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modmisc.mk revision 1.36
      1  1.36  rillig # $Id: modmisc.mk,v 1.36 2020/08/08 13:09:55 rillig Exp $
      2   1.1     apb #
      3   1.1     apb # miscellaneous modifier tests
      4   1.1     apb 
      5   1.1     apb # do not put any dirs in this list which exist on some
      6   1.1     apb # but not all target systems - an exists() check is below.
      7   1.1     apb path=:/bin:/tmp::/:.:/no/such/dir:.
      8   1.1     apb # strip cwd from path.
      9   1.1     apb MOD_NODOT=S/:/ /g:N.:ts:
     10   1.1     apb # and decorate, note that $'s need to be doubled. Also note that 
     11   1.1     apb # the modifier_variable can be used with other modifiers.
     12   1.1     apb MOD_NODOTX=S/:/ /g:N.:@d@'$$d'@
     13   1.1     apb # another mod - pretend it is more interesting
     14   1.1     apb MOD_HOMES=S,/home/,/homes/,
     15   1.1     apb MOD_OPT=@d@$${exists($$d):?$$d:$${d:S,/usr,/opt,}}@
     16   1.1     apb MOD_SEP=S,:, ,g
     17   1.1     apb 
     18   1.7  rillig all:	modvar modvarloop modsysv mod-HTE emptyvar undefvar
     19  1.23  rillig all:	mod-subst
     20  1.30  rillig all:	mod-subst-chain
     21  1.23  rillig all:	mod-regex
     22  1.23  rillig all:	mod-loop-varname mod-loop-resolve mod-loop-varname-dollar
     23  1.12  rillig all:	mod-subst-dollar mod-loop-dollar
     24  1.23  rillig all:	mod-regex-limits
     25  1.23  rillig all:	mod-regex-errors
     26  1.16  rillig all:	mod-assign
     27  1.18  rillig all:	mod-assign-nested
     28  1.17  rillig all:	mod-tu-space
     29  1.23  rillig all:	mod-quote
     30  1.22  rillig all:	mod-break-many-words
     31  1.27  rillig all:	mod-remember
     32  1.28  rillig all:	mod-gmtime
     33  1.36  rillig all:	mod-gmtime-indirect
     34  1.28  rillig all:	mod-localtime
     35  1.28  rillig all:	mod-hash
     36  1.28  rillig all:	mod-range
     37   1.1     apb 
     38  1.23  rillig # See also sysv.mk.
     39   1.1     apb modsysv:
     40   1.1     apb 	@echo "The answer is ${libfoo.a:L:libfoo.a=42}"
     41   1.1     apb 
     42  1.23  rillig # Demonstrates modifiers that are given indirectly from a variable.
     43   1.1     apb modvar:
     44   1.1     apb 	@echo "path='${path}'"
     45   1.1     apb 	@echo "path='${path:${MOD_NODOT}}'"
     46   1.1     apb 	@echo "path='${path:S,home,homes,:${MOD_NODOT}}'"
     47   1.1     apb 	@echo "path=${path:${MOD_NODOTX}:ts:}"
     48   1.1     apb 	@echo "path=${path:${MOD_HOMES}:${MOD_NODOTX}:ts:}"
     49   1.1     apb 
     50   1.1     apb .for d in ${path:${MOD_SEP}:N.} /usr/xbin
     51   1.1     apb path_$d?= ${d:${MOD_OPT}:${MOD_HOMES}}/
     52   1.1     apb paths+= ${d:${MOD_OPT}:${MOD_HOMES}}
     53   1.1     apb .endfor
     54   1.1     apb 
     55   1.1     apb modvarloop:
     56   1.1     apb 	@echo "path_/usr/xbin=${path_/usr/xbin}"
     57   1.1     apb 	@echo "paths=${paths}"
     58   1.1     apb 	@echo "PATHS=${paths:tu}"
     59   1.2  rillig 
     60   1.6  rillig PATHNAMES=	a/b/c def a.b.c a.b/c a a.a .gitignore a a.a
     61   1.4  rillig mod-HTE:
     62   1.6  rillig 	@echo "dirname of '"${PATHNAMES:Q}"' is '"${PATHNAMES:H:Q}"'"
     63   1.6  rillig 	@echo "basename of '"${PATHNAMES:Q}"' is '"${PATHNAMES:T:Q}"'"
     64   1.6  rillig 	@echo "suffix of '"${PATHNAMES:Q}"' is '"${PATHNAMES:E:Q}"'"
     65   1.6  rillig 	@echo "root of '"${PATHNAMES:Q}"' is '"${PATHNAMES:R:Q}"'"
     66   1.7  rillig 
     67   1.7  rillig # When a modifier is applied to the "" variable, the result is discarded.
