How to force an error in a gnumake file

Question

I want to detect a condition in my makefile where a tool is the wrong version and force the make to fail with an error message indicating the item is not the right version.<

Answer 1

From the manual:

$(error Bad svn version v1.4, please install v1.6)

This will result make to a fatal error:

$ make
Makefile:2: *** Bad svn version v1.4, please install v1.6.  Stop.

Answer 2

While $(error... works, sometimes its easier to use a rule that fails

test_svn_version:
        @if [ $$(svn --version --quiet | \
                perl -ne '@a=split(/\./); \
                          print $$a[0]*10000 + $$a[1]*100 + $$a[2]') \
              -lt 10600 ]; \
        then \
            echo >&2 "Svn version $$(svn --version --quiet) too old; upgrade to v1.6";
            false; \
        fi

Then you make test_svn_version a prerequisite of your top level target.

Answer 3

The conditional needs some attention too.

ifeq ($(shell svnversion --version | sed s/[^0-9\.]*://), 1.4) 
    $(error Bad svnversion v1.4, please install v1.6)
endif