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(autoconf.info)Redefined M4 Macros

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Redefined M4 Macros
-------------------

   With a few exceptions, all the M4 native macros are moved in the
`m4_' pseudo-namespace, e.g., M4sugar renames `define' as `m4_define'
etc.

   Some M4 macros are redefined, and are slightly incompatible with
their native equivalent.

 - Macro: dnl
     This macro kept its original name: no `m4_dnl' is defined.

 - Macro: m4_defn (MACRO)
     Contrary to the M4 builtin, this macro fails if MACRO is not
     defined.  See `m4_undefine'.

 - Macro: m4_exit (EXIT-STATUS)
     This macro corresponds to `m4exit'.

 - Macro: m4_if (COMMENT)
 - Macro: m4_if (STRING-1, STRING-2, EQUAL, [NOT-EQUAL])
 - Macro: m4_if (STRING-1, STRING-2, EQUAL, ...)
     This macro corresponds to `ifelse'.

 - Macro: m4_undefine (MACRO)
     Contrary to the M4 builtin, this macro fails if MACRO is not
     defined.  Use

          m4_ifdef([MACRO], [m4_undefine([MACRO])])

     to recover the behavior of the builtin.

 - Macro: m4_bpatsubst (STRING, REGEXP, [REPLACEMENT])
     This macro corresponds to `patsubst'.  The name `m4_patsubst' is
     kept for future versions of M4sh, on top of GNU M4 which will
     provide extended regular expression syntax via `epatsubst'.

 - Macro: m4_popdef (MACRO)
     Contrary to the M4 builtin, this macro fails if MACRO is not
     defined.  See `m4_undefine'.

 - Macro: m4_bregexp (STRING, REGEXP, [REPLACEMENT])
     This macro corresponds to `regexp'.  The name `m4_regexp' is kept
     for future versions of M4sh, on top of GNU M4 which will provide
     extended regular expression syntax via `eregexp'.

 - Macro: m4_wrap (TEXT)
     This macro corresponds to `m4wrap'.

     You are encouraged to end TEXT with `[]', so that there are no
     risks that two consecutive invocations of `m4_wrap' result in an
     unexpected pasting of tokens, as in

          m4_define([foo], [Foo])
          m4_define([bar], [Bar])
          m4_define([foobar], [FOOBAR])
          m4_wrap([bar])
          m4_wrap([foo])
          =>FOOBAR