m4 quoting change? (2.52->2.53)

[Roger Leigh]

One of my custom m4 macros breaks with autoconf 2.53, which worked from
2.50 to 2.52:

[autogen.sh]
Running autoheader...
autoheader: warning: `configure.ac' and `configure.in' both present.
 at /usr/local/pkg/autoconf/bin/autoheader line 110
autoheader: warning: proceeding with `configure.ac'.
 at /usr/local/pkg/autoconf/bin/autoheader line 110
configure.ac:557: /usr/bin/m4: Bad regular expression: `test
"${CACHE[]_cflags+set}" = set': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_cflags': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_cflags': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression: `test
"${CACHE[]_libs+set}" = set': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_libs': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_libs': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression: `test
"${CACHE[]_version+set}" = set': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_version': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_version': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression: `test
"${CACHE[]_present+set}" = set': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_present': Unmatched [ or [^
configure.ac:557: /usr/bin/m4: Bad regular expression:
`$CACHE[]_present': Unmatched [ or [^
autoheader: `include/config.h.in' is unchanged

Running autoheader for a second time does not generate these
warnings--is this autom4te?

The code in question is quite simple:
  m4_pushdef([DOWN], m4_translit([$1], [A-Z], [a-z]))dnl
  m4_pushdef([CACHE], ac_cv_path_lib_[]DOWN)dnl
then
  AC_CACHE_CHECK([for UP CFLAGS],
                 [CACHE[]_cflags],
                 [CACHE[]_cflags=`$UP[]_CONFIG $LDOWN[]_config_args \
                                  LIBCONFIG_CFLAGS`])

All four sets (cflags, libs, version, present) of three warnings are
within AC_CACHE_CHECK macros. The [] is to separate the macro to be
expanded from the shell variable suffix.

The errors seem wrong--the `[' and `]' are /not/ unmatched at all!  I
didn't see anything relating to this specifically in the NEWS file.
What should I be doing differently?


Another question is upgrading between different versions of autoconf.
Are there any version-specific macros I can use to cater for use with
incompatible versions of automake? (In m4 macros, not configure.ac.)


Thanks,
Roger

-- 
Roger Leigh
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