     68   1.7  rillig emptyvar:
     69   1.7  rillig 	@echo S:${:S,^$,empty,}
     70   1.7  rillig 	@echo C:${:C,^$,empty,}
     71   1.7  rillig 	@echo @:${:@var@${var}@}
     72   1.7  rillig 
     73   1.7  rillig # The :U modifier turns even the "" variable into something that has a value.
     74   1.7  rillig # The resulting variable is empty, but is still considered to contain a
     75   1.7  rillig # single empty word. This word can be accessed by the :S and :C modifiers,
     76   1.7  rillig # but not by the :@ modifier since it explicitly skips empty words.
     77   1.7  rillig undefvar:
     78   1.7  rillig 	@echo S:${:U:S,^$,empty,}
     79   1.7  rillig 	@echo C:${:U:C,^$,empty,}
     80   1.7  rillig 	@echo @:${:U:@var@empty@}
     81   1.8  rillig 
     82  1.24  rillig WORDS=		sequences of letters
     83  1.26  rillig .if ${WORDS:S,,,} != ${WORDS}
     84  1.26  rillig .warning The empty pattern matches something.
     85  1.26  rillig .endif
     86  1.25  rillig .if ${WORDS:S,e,*,1} != "s*quences of letters"
     87  1.26  rillig .warning The :S modifier flag '1' is not applied exactly once.
     88  1.24  rillig .endif
     89  1.24  rillig .if ${WORDS:S,e,*,} != "s*quences of l*tters"
     90  1.26  rillig .warning The :S modifier does not replace every first match per word.
     91  1.24  rillig .endif
     92  1.24  rillig .if ${WORDS:S,e,*,g} != "s*qu*nc*s of l*tt*rs"
     93  1.26  rillig .warning The :S modifier flag 'g' does not replace every occurrence.
     94  1.24  rillig .endif
     95  1.24  rillig .if ${WORDS:S,^sequ,occurr,} != "occurrences of letters"
     96  1.26  rillig .warning The :S modifier fails for a short match anchored at the start.
     97  1.24  rillig .endif
     98  1.24  rillig .if ${WORDS:S,^of,with,} != "sequences with letters"
     99  1.26  rillig .warning The :S modifier fails for an exact match anchored at the start.
    100  1.24  rillig .endif
    101  1.24  rillig .if ${WORDS:S,^office,does not match,} != ${WORDS}
    102  1.26  rillig .warning The :S modifier matches a too long pattern anchored at the start.
    103  1.26  rillig .endif
    104  1.26  rillig .if ${WORDS:S,f$,r,} != "sequences or letters"
    105  1.26  rillig .warning The :S modifier fails for a short match anchored at the end.
    106  1.26  rillig .endif
    107  1.26  rillig .if ${WORDS:S,s$,,} != "sequence of letter"
    108  1.26  rillig .warning The :S modifier fails to replace one occurrence per word.
    109  1.26  rillig .endif
    110  1.26  rillig .if ${WORDS:S,of$,,} != "sequences letters"
    111  1.26  rillig .warning The :S modifier fails for an exact match anchored at the end.
    112  1.26  rillig .endif
    113  1.26  rillig .if ${WORDS:S,eof$,,} != ${WORDS}
    114  1.26  rillig .warning The :S modifier matches a too long pattern anchored at the end.
    115  1.26  rillig .endif
    116  1.26  rillig .if ${WORDS:S,^of$,,} != "sequences letters"
    117  1.26  rillig .warning The :S modifier does not match a word anchored at both ends.
    118  1.26  rillig .endif
    119  1.26  rillig .if ${WORDS:S,^o$,,} != ${WORDS}
    120  1.26  rillig .warning The :S modifier matches a prefix anchored at both ends.
    121  1.26  rillig .endif
    122  1.26  rillig .if ${WORDS:S,^f$,,} != ${WORDS}
    123  1.26  rillig .warning The :S modifier matches a suffix anchored at both ends.
    124  1.26  rillig .endif
    125  1.26  rillig .if ${WORDS:S,^eof$,,} != ${WORDS}
    126  1.26  rillig .warning The :S modifier matches a too long prefix anchored at both ends.
    127  1.26  rillig .endif
    128  1.26  rillig .if ${WORDS:S,^office$,,} != ${WORDS}
    129  1.26  rillig .warning The :S modifier matches a too long suffix anchored at both ends.
    130  1.24  rillig .endif
    131  1.24  rillig 
    132  1.23  rillig mod-subst:
    133  1.20  rillig 	@echo $@:
    134   1.8  rillig 	@echo :${:Ua b b c:S,a b,,:Q}:
    135   1.8  rillig 	@echo :${:Ua b b c:S,a b,,1:Q}:
    136   1.8  rillig 	@echo :${:Ua b b c:S,a b,,W:Q}:
    137   1.8  rillig 	@echo :${:Ua b b c:S,b,,g:Q}:
    138   1.8  rillig 	@echo :${:U1 2 3 1 2 3:S,1 2,___,Wg:S,_,x,:Q}:
    139  1.20  rillig 	@echo ${:U12345:S,,sep,g:Q}
    140   1.8  rillig 
    141  1.30  rillig # The :S and :C modifiers can be chained without a separating ':'.
    142  1.30  rillig # This is not documented in the manual page.
    143  1.30  rillig # It works because ApplyModifier_Subst scans for the known modifiers g1W
    144  1.30  rillig # and then just returns to ApplyModifiers.  There, the colon is optionally
    145  1.30  rillig # skipped (see the *st.next == ':' at the end of the loop).
    146  1.30  rillig #
    147  1.30  rillig # Most other modifiers cannot be chained since their parsers skip until
    148  1.30  rillig # the next ':' or '}' or ')'.
    149  1.30  rillig mod-subst-chain:
    150  1.30  rillig 	@echo $@:
    151  1.30  rillig 	@echo ${:Ua b c:S,a,A,S,b,B,}.
    152  1.35  rillig 	# There is no 'i' modifier for the :S or :C modifiers.
    153  1.35  rillig 	# The error message is "make: Unknown modifier 'i'", which is
    154  1.35  rillig 	# kind of correct, although it is mixing the terms for variable
    155  1.35  rillig 	# modifiers with the matching modifiers.
    156  1.35  rillig 	@echo ${:Uvalue:S,a,x,i}.
    157  1.30  rillig 
    158  1.23  rillig mod-regex:
    159  1.20  rillig 	@echo $@:
    160   1.8  rillig 	@echo :${:Ua b b c:C,a b,,:Q}:
    161   1.8  rillig 	@echo :${:Ua b b c:C,a b,,1:Q}:
    162   1.8  rillig 	@echo :${:Ua b b c:C,a b,,W:Q}:
    163   1.8  rillig 	@echo :${:Uword1 word2:C,****,____,g:C,word,____,:Q}:
    164   1.8  rillig 	@echo :${:Ua b b c:C,b,,g:Q}:
    165   1.8  rillig 	@echo :${:U1 2 3 1 2 3:C,1 2,___,Wg:C,_,x,:Q}:
    166   1.9  rillig 
    167   1.9  rillig # In the :@ modifier, the name of the loop variable can even be generated
    168   1.9  rillig # dynamically.  There's no practical use-case for this, and hopefully nobody
    169   1.9  rillig # will ever depend on this, but technically it's possible.
    170  1.33  rillig # Therefore, in -dL mode, this is forbidden, see lint.mk.
    171  1.23  rillig mod-loop-varname:
    172   1.9  rillig 	@echo :${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@:Q}:
    173  1.34  rillig 	# ":::" is a very creative variable name, unlikely in practice
    174  1.34  rillig 	# The expression ${\:\:\:} would not work since backslashes can only
    175  1.34  rillig 	# be escaped in the modifiers, but not in the variable name.
    176  1.34  rillig 	@echo :${:U1 2 3:@:::@x${${:U\:\:\:}}y@}:
    177  1.34  rillig 	# "@@" is another creative variable name.
    178  1.34  rillig 	@echo :${:U1 2 3:@\@\@@x${@@}y@}:
    179  1.34  rillig 	# Even "@" works as a variable name since the variable is installed
    180  1.34  rillig 	# in the "current" scope, which in this case is the one from the
    181  1.34  rillig 	# target.
    182  1.34  rillig 	@echo :$@: :${:U1 2 3:@\@@x${@}y@}: :$@:
    183  1.34  rillig 	# In extreme cases, even the backslash can be used as variable name.
    184  1.34  rillig 	# It needs to be doubled though.
