Re: have a problem mixing Make and java.

[John Graham-Cumming]

richard t wrote:
> src = ./src
> obj = ./obj
> ui_c = com/rich/tool/ui/MainPanel.class
> db_c= com/rich/tool/db/Connect.class \
>           com/rich/tool/db/User.class
> tl_c =  com/rich/tool/Tool.class
>  
> classes = $(ui_c) $(db_c) $(tl_c)
>  
> target: $(classes)
>        echo "done"
>  
> $(classes) : $(subst .class,.java,$(subst
> $(obj),$(src),$(classes)))
>        javac $(JFLAGS) $(subst $(src)/,,$<)
>  
> ok the problem that I get is that the macro ($<) does
> not seem to iterate for the
> different source files and I would like to know why
> that happens, and also a problem is that when a source
> file gets changed Make doesnt seem to know that it
> needs to recompile the source for it and I would like
> to know why that is.

I think that the problem is that the $(classes) is constructed from 
$(ui_c) etc. and if you look at the definition of those then you'll see 
that none of them have $(obj)/ prepended and and hence the $(subst 
$(obj),$(src),$(classes)) in the prerequisite list of the $(classes) 
rule does nothing and hence the prerequisite list doesn't point into the 
./src directory.

I believe that explains the problems that you are seeing.  I think that 
defining classes like this will solve the problem:

    classes := $(addprefix $(obj)/,$(ui_c) $(db_c) $(tl_c))

Might be nice to have a sources variable as well:

    sources := $(classes:.class=.java)

Secondly your $(classes) : $(subst...) rule is wrong.  This says that 
each individual class file depends on every single source file.  I think 
what you mean to say is each class file depends on the corresponding 
source file.

The simplest way to do that is for you to define a pattern rule relating 
%.class and %.java files.   For example,

    $(obj)/%.class : $(src)/%.java
        javac $(JFLAGS) $<

(I wasn't clear why you were stripping $(src)/ from the names of source 
files fed to javac so I've not done that here, but you can easily modify 
this using $*).

Now one important difference with this and what I think you intended is 
that there will be a single invocation of javac for *each* .java file 
whereas I think you intended the classic javac with a list of .java 
files to compile.

GNU Make doesn't really have that as a concept since it generally works 
with a single input file to single output file.  You can fake this up, 
but I don't have time to write that up tonight :-)

John.
--
John Graham-Cumming
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