doc: document GNU make's \#

* doc/autoconf.texi (Comments in Make Macros): Also mention \#
in the right hand side of a macro, as an unportable usage.

diff --git a/ChangeLog b/ChangeLog
index 68dffefecb02cc430b094917530ff647625f64c1..f9f4b907d636c7c880bcc51680ef7818a657c6fa 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2011-12-05  Paul Eggert  <eggert@cs.ucla.edu>
+
+       doc: document GNU make's \#
+       * doc/autoconf.texi (Comments in Make Macros): Also mention \#
+       in the right hand side of a macro, as an unportable usage.
+
 2011-11-11  Eric Blake  <eblake@redhat.com>
 
        doc: tweak previous commit

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 0569a276e746e757050c4818d8d266c43ed8c255..d7d2231cd862c1a673bd07f5c07a7402c1f8ed8a 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -20214,9 +20214,12 @@ CPPFLAGS = "-DCOMMENT_CHAR='#'"
 
 @noindent
 as @samp{CPPFLAGS} may be expanded to @samp{"-DCOMMENT_CHAR='}.
-Luckily, most @command{make} implementations disregard this and treat
-single and double quotes specially here; @pxref{Comments in Make Rules},
-for a more portable alternative.
+
+Most @command{make} implementations disregard this and treat single and
+double quotes specially here.  Also, GNU @command{make} lets you put
+@samp{#} into a macro value by escaping it with a backslash, i.e.,
+@samp{\#}.  However, neither of these usages are portable.
+@xref{Comments in Make Rules}, for a portable alternative.
 
 Even without quoting involved, comments can have surprising effects,
 because the whitespace before them is part of the variable value: