1# $NetBSD: directive-for-if.mk,v 1.1 2021/08/30 17:08:13 rillig Exp $ 2# 3# Test for a .for directive that contains an .if directive. 4# 5# Before for.c 1.39 from 2008-12-21, when expanding the variables of a .for 6# loop, their values were placed verbatim in the expanded body. Since then, 7# each variable value expands to an expression of the form ${:Uvalue}. 8# 9# Before that change, the following adventurous code was possible: 10# 11# .for directive in if ifdef ifndef 12# . ${directive} "1" != "0" 13# . endif 14# .endfor 15# 16# A more practical usage of the .for loop that often led to surprises was the 17# following: 18# 19# .for var in VAR1 VAR2 VAR3 20# . if ${var} != "VAR2" 21# . endif 22# .endfor 23# 24# The .for loop body expanded to this string: 25# 26# . if VAR1 != "VAR2" 27# . endif 28# 29# Since bare words were not allowed at the left-hand side of a condition, 30# make complained about a "Malformed conditional", which was surprising since 31# the code before expanding the .for loop body looked quite well. 32# 33# In cond.c 1.48 from 2008-11-29, just a month before the expansion of .for 34# loops changed from plain textual value to using expressions of the form 35# ${:Uvalue}, this surprising behavior was documented in the code, and a 36# workaround was implemented that allowed bare words when they are followed 37# by either '!' or '=', as part of the operators '!=' or '=='. 38# 39# Since cond.c 1.68 from 2015-05-05, bare words are allowed on the left-hand 40# side of a condition, but that applies only to expression of the form 41# ${${cond} :? then : else}, it does not apply to conditions in ordinary .if 42# directives. 43 44# The following snippet worked in 2005, when the variables from the .for loop 45# expanded to their bare textual value. 46.for directive in if ifdef ifndef 47. ${directive} "1" != "0" 48. endif 49.endfor 50# In 2021, the above code does not generate an error message, even though the 51# code looks clearly malformed. This is due to the '!', which is interpreted 52# as a dependency operator, similar to ':' and '::'. The parser turns this 53# line into a dependency with the 3 targets '.', 'if', '"1"' and the 2 sources 54# '=' and '"0"'. Since that line is not interpreted as an '.if' directive, 55# the error message 'if-less endif' makes sense. 56 57# In 2005, make complained: 58# 59# .if line: Malformed conditional (VAR1 != "VAR2") 60# .endif line: if-less endif 61# .endif line: Need an operator 62# 63# 2008.11.30.22.37.55 does not complain about the left-hand side ${var}. 64.for var in VAR1 VAR2 VAR3 65. if ${var} != "VAR2" 66_!= echo "${var}" 1>&2; echo # In 2005, '.info' was not invented yet. 67. endif 68.endfor 69 70# Before for.c 1.39 from 2008-12-21, a common workaround was to surround the 71# variable expression from the .for loop with '"'. Such a string literal 72# has been allowed since cond.c 1.23 from 2004-04-13. Between that commit and 73# the one from 2008, the parser would still get confused if the value from the 74# .for loop contained '"', which was effectively a code injection. 75# 76# Surrounding ${var} with quotes disabled the check for typos though. For 77# ordinary variables, referring to an undefined variable on the left-hand side 78# of the comparison resulted in a "Malformed conditional". Since the .for 79# loop was usually close to the .if clause, this was not a problem in 80# practice. 81.for var in VAR1 VAR2 VAR3 82. if "${var}" != "VAR2" 83. endif 84.endfor 85 86all: 87