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cond-cmp-unary.mk revision 1.3 
      1 # $NetBSD: cond-cmp-unary.mk,v 1.3 2022/09/08 05:43:20 rillig Exp $
      2 #
      3 # Tests for unary comparisons in .if conditions, that is, comparisons with
      4 # a single operand.  If the operand is a number, it is compared to zero,
      5 # if it is a string, it is tested for emptiness.
      6 
      7 # The number 0 in all its various representations evaluates to false.
      8 .if 0 || 0.0 || 0e0 || 0.0e0 || 0.0e10
      9 .  error
     10 .endif
     11 
     12 # Any other number evaluates to true.
     13 .if !12345
     14 .  error
     15 .endif
     16 
     17 # The empty string evaluates to false.
     18 .if ""
     19 .  error
     20 .endif
     21 
     22 # Any other string evaluates to true.
     23 .if !"0"
     24 .  error
     25 .endif
     26 
     27 # The empty string may come from a variable expression.
     28 #
     29 # XXX: As of 2020-11-11, this empty string is interpreted "as a number" in
     30 # EvalNotEmpty, which is plain wrong.  The bug is in TryParseNumber.
     31 .if ${:U}
     32 .  error
     33 .endif
     34 
     35 # A variable expression that is not surrounded by quotes is interpreted
     36 # as a number if possible, otherwise as a string.
     37 .if ${:U0}
     38 .  error
     39 .endif
     40 
     41 # A non-zero number from a variable expression evaluates to true.
     42 .if !${:U12345}
     43 .  error
     44 .endif
     45 
     46 # A string of whitespace should evaluate to false.
     47 #
     48 # XXX: As of 2020-11-11, the implementation in EvalNotEmpty does not skip
     49 # whitespace before testing for the end.  This was probably an oversight in
     50 # a commit from 1992-04-15 saying "A variable is empty when it just contains
     51 # spaces".
     52 .if ${:U   }
     53 .  info This is only reached because of a bug in EvalNotEmpty.
     54 .else
     55 .  error
     56 .endif
     57 
     58 # The condition '${VAR:M*}' is almost equivalent to '${VAR:M*} != ""'.  The
     59 # only case where they differ is for a single word whose numeric value is zero.
     60 .if ${:U0:M*}
     61 .  error
     62 .endif
     63 .if ${:U0:M*} == ""
     64 .  error
     65 .endif
     66 # Multiple words cannot be parsed as a single number, thus evaluating to true.
     67 .if !${:U0 0:M*}
     68 .  error
     69 .endif
     70 .if ${:U0 0:M*} == ""
     71 .  error
     72 .endif
     73 
     74 all: # nothing
     75