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cond-undef-lint.mk revision 1.7 
      1 # $NetBSD: cond-undef-lint.mk,v 1.7 2025/01/11 20:54:45 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 # See also:
     10 #	opt-debug-lint.mk
     11 
     12 .MAKEFLAGS: -dL
     13 
     14 # DEF is defined, UNDEF is not.
     15 DEF=		defined
     16 
     17 # An expression based on a defined variable is fine.
     18 .if !${DEF}
     19 .  error
     20 .endif
     21 
     22 # Since the condition fails to evaluate, neither of the branches is taken.
     23 # expect+1: Variable "UNDEF" is undefined
     24 .if ${UNDEF}
     25 .  error
     26 .else
     27 .  error
     28 .endif
     29 
     30 # The variable name depends on the undefined variable, which is probably a
     31 # mistake.  The variable UNDEF, as used here, can be easily turned into
     32 # an expression that is always defined, using the :U modifier.
     33 #
     34 # The outer expression does not generate an error message since there was
     35 # already an error evaluating this variable's name.
     36 #
     37 # TODO: Suppress the error message "Variable VAR. is undefined".  That part
     38 # of the expression must not be evaluated at all.
     39 # expect+2: Variable "UNDEF" is undefined
     40 # expect+1: Variable "VAR." is undefined
     41 .if ${VAR.${UNDEF}}
     42 .  error
     43 .else
     44 .  error
     45 .endif
     46 
     47 # The variable VAR.defined is not defined and thus generates an error message.
     48 #
     49 # TODO: This pattern looks a lot like CFLAGS.${OPSYS}, which is at least
     50 # debatable.  Or would any practical use of CFLAGS.${OPSYS} be via an indirect
     51 # expression, as in the next example?
     52 # expect+1: Variable "VAR.defined" is undefined
     53 .if ${VAR.${DEF}}
     54 .  error
     55 .else
     56 .  error
     57 .endif
     58 
     59 
     60 # Variables that are referenced indirectly may be undefined in a condition.
     61 #
     62 # A practical example for this is CFLAGS, which consists of CWARNS, COPTS
     63 # and a few others.  Just because these nested variables are not defined,
     64 # this does not make the condition invalid.
     65 #
     66 # The crucial point is that at the point where the variable appears in the
     67 # condition, there is no way to influence the definedness of the nested
     68 # variables.  In particular, there is no modifier that would turn undefined
     69 # nested variables into empty strings, as an equivalent to the :U modifier.
     70 INDIRECT=	${NESTED_UNDEF} ${NESTED_DEF}
     71 NESTED_DEF=	nested-defined
     72 
     73 # Since NESTED_UNDEF is not controllable at this point, it must not generate
     74 # an error message, and it doesn't do so, since 2020-09-14.
     75 .if !${INDIRECT}
     76 .  error
     77 .endif
     78