Revise memutils.h to use alignment information gathered by

configure, instead of having a bunch of crufty platform-specific guesses.

src/configure.in

@@ -896,6 +896,70 @@ fi
 AC_DEFINE_UNQUOTED(INT64_FORMAT, $INT64_FORMAT)
 
 
+dnl Determine memory alignment requirements for the basic C datatypes.
+
+dnl CHECK_ALIGNOF(TYPE)
+dnl This is modeled on the standard autoconf macro AC_CHECK_SIZEOF,
+dnl except it finds the alignment requirement of the type instead of the size.
+dnl The defined symbol is named ALIGNOF_TYPE, where the type name is
+dnl converted in the same way as for AC_CHECK_SIZEOF.
+dnl If cross-compiling, sizeof(type) is used as a default assumption.
+
+AC_DEFUN(CHECK_ALIGNOF,
+[changequote(<<, >>)dnl
+dnl The name to #define.
+define(<<AC_TYPE_NAME>>, translit(alignof_$1, [a-z *], [A-Z_P]))dnl
+dnl The cache variable name.
+define(<<AC_CV_NAME>>, translit(ac_cv_alignof_$1, [ *], [_p]))dnl
+changequote([, ])dnl
+AC_MSG_CHECKING(alignment of $1)
+AC_CACHE_VAL(AC_CV_NAME,
+[AC_TRY_RUN([#include <stdio.h>
+struct { char filler; $1 field; } mystruct;
+main()
+{
+  FILE *f=fopen("conftestval", "w");
+  if (!f) exit(1);
+  fprintf(f, "%d\n", ((char*) & mystruct.field) - ((char*) & mystruct));
+  exit(0);
+}], AC_CV_NAME=`cat conftestval`,
+AC_CV_NAME='sizeof($1)',
+AC_CV_NAME='sizeof($1)')])dnl
+AC_MSG_RESULT($AC_CV_NAME)
+AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME)
+undefine([AC_TYPE_NAME])dnl
+undefine([AC_CV_NAME])dnl
+])
+
+CHECK_ALIGNOF(short)
+CHECK_ALIGNOF(int)
+CHECK_ALIGNOF(long)
+if [[ $HAVE_LONG_LONG_INT_64 -eq 1 ]] ; then
+  CHECK_ALIGNOF(long long int)
+fi
+CHECK_ALIGNOF(double)
+
+dnl Compute maximum alignment of any basic type.
+dnl We assume long's alignment is at least as strong as char, short, or int;
+dnl but we must check long long (if it exists) and double.
+
+if [[ $ac_cv_alignof_double != 'sizeof(double)' ]] ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long"
+  if [[ $MAX_ALIGNOF -lt $ac_cv_alignof_double ]] ; then
+    MAX_ALIGNOF="$ac_cv_alignof_double"
+  fi
+  if [[ $HAVE_LONG_LONG_INT_64 -eq 1 ]] ; then
+    if [[ $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ]] ; then
+      MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
+    fi
+  fi
+else
+  dnl cross-compiling: assume that double's alignment is worst case
+  MAX_ALIGNOF="$ac_cv_alignof_double"
+fi
+AC_DEFINE_UNQUOTED(MAXIMUM_ALIGNOF, $MAX_ALIGNOF)
+
+
 dnl Check to see if platform has POSIX signal interface.
 dnl NOTE: if this test fails then POSIX signals definitely don't work.
 dnl It could be that the test compiles but the POSIX routines don't

src/include/config.h.in

@@ -290,6 +290,18 @@ extern void srandom(unsigned int seed);
 /* Define this as the appropriate snprintf format for 64-bit ints, if any */
 #undef INT64_FORMAT
 
