70 lines
1.8 KiB
Makefile
70 lines
1.8 KiB
Makefile
# $NetBSD: cond-token-var.mk,v 1.6 2021/04/25 21:05:38 rillig Exp $
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#
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# Tests for variable expressions in .if conditions.
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#
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# Note the fine distinction between a variable and a variable expression.
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# A variable has a name and a value. To access the value, one writes a
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# variable expression of the form ${VAR}. This is a simple variable
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# expression. Variable expressions can get more complicated by adding
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# variable modifiers such as in ${VAR:Mpattern}.
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#
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# XXX: Strictly speaking, variable modifiers should be called expression
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# modifiers instead since they only modify the expression, not the variable.
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# Well, except for the assignment modifiers, these do indeed change the value
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# of the variable.
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DEF= defined
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# A defined variable may appear on either side of the comparison.
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.if ${DEF} == ${DEF}
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. info ok
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.else
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. error
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.endif
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# A variable that appears on the left-hand side must be defined.
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# The following line thus generates a parse error.
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.if ${UNDEF} == ${DEF}
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. error
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.endif
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# A variable that appears on the right-hand side must be defined.
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# The following line thus generates a parse error.
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.if ${DEF} == ${UNDEF}
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. error
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.endif
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# A defined variable may appear as an expression of its own.
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.if ${DEF}
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.endif
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# An undefined variable on its own generates a parse error.
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.if ${UNDEF}
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.endif
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# The :U modifier turns an undefined expression into a defined expression.
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# Since the expression is defined now, it doesn't generate any parse error.
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.if ${UNDEF:U}
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.endif
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# If the value of the variable expression is a number, it is compared against
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# zero.
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.if ${:U0}
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. error
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.endif
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.if !${:U1}
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. error
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.endif
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# If the value of the variable expression is not a number, any non-empty
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# value evaluates to true, even if there is only whitespace.
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.if ${:U}
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. error
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.endif
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.if !${:U }
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. error
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.endif
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.if !${:Uanything}
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. error
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.endif
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