Tweak m4_do semantics.

* lib/m4sugar/m4sugar.m4 (m4_do): Don't concat final argument with
subsequent text.
* lib/m4sugar/foreach.m4 (m4_do): Don't concat intermediate
arguments, and avoid infinite loop.
* doc/autoconf.texi (Evaluation Macros) <m4_do>: Document the
behavior.
* tests/m4sugar.at (m4@&t@_do): New test.

Signed-off-by: Eric Blake <ebb9@byu.net>

ChangeLog

@@ -1,5 +1,14 @@
 2008-07-29  Eric Blake  <ebb9@byu.net>
 
+	Tweak m4_do semantics.
+	* lib/m4sugar/m4sugar.m4 (m4_do): Don't concat final argument with
+	subsequent text.
+	* lib/m4sugar/foreach.m4 (m4_do): Don't concat intermediate
+	arguments, and avoid infinite loop.
+	* doc/autoconf.texi (Evaluation Macros) <m4_do>: Document the
+	behavior.
+	* tests/m4sugar.at (m4@&t@_do): New test.
+
 	Optimize m4_for.
 	* lib/m4sugar/m4sugar.m4 (m4_for): Use fewer macros.
 	(_m4_for): Take additional parameter, for fewer m4_indir calls.

doc/autoconf.texi

@@ -10882,7 +10882,24 @@ passed.
 @msindex{do}
 This macro loops over its arguments and expands each @var{arg} in
 sequence.  Its main use is for readability; it allows the use of
-indentation and fewer @code{dnl} to result in the same expansion.
+indentation and fewer @code{dnl} to result in the same expansion.  This
+macro guarantees that no expansion will be concatenated with subsequent
+text; to achieve full concatenation, use @code{m4_unquote(m4_join([],
+@var{arg@dots{}}))}.
+
+@example
+m4_define([ab],[1])m4_define([bc],[2])m4_define([abc],[3])dnl
+m4_do([a],[b])c
+@result{}abc
+m4_unquote(m4_join([],[a],[b]))c
+@result{}3
+m4_define([a],[A])m4_define([b],[B])m4_define([c],[C])dnl
+m4_define([AB],[4])m4_define([BC],[5])m4_define([ABC],[6])dnl
+m4_do([a],[b])c
+@result{}ABC
+m4_unquote(m4_join([],[a],[b]))c
+@result{}3
+@end example
 @end defmac
 
 @defmac m4_dquote (@var{arg}, @dots{})

lib/m4sugar/foreach.m4

@@ -141,10 +141,11 @@ m4_define([_m4_shiftn],
 # unnecessary dnl's and have the macros indented properly.
 #
 # Here, we use the temporary macro _m4_do, defined as
-#   $1$2...$n[]_m4_popdef([_m4_do])
+#   $1[]$2[]...[]$n[]_m4_popdef([_m4_do])
 m4_define([m4_do],
-[m4_define([_$0], m4_pushdef([_$0])_m4_for([_$0], [1], [$#], [1],
-    [$_$0])[[]_m4_popdef([_$0])])_$0($@)])
+[m4_if([$#], [0], [],
+       [m4_define([_$0], m4_pushdef([_$0])_m4_for([_$0], [1], [$#], [1],
+		  [$_$0[[]]])[_m4_popdef([_$0])])_$0($@)])])
 
 # m4_dquote_elt(ARGS)
 # -------------------
@@ -200,7 +201,7 @@ m4_define([m4_join],
 #
 # A bit easier than m4_join.  m4_foreach to the rescue.
 m4_define([m4_joinall],
-[[$2]m4_if([$#], [1], [], [$#], [2], [],
+[[$2]m4_if(m4_eval([$# <= 2]), [1], [],
 	   [m4_foreach([_m4_arg], [m4_shift2($@)],
 		       [[$1]_m4_defn([_m4_arg])])])])
 

lib/m4sugar/m4sugar.m4

@@ -692,11 +692,12 @@ m4_define([m4_count], [$#])
 # ------------------
 # This macro invokes all its arguments (in sequence, of course).  It is
 # useful for making your macros more structured and readable by dropping
-# unnecessary dnl's and have the macros indented properly.
+# unnecessary dnl's and have the macros indented properly.  No concatenation
+# occurs after a STRING; use m4_unquote(m4_join(,STRING)) for that.
 m4_define([m4_do],
 [m4_if([$#], 0, [],
-       [$#], 1, [$1],
-       [$1[]m4_do(m4_shift($@))])])
+       [$#], 1, [$1[]],
+       [$1[]$0(m4_shift($@))])])
 
 
 # m4_dquote(ARGS)
@@ -816,6 +817,8 @@ m4_define([m4_reverse],
 # expansion.  For one argument, m4_unquote([arg]) is more efficient than
 # m4_do([arg]), but for multiple arguments, the difference is that
 # m4_unquote separates arguments with commas while m4_do concatenates.
+# Follow this macro with [] if concatenation with subsequent text is
+# undesired.
 m4_define([m4_unquote], [$*])
 
 

tests/m4sugar.at

@@ -237,6 +237,34 @@ m4_split([a )}@&t@>=- b -=<@&t@{( c])
 AT_CLEANUP
 
 
+## ------- ##
+## m4_do.  ##
+## ------- ##
+
+AT_SETUP([m4@&t@_do])
+
+AT_CHECK_M4SUGAR_TEXT(
+[[m4_define([ab], [1])m4_define([bc], [2])m4_define([abc], [3])dnl
+m4_define([AB], [4])m4_define([BC], [5])m4_define([ABC], [6])dnl
+m4_do
+m4_do([a])
+m4_do([a], [b])c
+m4_unquote(m4_join([], [a], [b]))c
+m4_define([a], [A])m4_define([b], [B])m4_define([c], [C])dnl
+m4_do([a], [b])c
+m4_unquote(m4_join([], [a], [b]))c
+]],
+[[
+a
+abc
+3
+ABC
+3
+]])
+
+AT_CLEANUP
+
+
 ## ----------- ##
 ## m4_append.  ##
 ## ----------- ##