    185  1.34  rillig 	@echo :${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@}:
    186  1.10  rillig 
    187  1.10  rillig # The :@ modifier resolves the variables a little more often than expected.
    188  1.10  rillig # In particular, it resolves _all_ variables from the context, and not only
    189  1.10  rillig # the loop variable (in this case v).
    190  1.11  rillig #
    191  1.11  rillig # The d means direct reference, the i means indirect reference.
    192  1.10  rillig RESOLVE=	${RES1} $${RES1}
    193  1.11  rillig RES1=		1d${RES2} 1i$${RES2}
    194  1.11  rillig RES2=		2d${RES3} 2i$${RES3}
    195  1.11  rillig RES3=		3
    196  1.10  rillig 
    197  1.23  rillig mod-loop-resolve:
    198  1.10  rillig 	@echo $@:${RESOLVE:@v@w${v}w@:Q}:
    199  1.12  rillig 
    200  1.23  rillig # Until 2020-07-20, the variable name of the :@ modifier could end with one
    201  1.23  rillig # or two dollar signs, which were silently ignored.
    202  1.23  rillig # There's no point in allowing a dollar sign in that position.
    203  1.23  rillig mod-loop-varname-dollar:
    204  1.13  rillig 	@echo $@:${1 2 3:L:@v$@($v)@:Q}.
    205  1.13  rillig 	@echo $@:${1 2 3:L:@v$$@($v)@:Q}.
    206  1.13  rillig 	@echo $@:${1 2 3:L:@v$$$@($v)@:Q}.
    207  1.13  rillig 
    208  1.12  rillig # No matter how many dollar characters there are, they all get merged
    209  1.12  rillig # into a single dollar by the :S modifier.
    210  1.12  rillig mod-subst-dollar:
    211  1.12  rillig 	@echo $@:${:U1:S,^,$,:Q}:
    212  1.12  rillig 	@echo $@:${:U2:S,^,$$,:Q}:
    213  1.12  rillig 	@echo $@:${:U3:S,^,$$$,:Q}:
    214  1.12  rillig 	@echo $@:${:U4:S,^,$$$$,:Q}:
    215  1.12  rillig 	@echo $@:${:U5:S,^,$$$$$,:Q}:
    216  1.12  rillig 	@echo $@:${:U6:S,^,$$$$$$,:Q}:
    217  1.12  rillig 	@echo $@:${:U7:S,^,$$$$$$$,:Q}:
    218  1.12  rillig 	@echo $@:${:U8:S,^,$$$$$$$$,:Q}:
    219  1.12  rillig # This generates no dollar at all:
    220  1.12  rillig 	@echo $@:${:UU8:S,^,${:U$$$$$$$$},:Q}:
    221  1.12  rillig # Here is an alternative way to generate dollar characters.
    222  1.12  rillig # It's unexpectedly complicated though.
    223  1.12  rillig 	@echo $@:${:U:range=5:ts\x24:C,[0-9],,g:Q}:
    224  1.12  rillig 
    225  1.12  rillig # Demonstrate that it is possible to generate dollar characters using the
    226  1.12  rillig # :@ modifier.
    227  1.12  rillig #
    228  1.12  rillig # These are edge cases that could have resulted in a parse error as well
    229  1.12  rillig # since the $@ at the end could have been interpreted as a variable, which
    230  1.12  rillig # would mean a missing closing @ delimiter.
    231  1.12  rillig mod-loop-dollar:
    232  1.12  rillig 	@echo $@:${:U1:@word@${word}$@:Q}:
    233  1.12  rillig 	@echo $@:${:U2:@word@$${word}$$@:Q}:
    234  1.12  rillig 	@echo $@:${:U3:@word@$$${word}$$$@:Q}:
    235  1.12  rillig 	@echo $@:${:U4:@word@$$$${word}$$$$@:Q}:
    236  1.12  rillig 	@echo $@:${:U5:@word@$$$$${word}$$$$$@:Q}:
    237  1.12  rillig 	@echo $@:${:U6:@word@$$$$$${word}$$$$$$@:Q}:
    238  1.14  rillig 
    239  1.23  rillig mod-regex-limits:
    240  1.14  rillig 	@echo $@:00-ok:${:U1 23 456:C,..,\0\0,:Q}
    241  1.14  rillig 	@echo $@:11-missing:${:U1 23 456:C,..,\1\1,:Q}
    242  1.14  rillig 	@echo $@:11-ok:${:U1 23 456:C,(.).,\1\1,:Q}
    243  1.14  rillig 	@echo $@:22-missing:${:U1 23 456:C,..,\2\2,:Q}
    244  1.14  rillig 	@echo $@:22-missing:${:U1 23 456:C,(.).,\2\2,:Q}
    245  1.14  rillig 	@echo $@:22-ok:${:U1 23 456:C,(.)(.),\2\2,:Q}
    246  1.15  rillig 	# The :C modifier only handles single-digit capturing groups,
    247  1.15  rillig 	# which is more than enough for daily use.
