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cond-undef-lint.mk revision 1.5 
      1 # $NetBSD: cond-undef-lint.mk,v 1.5 2024/08/06 18:00:17 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 !${DEF}
     19 .  error
     20 .endif
     21 
     22 # Since the condition fails to evaluate, neither of the branches is taken.
     23 # expect+2: Malformed conditional '${UNDEF}'
     24 # expect+1: Variable "UNDEF" is undefined
     25 .if ${UNDEF}
     26 .  error
     27 .else
     28 .  error
     29 .endif
     30 
     31 # The variable name depends on the undefined variable, which is probably a
     32 # mistake.  The variable UNDEF, as used here, can be easily turned into
     33 # an expression that is always defined, using the :U modifier.
     34 #
     35 # The outer expression does not generate an error message since there was
     36 # already an error evaluating this variable's name.
     37 #
     38 # TODO: Suppress the error message "Variable VAR. is undefined".  That part
     39 # of the expression must not be evaluated at all.
     40 # expect+3: Variable "UNDEF" is undefined
     41 # expect+2: Variable "VAR." is undefined
     42 # expect+1: Malformed conditional '${VAR.${UNDEF}}'
     43 .if ${VAR.${UNDEF}}
     44 .  error
     45 .else
     46 .  error
     47 .endif
     48 
     49 # The variable VAR.defined is not defined and thus generates an error message.
     50 #
     51 # TODO: This pattern looks a lot like CFLAGS.${OPSYS}, which is at least
     52 # debatable.  Or would any practical use of CFLAGS.${OPSYS} be via an indirect
     53 # expression, as in the next example?
     54 # expect+2: Variable "VAR.defined" is undefined
     55 # expect+1: Malformed conditional '${VAR.${DEF}}'
     56 .if ${VAR.${DEF}}
     57 .  error
     58 .else
     59 .  error
     60 .endif
     61 
     62 
     63 # Variables that are referenced indirectly may be undefined in a condition.
     64 #
     65 # A practical example for this is CFLAGS, which consists of CWARNS, COPTS
     66 # and a few others.  Just because these nested variables are not defined,
     67 # this does not make the condition invalid.
     68 #
     69 # The crucial point is that at the point where the variable appears in the
     70 # condition, there is no way to influence the definedness of the nested
     71 # variables.  In particular, there is no modifier that would turn undefined
     72 # nested variables into empty strings, as an equivalent to the :U modifier.
     73 INDIRECT=	${NESTED_UNDEF} ${NESTED_DEF}
     74 NESTED_DEF=	nested-defined
     75 
     76 # Since NESTED_UNDEF is not controllable at this point, it must not generate
     77 # an error message, and it doesn't do so, since 2020-09-14.
     78 .if !${INDIRECT}
     79 .  error
     80 .endif
     81