autoheader produces files which choke configure

[Sam Steingold]

configure.in:
AC_FUNC_ALLOCA

==> config.h.in:
/* Define to 1 if you have <alloca.h> and it should be used (not on Ultrix).
   */
#undef HAVE_ALLOCA_H

$ bash -x -n configure
==>
modules/regexp/config.h.in: line 14: syntax error near unexpected token `('
modules/regexp/config.h.in: line 14: `/* Define to 1 if you have <alloca.h> and 
 it should be used (not on Ultrix).'

what am I missing?

-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
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