Revise memutils.h to use alignment information gathered by

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

1 files changed, 64 insertions, 0 deletions

diff --git a/src/configure.in b/src/configure.in
index 091346153e4..92ff0135385 100644
--- a/src/configure.in
+++ b/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