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cond-undef-lint.mk revision 1.1 
      1 # $NetBSD: cond-undef-lint.mk,v 1.1 2020/09/14 06:44:50 rillig Exp $
      2 #
      3 # Tests for defined and undefined variables in .if conditions, in lint mode.
      4 #
      5 # As of 2020-09-14, lint mode contains experimental code for printing
      6 # accurate error messages in case of undefined variables, instead of the
      7 # wrong "Malformed condition".
      8 
      9 .MAKEFLAGS: -dL
     10 
     11 # DEF is defined, UNDEF is not.
     12 DEF=		defined
     13 
     14 # An expression based on a defined variable is fine.
     15 .if !${DEF}
     16 .  error
     17 .endif
     18 
     19 # Since the condition fails to evaluate, neither of the branches is taken.
     20 .if ${UNDEF}
     21 .  error
     22 .else
     23 .  error
     24 .endif
     25 
     26 # The variable name depends on the undefined variable, which is probably a
     27 # mistake.  The variable UNDEF, as used here, can be easily turned into
     28 # an expression that is always defined, using the :U modifier.
     29 #
     30 # The outer expression does not generate an error message since there was
     31 # already an error evaluating this variable's name.
     32 #
     33 # TODO: Suppress the error message "Variable VAR. is undefined".  That part
     34 # of the expression must not be evaluated at all.
     35 .if ${VAR.${UNDEF}}
     36 .  error
     37 .else
     38 .  error
     39 .endif
     40 
     41 # The variable VAR.defined is not defined and thus generates an error message.
     42 .if ${VAR.${DEF}}
     43 .  error
     44 .else
     45 .  error
     46 .endif
     47 
     48 
     49 # Variables that are referenced indirectly may be undefined in a condition.
     50 #
     51 # A practical example for this is CFLAGS, which consists of CWARNS, COPTS
     52 # and a few others.  Just because these nested variables are not defined,
     53 # this does not make the condition invalid.
     54 #
     55 # The crucial point is that at the point where the variable appears in the
     56 # condition, there is no way to influence the definedness of the nested
     57 # variables.  In particular, there is no modifier that would turn undefined
     58 # nested variables into empty strings, as an equivalent to the :U modifier.
     59 INDIRECT=	${NESTED_UNDEF} ${NESTED_DEF}
     60 NESTED_DEF=	nested-defined
     61 
     62 # Since NESTED_UNDEF is not controllable at this point, it must not generate
     63 # an error message.  This condition should generate no error message at all.
     64 #
     65 # TODO: Suppress the error message.
     66 .if !${INDIRECT}
     67 .  error
     68 .endif
     69