    248  1.15  rillig 	@echo $@:capture:${:UabcdefghijABCDEFGHIJrest:C,(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.),\9\8\7\6\5\4\3\2\1\0\10\11\12,}
    249  1.16  rillig 
    250  1.23  rillig mod-regex-errors:
    251  1.21  rillig 	@echo $@: ${UNDEF:Uvalue:C,[,,}
    252  1.21  rillig 
    253  1.16  rillig # Just a bit of basic code coverage for the obscure ::= assignment modifiers.
    254  1.16  rillig mod-assign:
    255  1.16  rillig 	@echo $@: ${1 2 3:L:@i@${FIRST::?=$i}@} first=${FIRST}.
    256  1.16  rillig 	@echo $@: ${1 2 3:L:@i@${LAST::=$i}@} last=${LAST}.
    257  1.16  rillig 	@echo $@: ${1 2 3:L:@i@${APPENDED::+=$i}@} appended=${APPENDED}.
    258  1.16  rillig 	@echo $@: ${echo.1 echo.2 echo.3:L:@i@${RAN::!=${i:C,.*,&; & 1>\&2,:S,., ,g}}@} ran:${RAN}.
    259  1.16  rillig 	# The assignments happen in the global scope and thus are
    260  1.16  rillig 	# preserved even after the shell command has been run.
    261  1.16  rillig 	@echo $@: global: ${FIRST:Q}, ${LAST:Q}, ${APPENDED:Q}, ${RAN:Q}.
    262  1.17  rillig 
    263  1.18  rillig mod-assign-nested:
    264  1.18  rillig 	@echo $@: ${1:?${THEN1::=then1${IT1::=t1}}:${ELSE1::=else1${IE1::=e1}}}${THEN1}${ELSE1}${IT1}${IE1}
    265  1.18  rillig 	@echo $@: ${0:?${THEN2::=then2${IT2::=t2}}:${ELSE2::=else2${IE2::=e2}}}${THEN2}${ELSE2}${IT2}${IE2}
    266  1.18  rillig 	@echo $@: ${SINK3:Q}
    267  1.18  rillig 	@echo $@: ${SINK4:Q}
    268  1.18  rillig SINK3:=	${1:?${THEN3::=then3${IT3::=t3}}:${ELSE3::=else3${IE3::=e3}}}${THEN3}${ELSE3}${IT3}${IE3}
    269  1.18  rillig SINK4:=	${0:?${THEN4::=then4${IT4::=t4}}:${ELSE4::=else4${IE4::=e4}}}${THEN4}${ELSE4}${IT4}${IE4}
    270  1.18  rillig 
    271  1.17  rillig mod-tu-space:
    272  1.17  rillig 	# The :tu and :tl modifiers operate on the variable value
    273  1.17  rillig 	# as a single string, not as a list of words. Therefore,
    274  1.17  rillig 	# the adjacent spaces are preserved.
    275  1.17  rillig 	@echo $@: ${a   b:L:tu:Q}
    276  1.19  rillig 
    277  1.23  rillig mod-quote:
    278  1.19  rillig 	@echo $@: new${.newline:Q}${.newline:Q}line
    279  1.22  rillig 
    280  1.22  rillig # Cover the bmake_realloc in brk_string.
    281  1.22  rillig mod-break-many-words:
    282  1.22  rillig 	@echo $@: ${UNDEF:U:range=500:[#]}
    283  1.27  rillig 
    284  1.27  rillig # Demonstrate the :_ modifier.
    285  1.27  rillig # In the parameterized form, having the variable name on the right side
    286  1.27  rillig # of the = assignment operator is confusing. Luckily this modifier is
    287  1.27  rillig # only rarely needed.
