_FILES)` \
$(EXTERNAL_LIBS) $(SYSTEM_LIBS)
John.
--
John Graham-Cumming
Home: http://www.jgc.org/
Work: http://www.electric-cloud.com/
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GNU Make Standard Library: http://gmsl.sf.net/