Index: doc/texinfo.tex
===================================================================
--- doc/texinfo.tex	(revision 6493)
+++ doc/texinfo.tex	(working copy)
@@ -7458,9 +7458,22 @@
   \usembodybackslash
 }
 
+% \macroargbackslash
+% - expand \\ as \, otherwise keep \ as it is.
+{ address@hidden @address@hidden@active
address@hidden@macroargbackslash#1{%
+% we need noexpand because \ is active
address@hidden @noexpand address@hidden address@hidden
address@hidden @normalbackslash #1%
address@hidden
+
address@hidden@address@hidden@macroargbackslash}
+}
+
 \def\macroargctxt{% used when scanning invocations
   \scanctxt
-  \catcode`\\=0
+  \catcode`\\=\active
+  %\catcode`\\=0
 }
 % why catcode 0 for \ in the above?  To recognize \\ \{ \} as "escapes"
 % for the single characters \ { }.  Thus, we end up with the "commands"
@@ -7838,11 +7851,10 @@
         \noexpand\scanmacro{\temp}}%
     \or % 1
       \expandafter\xdef\csname\the\macname\endcsname{%
-         \bgroup
          \noexpand\braceorline
          \expandafter\noexpand\csname\the\macname xxx\endcsname}%
       \expandafter\xdef\csname\the\macname xxx\endcsname##1{%
-         \egroup\noexpand\scanmacro{\temp}}%
+         \egroup\noexpand\scanmacro{\temp}\egroup}%
     \else
       \ifnum\paramno<10\relax % at most 9
         \expandafter\xdef\csname\the\macname\endcsname{%
@@ -7871,13 +7883,13 @@
         \noexpand\scanmacro{\temp}\egroup}%
     \or % 1
       \expandafter\xdef\csname\the\macname\endcsname{%
-         \bgroup
          \noexpand\braceorline
          \expandafter\noexpand\csname\the\macname xxx\endcsname}%
       \expandafter\xdef\csname\the\macname xxx\endcsname##1{%
         \egroup
         \noexpand\norecurse{\the\macname}%
-        \noexpand\scanmacro{\temp}\egroup}%
+        \noexpand\scanmacro{\temp}\egroup%
+        \egroup}%
     \else % at most 9
       \ifnum\paramno<10\relax
         \expandafter\xdef\csname\the\macname\endcsname{%
@@ -7907,16 +7919,33 @@
 
 \def\norecurse#1{\bgroup\cslet{#1}{macsave.#1}}
 
+\let\macroargdummy=\relax
+
+% Call #1 with a list of tokens #2, appending an unexpandable token to #2.
+% This allows a trailing active backslash in the argument not to eat the
+% next token.
+\def\callwithterminator#1#2{%
+#1{#2\macroargdummy}%
+}
+
 % \braceorline MAC is used for a one-argument macro MAC.  It checks
 % whether the next non-whitespace character is a {.  It sets the context
-% for reading the argument (slightly different in the two cases).  Then,
-% to read the argument, in the whole-line case, it then calls the
-% regular \parsearg MAC; in the lbrace case, it just calls MAC itself.
+% for reading the argument (slightly different in the two cases).  It
+% opens two groups for this: the inner for reading the argument, the
+% outer for an optional active character definition to remain in place
+% for the macro body.
 % 
+% To read the argument, in the whole-line case, it then calls the
+% regular \parsearg MAC; in the lbrace case, it calls
+% \callwithterminator MAC.
+% 
 \def\braceorline#1{\let\macnamexxx=#1\futurelet\nchar\braceorlinexxx}
 \def\braceorlinexxx{%
-  \ifx\nchar\bgroup\macroargctxt
-  \else\macrolineargctxt\expandafter\parsearg
+  \ifx\nchar\bgroup
+    \bgroup\usemacroargbackslash\bgroup\macroargctxt
+                                   %\expandafter\callwithterminator
+  \else
+    \bgroup\bgroup\macrolineargctxt\expandafter\parsearg
   \fi \macnamexxx}