    288  1.27  rillig mod-remember:
    289  1.27  rillig 	@echo $@: ${1 2 3:L:_:@var@${_}@}
    290  1.27  rillig 	@echo $@: ${1 2 3:L:@var@${var:_=SAVED:}@}, SAVED=${SAVED}
    291  1.28  rillig 
    292  1.28  rillig mod-gmtime:
    293  1.28  rillig 	@echo $@:
    294  1.28  rillig 	@echo ${%Y:L:gmtim=1593536400}		# modifier name too short
    295  1.28  rillig 	@echo ${%Y:L:gmtime=1593536400}		# 2020-07-01T00:00:00Z
    296  1.28  rillig 	@echo ${%Y:L:gmtimer=1593536400}	# modifier name too long
    297  1.29  rillig 	@echo ${%Y:L:gm=gm:M*}
    298  1.28  rillig 
    299  1.36  rillig mod-gmtime-indirect:
    300  1.36  rillig 	@echo $@:
    301  1.36  rillig 	# It's not possible to pass the seconds via a variable expression.
    302  1.36  rillig 	# Parsing of the :gmtime modifier stops at the '$' and returns to
    303  1.36  rillig 	# ApplyModifiers.  There, a colon would be skipped but not a dollar.
    304  1.36  rillig 	# Parsing continues by looking at the next modifier.  Now the ${:U}
    305  1.36  rillig 	# is expanded and interpreted as a variable modifier, which results
    306  1.36  rillig 	# in the error message "Unknown modifier '1'".
    307  1.36  rillig 	@echo ${%Y:L:gmtime=${:U1593536400}}
    308  1.36  rillig 
    309  1.28  rillig mod-localtime:
    310  1.28  rillig 	@echo $@:
    311  1.28  rillig 	@echo ${%Y:L:localtim=1593536400}	# modifier name too short
    312  1.28  rillig 	@echo ${%Y:L:localtime=1593536400}	# 2020-07-01T00:00:00Z
    313  1.28  rillig 	@echo ${%Y:L:localtimer=1593536400}	# modifier name too long
    314  1.28  rillig 
    315  1.28  rillig mod-hash:
    316  1.28  rillig 	@echo $@:
    317  1.28  rillig 	@echo ${12345:L:has}			# modifier name too short
    318  1.28  rillig 	@echo ${12345:L:hash}			# ok
    319  1.28  rillig 	@echo ${12345:L:hash=SHA-256}		# :hash does not accept '='
    320  1.28  rillig 	@echo ${12345:L:hasX}			# misspelled
    321  1.28  rillig 	@echo ${12345:L:hashed}			# modifier name too long
    322  1.28  rillig 
    323  1.28  rillig mod-range:
    324  1.28  rillig 	@echo $@:
    325  1.28  rillig 	@echo ${a b c:L:rang}			# modifier name too short
    326  1.28  rillig 	@echo ${a b c:L:range}			# ok
    327  1.28  rillig 	@echo ${a b c:L:rango}			# misspelled
    328  1.28  rillig 	@echo ${a b c:L:ranger}			# modifier name too long
    329  1.31  rillig 
    330  1.31  rillig # To apply a modifier indirectly via another variable, the whole
    331  1.31  rillig # modifier must be put into a single variable.
    332  1.31  rillig .if ${value:L:${:US}${:U,value,replacement,}} != "S,value,replacement,}"
    333  1.31  rillig .warning unexpected
    334  1.31  rillig .endif
    335  1.31  rillig 
    336  1.31  rillig # Adding another level of indirection (the 2 nested :U expressions) helps.
    337  1.31  rillig .if ${value:L:${:U${:US}${:U,value,replacement,}}} != "replacement"
    338  1.31  rillig .warning unexpected
    339  1.31  rillig .endif
    340  1.31  rillig 
    341  1.31  rillig # Multiple indirect modifiers can be applied one after another as long as
    342  1.31  rillig # they are separated with colons.
    343  1.31  rillig .if ${value:L:${:US,a,A,}:${:US,e,E,}} != "vAluE"
    344  1.31  rillig .warning unexpected
    345  1.31  rillig .endif
    346  1.32  rillig 
    347  1.32  rillig # An indirect variable that evaluates to the empty string is allowed though.
    348  1.32  rillig # This makes it possible to define conditional modifiers, like this:
    349  1.32  rillig #
    350  1.32  rillig # M.little-endian=	S,1234,4321,
    351  1.32  rillig # M.big-endian=		# none
    352  1.32  rillig .if ${value:L:${:Dempty}S,a,A,} != "vAlue"
    353  1.32  rillig .warning unexpected
    354  1.32  rillig .endif
    355