How do you force a makefile to rebuild a target

Question

I have a makefile that builds and then calls another makefile. Since this makefile calls more makefiles that does the work it doesnt really change. Thus it keeps thinking the project is built and upto date.

dnetdev11 ~ # make
make: `release' is up to date.

How do i force the makefile to rebuild the target?

clean = $(MAKE) -f ~/xxx/xxx_compile.workspace.mak clean


build = svn up ~/xxx                                                       \
        $(clean)                                                                \
        ~/cbp2mak/cbp2mak -C ~/xxx ~/xxx/xxx_compile.workspace        \
        $(MAKE) -f ~/xxx/xxx_compile.workspace.mak $(1)                    \


release:
        $(build )

debug:
        $(build DEBUG=1)

clean:
        $(clean)

install:
        cp ~/xxx/source/xxx_utility/release/xxx_util /usr/local/bin
        cp ~/xxx/source/xxx_utility/release/xxxcore.so /usr/local/lib

Note: Names removed to protect the innocent

Edit: Final Fixed version:

clean = $(MAKE) -f xxx_compile.workspace.mak clean;


build = svn up;                                         \
        $(clean)                                        \
        ./cbp2mak/cbp2mak -C . xxx_compile.workspace;   \
        $(MAKE) -f xxx_compile.workspace.mak    $(1);   \


.PHONY: release debug clean install

release:
        $(call build,)

debug:
        $(call build,DEBUG=1)

clean:
        $(clean)

install:
        cp ./source/xxx_utillity/release/xxx_util /usr/bin
        cp ./dlls/Release/xxxcore.so /usr/lib

Answer 1

You could declare one or more of your targets to be phony: http://www.gnu.org/software/automake/manual/make/Phony-Targets.html

Answer 2

If I recall correctly, 'make' uses timestamps (file modification time) to determine whether or not a target is up to date. A common way to force a re-build is to update that timestamp, using the 'touch' command. You could try invoking 'touch' in your makefile to update the timestamp of one of the targets (perhaps one of those sub-makefiles), which might force Make to execute that command.

Answer 3

Someone else suggested .PHONY which is definitely correct. .PHONY should be used prior to any rule for which a date comparison between the input and the output is invalid. Since you don't have any targets of the form output: input you should use .PHONY for ALL of them!

All that said, you probably should define some variables at the top of your makefile for the various filenames, and define real make rules that have both input and output sections so you can use the benefits of make, namely that you'll only actually compile things that are necessary to copmile!

Edit: added example. Untested, but this is how you do .PHONY

.PHONY: clean    
clean:
    $(clean)

Answer 4

The -B switch to make, which is also --also-make tells make to disregard timestamps and make the specified targets. This may defeat the purpose of using make, but it may be what you need.

Answer 5

One trick that used to be documented in a Sun manual for make is to use a (non-existent) target '.FORCE'. You could do this by creating a file, force.mk, that contains:

.FORCE:
$(FORCE_DEPS): .FORCE

Then, assuming your existing makefile is called makefile, you could run:

make FORCE_DEPS=release -f force.mk -f makefile release

Since .FORCE does not exist, anything that depends on it will be out of date and rebuilt.

All this will work with any version of make; on Linux, you have GNU Make and can therefore use the .PHONY target as discussed.

It is also worth considering why make considers release to be up to date. This could be because you have a touch release command in amongst the commands executed; it could be because there is a file or directory called 'release' that exists and has no dependencies and so is up to date. Then there's the actual reason...