Use temporary rule-local variables in GNU Make

Disclaimer: this is not well tested by me. For example, I didn't read about defered and parse-time variable-evaluation yet.

Idea from http://stackoverflow.com/questions/1909188/define-make-variable-at-rule-execution-time.

The problem

• I want to use local variable(s) throughout different statements in the same rule.
• The variable should not exist outside the rule.

Possible solution

Use an intermediate rule (or split up a rule in variable-init- and worker-parts):

    .PHONY = use_2_vars
        
    use_2_vars: FOO = foo
    use_2_vars: BAR = $(shell echo bar)
    use_2_vars: _use_2_vars
        
    _use_2_vars:
        @echo $(FOO)
        @echo $(BAR)
        
    print:
        @echo $(FOO)
        @echo $(BAR)

Things to note:

• use 1 variable-definition per line
• 'user-named' rule (use_2_vars) depends on a worker-rule (_use_2_vars); any actual work is done in the latter

Testing this:

    $ gmake use_2_vars
    foo
    bar
    $ gmake print
        
        
    $ 

I.o.w. both variables are set when the corresponding rule is executed, an are not set otherwise.