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comment.mk revision 1.7 
      1 # $NetBSD: comment.mk,v 1.7 2024/04/23 22:51:28 rillig Exp $
      2 #
      3 # Demonstrate how comments are written in makefiles.
      4 
      5 # This is a comment.
      6 
      7 #\
      8 This is a multiline comment.
      9 
     10 # Another multiline comment \
     11 that \
     12 goes \
     13 on and on.
     14 
     15  # Comments can be indented with spaces, but that is rather unusual.
     16 
     17 	# Comments can be indented with a tab.
     18 	# Since parse.c 1.127 from 2007-01-01, these are not shell commands,
     19 	# they are just makefile comments.  Before that commit, these comments
     20 	# triggered the error message "Unassociated shell command".
     21 
     22 .if 1			# There can be comments after conditions.
     23 .endif			# And after the closing directive.
     24 
     25 VAR=			# This comment makes the variable value empty.
     26 			# ParseRawLine removes any whitespace before the
     27 			# comment.
     28 .if ${VAR} != ""
     29 .  error
     30 .endif
     31 
     32 # The comment does not need to start at the beginning of a word (as in the
     33 # shell), it can start anywhere.
     34 VAR=# defined but empty
     35 
     36 # The space before the comment is always trimmed.
     37 VAR=	value
     38 .if ${VAR} != "value"
     39 .  error
     40 .endif
     41 
     42 # This comment ends with 2 backslashes.  An even number of backslashes does
     43 # not count as a line continuation, therefore the variable assignment that
     44 # follows is actively interpreted. \\
     45 VAR=	not part of the comment
     46 .if ${VAR} != "not part of the comment"
     47 .  error
     48 .endif
     49 
     50 # To escape a comment sign, precede it with a backslash.
     51 VAR=	\#		# Both in the assignment.
     52 .if ${VAR} != "\#"	# And in the comparison.
     53 .  error
     54 .endif
     55 
     56 # Since 2012-03-24 the modifier :[#] does not need to be escaped.
     57 # To keep the parsing code simple, the "#" in "[#" does not start a comment,
     58 # regardless of the syntactical context it appears in.
     59 WORDS=	${VAR:[#]} [#
     60 .if ${WORDS} != "1 [#"
     61 .  error
     62 .endif
     63 
     64 # An odd number of backslashes makes a line continuation, \\\
     65 no matter if it is 3 or 5 \\\\\
     66 or 9 backslashes. \\\\\\\\\
     67 This is the last line of the comment.
     68 VAR=	no comment anymore
     69 .if ${VAR} != "no comment anymore"
     70 .  error
     71 .endif
     72 
     73 all:
     74 # In the commands associated with a target, the '#' does not start a makefile
     75 # comment.  The '#' is just passed to the shell, like any ordinary character.
     76 	echo This is a shell comment: # comment
     77 # If the '#' were to start a makefile comment, the following shell command
     78 # would have unbalanced quotes.
     79 	echo This is not a shell comment: '# comment'
     80 	@echo A shell comment can#not start in the middle of a word.
     81