29 lines
888 B
Makefile
29 lines
888 B
Makefile
# $NetBSD: counter-append.mk,v 1.5 2021/04/04 10:13:09 rillig Exp $
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#
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# Demonstrates how to let make count the number of times a variable
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# is actually accessed, using the ::+= variable modifier.
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#
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# This works since 2020-09-23. Before that, the counter ended up at having
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# 6 words, even though the NEXT variable was only accessed 3 times.
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# The cause for this surprising behavior was that the ::= variable modifiers
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# returned an error marker instead of a simple empty string.
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RELEVANT= yes (load-time part) # just to filter the output
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COUNTER= # zero
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NEXT= ${COUNTER::+=a}${COUNTER:[#]}
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# This variable is first set to empty and then expanded.
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# See parse.c, function Parse_Var, keyword "!Var_Exists".
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A:= ${NEXT}
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B:= ${NEXT}
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C:= ${NEXT}
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RELEVANT= no
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all:
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@: ${RELEVANT::=yes (run-time part)}
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@echo A=${A:Q} B=${B:Q} C=${C:Q} COUNTER=${COUNTER:[#]:Q}
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@: ${RELEVANT::=no}
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