+/* These must be defined as the alignment requirement (NOT the size) of
+ * each of the basic C data types (except char, which we assume has align 1).
+ * MAXIMUM_ALIGNOF is the largest alignment requirement for any C data type.
+ * ALIGNOF_LONG_LONG_INT need only be defined if HAVE_LONG_LONG_INT_64 is.
+ */
+#undef ALIGNOF_SHORT
+#undef ALIGNOF_INT
+#undef ALIGNOF_LONG
+#undef ALIGNOF_LONG_LONG_INT
+#undef ALIGNOF_DOUBLE
+#undef MAXIMUM_ALIGNOF
+
 /* Define as the base type of the last arg to accept */
 #undef SOCKET_SIZE_TYPE
 

src/include/utils/memutils.h

@@ -15,7 +15,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: memutils.h,v 1.22 1999/03/25 03:49:34 tgl Exp $
+ * $Id: memutils.h,v 1.23 1999/03/25 19:05:19 tgl Exp $
  *
  * NOTES
  *	  some of the information in this file will be moved to
@@ -30,50 +30,21 @@
 /* ----------------
  * Alignment macros: align a length or address appropriately for a given type.
  *
- * It'd be best to use offsetof to check how the compiler aligns stuff,
- * but not all compilers support that (still true)?  So we make the
- * conservative assumption that a type must be aligned on a boundary equal
- * to its own size, except on a few architectures where we know better.
+ * There used to be some incredibly crufty platform-dependent hackery here,
+ * but now we rely on the configure script to get the info for us. Much nicer.
  *
- * CAUTION: for the system tables, the struct declarations found in
- * src/include/pg_*.h had better be interpreted by the compiler in a way
- * that agrees with the workings of these macros.  In practice that means
- * being careful to lay out the columns of a system table in a way that avoids
- * wasted pad space.
- *
- * CAUTION: _ALIGN will not work if sizeof(TYPE) is not a power of 2.
- * There are machines where sizeof(double) is not, for example.
- * But such a size is almost certainly not an alignment boundary anyway.
+ * NOTE: _ALIGN will not work if ALIGNVAL is not a power of 2.
+ * That case seems extremely unlikely to occur in practice, however.
  * ----------------
  */
 
-#define _ALIGN(TYPE,LEN) \
-		(((long)(LEN) + (sizeof(TYPE) - 1)) & ~(sizeof(TYPE) - 1))
-
-#define SHORTALIGN(LEN)			_ALIGN(short, (LEN))
-
-#if defined(m68k)
-#define INTALIGN(LEN)			_ALIGN(short, (LEN))
-#else
-#define INTALIGN(LEN)			_ALIGN(int, (LEN))
-#endif
-
-#if (defined(sun) && ! defined(sparc)) || defined(m68k)
-#define LONGALIGN(LEN)			_ALIGN(short, (LEN))
-#else
-#define LONGALIGN(LEN)			_ALIGN(long, (LEN))
-#endif
-
-#if defined(m68k)
-#define DOUBLEALIGN(LEN)		_ALIGN(short, (LEN))
-#define MAXALIGN(LEN)			_ALIGN(short, (LEN))
-#elif defined(sco)
-#define DOUBLEALIGN(LEN)		_ALIGN(int, (LEN))
-#define MAXALIGN(LEN)			_ALIGN(int, (LEN))
-#else
-#define DOUBLEALIGN(LEN)		_ALIGN(double, (LEN))
-#define MAXALIGN(LEN)			_ALIGN(double, (LEN))
-#endif
+#define _ALIGN(ALIGNVAL,LEN)	(((long)(LEN) + (ALIGNVAL-1)) & ~(ALIGNVAL-1))
+
+#define SHORTALIGN(LEN)			_ALIGN(ALIGNOF_SHORT, (LEN))
+#define INTALIGN(LEN)			_ALIGN(ALIGNOF_INT, (LEN))
+#define LONGALIGN(LEN)			_ALIGN(ALIGNOF_LONG, (LEN))
+#define DOUBLEALIGN(LEN)		_ALIGN(ALIGNOF_DOUBLE, (LEN))
+#define MAXALIGN(LEN)			_ALIGN(MAXIMUM_ALIGNOF, (LEN))
 
 /*****************************************************************************
  *	  oset.h --			Fixed format ordered set definitions.				 *