61 lines
1.6 KiB
Makefile
61 lines
1.6 KiB
Makefile
# $NetBSD: cond-op.mk,v 1.4 2020/08/28 14:07:51 rillig Exp $
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#
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# Tests for operators like &&, ||, ! in .if conditions.
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#
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# See also:
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# cond-op-and.mk
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# cond-op-not.mk
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# cond-op-or.mk
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# cond-op-parentheses.mk
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# In make, && binds more tightly than ||, like in C.
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# If make had the same precedence for both && and ||, the result would be
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# different.
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# If || were to bind more tightly than &&, the result would be different
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# as well.
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.if !(1 || 1 && 0)
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.error
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.endif
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# If make were to interpret the && and || operators like the shell, the
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# implicit binding would be this:
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.if (1 || 1) && 0
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.error
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.endif
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# The precedence of the ! operator is different from C though. It has a
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# lower precedence than the comparison operators.
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.if !"word" == "word"
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.error
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.endif
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# This is how the above condition is actually interpreted.
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.if !("word" == "word")
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.error
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.endif
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# TODO: Demonstrate that the precedence of the ! and == operators actually
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# makes a difference. There is a simple example for sure, I just cannot
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# wrap my head around it.
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# This condition is malformed because the '!' on the right-hand side must not
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# appear unquoted. If any, it must be enclosed in quotes.
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# In any case, it is not interpreted as a negation of an unquoted string.
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# See CondGetString.
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.if "!word" == !word
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.error
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.endif
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# Surprisingly, the ampersand and pipe are allowed in bare strings.
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# That's another opportunity for writing confusing code.
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# See CondGetString, which only has '!' in the list of stop characters.
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.if "a&&b||c" != a&&b||c
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.error
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.endif
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# Just in case that parsing should ever stop on the first error.
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.info Parsing continues until here.
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all:
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@:;
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