autoconf: Comments in Make Rules

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1 12.11 Comments in Make Rules
1 ============================
1 
1 Never put comments in a rule.
1 
1    Some `make' treat anything starting with a tab as a command for the
1 current rule, even if the tab is immediately followed by a `#'.  The
1 `make' from Tru64 Unix V5.1 is one of them.  The following makefile
1 runs `# foo' through the shell.
1 
1      all:
1              # foo
1 
1    As a workaround, you can use the `:' no-op command with a string
1 argument that gets ignored:
1 
1      all:
1              : "foo"
1 
1    Conversely, if you want to use the `#' character in some command,
11 you can only do so by expanding it inside a rule (⇒Comments in
 Make Macros).  So for example, if `COMMENT_CHAR' is substituted by
1 `config.status' as `#', then the following substitutes `@COMMENT_CHAR@'
1 in a generated header:
1 
1      foo.h: foo.h.in
1              sed -e 's|@''COMMENT_CHAR''@|@COMMENT_CHAR@|g' \
1                  $(srcdir)/foo.h.in > $@
1 
1    The funny shell quoting avoids a substitution at `config.status' run
1 time of the left-hand side of the `sed' `s' command.
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