+
+dnl ** figure out the alignment restriction of a type
+dnl (required SIZEOF test but AC_CHECK_SIZEOF doesn't call PROVIDE
+dnl so we can't call REQUIRE)
+
+dnl GHC_CHECK_ALIGNMENT(TYPE)
+AC_DEFUN(GHC_CHECK_ALIGNMENT,
+[changequote(<<, >>)dnl
+dnl The name to #define.
+define(<<AC_TYPE_NAME>>, translit(alignment_$1, [a-z *], [A-Z_P]))dnl
+dnl The cache variable name.
+define(<<AC_CV_NAME>>, translit(ac_cv_alignment_$1, [ *], [_p]))dnl
+dnl The name of the corresponding size.
+define(<<AC_CV_SIZEOF_NAME>>, translit(ac_cv_sizeof_$1, [ *], [_p]))dnl
+changequote([, ])dnl
+AC_MSG_CHECKING(alignment of $1)
+AC_CACHE_VAL(AC_CV_NAME,
+[AC_TRY_RUN([
+#include <stdio.h>
+#if HAVE_STDDEF_H
+#include <stddef.h>
+#endif
+#ifndef offsetof
+#define offsetof(ty,field) ((size_t)((char *)&((ty *)0)->field - (char *)(ty *)0))
+#endif
+int
+main()
+{
+ FILE *f=fopen("conftestval", "w");
+ if (!f) exit(1);
+ fprintf(f, "%d\n", offsetof(struct { char c; $1 ty;},ty));
+ exit(0);
+}],
+AC_CV_NAME=`cat conftestval`,
+AC_CV_NAME=$AC_CV_SIZEOF_NAME,
+AC_CV_NAME=$AC_CV_SIZEOF_NAME)])
+AC_MSG_RESULT($AC_CV_NAME)
+AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME)
+AC_PROVIDE($AC_TYPE_NAME)
+undefine([AC_TYPE_NAME])dnl
+undefine([AC_CV_NAME])dnl
+undefine([AC_CV_SIZEOF_NAME])dnl
+])
+