Avoid builtin concatenation in macro arguments.

* doc/m4.texinfo (Defn): Add tests.
* src/macro.c (warn_builtin_concat): New function.
(expand_argument): Use it to warn on more corner cases.
* NEWS: Mention new warning.

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

1 files changed, 5 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index b92630b8..d988adf3 100644
--- a/NEWS
+++ b/NEWS
@@ -7,11 +7,13 @@ Version 1.4.11 - ?? ??? 2007, by ????  (git version 1.4.10a-*)
 * Fix core dump in 'm4 -F file -t undefined', present since -F was
   introduced in 1.3.
 * Fix regression introduced in 1.4.9b in the `divert' builtin when more
-  than 512 kibibytes are saved in diversions on platforms like NetBSD
-  where fopen(name,"a+") seeks to the end of the file.
+  than 512 kibibytes are saved in diversions on platforms like NetBSD where
+  fopen(name,"a+") seeks to the end of the file.
 * Enhance the `defn' builtin to support concatenation of multiple text
   arguments, as required by POSIX.  However, at this time, it is not
-  possible to concatenate a builtin macro with anything else.
+  possible to concatenate a builtin macro with anything else; a warning is
+  now issued if this is attempted, although a future version of M4 may lift
+  this restriction to match other implementations.
 * Several improvements in `index', `regexp', and `patsubst' builtins to
   speed up typical Autoconf usage.
 * Memory usage is greatly reduced in recursive macros.