+dnl See whether we need a declaration for a function.
+dnl The result is highly dependent on the INCLUDES passed in, so make sure
+dnl to use a different cache variable name in this macro if it is invoked
+dnl in a different context somewhere else.
+dnl gcc_AC_CHECK_DECL(SYMBOL,
+dnl [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND [, INCLUDES]]])
+AC_DEFUN([gcc_AC_CHECK_DECL],
+[AC_MSG_CHECKING([whether $1 is declared])
+AC_CACHE_VAL(gcc_cv_have_decl_$1,
+[AC_TRY_COMPILE([$4],
+[#ifndef $1
+char *(*pfn) = (char *(*)) $1 ;
+#endif], eval "gcc_cv_have_decl_$1=yes", eval "gcc_cv_have_decl_$1=no")])
+if eval "test \"`echo '$gcc_cv_have_decl_'$1`\" = yes"; then
+ AC_MSG_RESULT(yes) ; ifelse([$2], , :, [$2])
+else
+ AC_MSG_RESULT(no) ; ifelse([$3], , :, [$3])
+fi
+])dnl
+
+dnl Check multiple functions to see whether each needs a declaration.
+dnl Arrange to define HAVE_DECL_<FUNCTION> to 0 or 1 as appropriate.
+dnl gcc_AC_CHECK_DECLS(SYMBOLS,
+dnl [ACTION-IF-NEEDED [, ACTION-IF-NOT-NEEDED [, INCLUDES]]])
+AC_DEFUN([gcc_AC_CHECK_DECLS],
+[for ac_func in $1
+do
+changequote(, )dnl
+ ac_tr_decl=HAVE_DECL_`echo $ac_func | tr 'abcdefghijklmnopqrstuvwxyz' 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'`
+changequote([, ])dnl
+gcc_AC_CHECK_DECL($ac_func,
+ [AC_DEFINE_UNQUOTED($ac_tr_decl, 1) $2],
+ [AC_DEFINE_UNQUOTED($ac_tr_decl, 0) $3],
+dnl It is possible that the include files passed in here are local headers
+dnl which supply a backup declaration for the relevant prototype based on
+dnl the definition of (or lack of) the HAVE_DECL_ macro. If so, this test
+dnl will always return success. E.g. see libiberty.h's handling of
+dnl `basename'. To avoid this, we define the relevant HAVE_DECL_ macro to
+dnl 1 so that any local headers used do not provide their own prototype
+dnl during this test.
+#undef $ac_tr_decl
+#define $ac_tr_decl 1
+ $4
+)
+done
+dnl Automatically generate config.h entries via autoheader.
+if test x = y ; then
+ patsubst(translit([$1], [a-z], [A-Z]), [\w+],
+ [AC_DEFINE([HAVE_DECL_\&], 1,
+ [Define to 1 if we found this declaration otherwise define to 0.])])dnl
+fi
+])
+