Fix UNALIGNED_OK logic, add autoconf rule to detect for non-Windows builds and default to UNALIGNED_OK=1

5 files changed, 100 insertions, 30 deletions

diff --git a/xdelta3/config.h.in b/xdelta3/config.h.in
index 220915d..f01f64a 100644
--- a/xdelta3/config.h.in
+++ b/xdelta3/config.h.in
@@ -1,5 +1,8 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* Define if pointers to integers require aligned access */
+#undef HAVE_ALIGNED_ACCESS_REQUIRED
+
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
diff --git a/xdelta3/configure.ac b/xdelta3/configure.ac
index 869f3c2..394e2ae 100644
--- a/xdelta3/configure.ac
+++ b/xdelta3/configure.ac
@@ -5,6 +5,7 @@ AC_CONFIG_MACRO_DIR([m4])
 #LT_INIT
 AM_INIT_AUTOMAKE([1.9 no-define foreign tar-ustar])
 #AC_DISABLE_STATIC
+AX_CHECK_ALIGNED_ACCESS_REQUIRED
 AC_PROG_CC
 AC_PROG_CXX
 AC_CHECK_HEADERS([lzma.h])
diff --git a/xdelta3/m4/ax_check_aligned_access_required.m4 b/xdelta3/m4/ax_check_aligned_access_required.m4
new file mode 100644
index 0000000..b078275
--- /dev/null
+++ b/xdelta3/m4/ax_check_aligned_access_required.m4
@@ -0,0 +1,84 @@
+# ====================================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_check_aligned_access_required.html
+# ====================================================================================
+#
+# SYNOPSIS
+#
+#   AC_CHECK_ALIGNED_ACCESS_REQUIRED
+#
+# DESCRIPTION
+#
+#   While the x86 CPUs allow access to memory objects to be unaligned it
+#   happens that most of the modern designs require objects to be aligned -
+#   or they will fail with a buserror. That mode is quite known by
+#   big-endian machines (sparc, etc) however the alpha cpu is little-
+#   endian.
+#
+#   The following function will test for aligned access to be required and
+#   set a config.h define HAVE_ALIGNED_ACCESS_REQUIRED (name derived by
+#   standard usage). Structures loaded from a file (or mmapped to memory)
+#   should be accessed per-byte in that case to avoid segfault type errors.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#
+#   This program is free software; you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation; either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 7
+
+AC_DEFUN([AX_CHECK_ALIGNED_ACCESS_REQUIRED],
+[AC_CACHE_CHECK([if pointers to integers require aligned access],
+  [ax_cv_have_aligned_access_required],
+  [AC_TRY_RUN([
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+  char* string = malloc(40);
+  int i;
+  for (i=0; i < 40; i++) string[[i]] = i;
+  {
+     void* s = string;
+     int* p = s+1;
+     int* q = s+2;
+
+     if (*p == *q) { return 1; }
+  }
+  return 0;
+}
+              ],
+     [ax_cv_have_aligned_access_required=yes],
+     [ax_cv_have_aligned_access_required=no],
+     [ax_cv_have_aligned_access_required=no])
+  ])
+if test "$ax_cv_have_aligned_access_required" = yes ; then
+  AC_DEFINE([HAVE_ALIGNED_ACCESS_REQUIRED], [1],
+    [Define if pointers to integers require aligned access])
+fi
+])
diff --git a/xdelta3/xdelta3-hash.h b/xdelta3/xdelta3-hash.h
index e546d59..08d8136 100644
--- a/xdelta3/xdelta3-hash.h
+++ b/xdelta3/xdelta3-hash.h
@@ -65,46 +65,29 @@ xd3_large_cksum_update (uint32_t cksum,
 /* TODO: revisit this topic */
 #endif
 
-/* Note: small cksum is hard-coded for 4 bytes */
 #if UNALIGNED_OK
-static inline uint32_t
-xd3_scksum (uint32_t *state,
-            const uint8_t *base,
-            const usize_t look)
-{
-  (*state) = *(uint32_t*)base;
-  return (*state) * hash_multiplier;
-}
-static inline uint32_t
-xd3_small_cksum_update (uint32_t *state,
-                        const uint8_t *base,
-                        usize_t look)
-{
-  (*state) = *(uint32_t*)(base+1);
-  return (*state) * hash_multiplier;
-}
+#define UNALIGNED_READ32(dest,src) (*(dest)) = (*(uint32_t*)(src))
 #else
+#define UNALIGNED_READ32(dest,src) memcpy((dest), (src), 4);
+#endif
+
+/* TODO: small cksum is hard-coded for 4 bytes (i.e., "look" is unused) */
 static inline uint32_t
 xd3_scksum (uint32_t *state,
             const uint8_t *base,
             const usize_t look)
 {
-  (*state) = (base[0] << 24 |
-              base[1] << 16 |
-              base[2] << 8 |
-              base[3]);
+  UNALIGNED_READ32(state, base);
   return (*state) * hash_multiplier;
 }
 static inline uint32_t
 xd3_small_cksum_update (uint32_t *state,
                         const uint8_t *base,
-                        const usize_t look)
+                        usize_t look)
 {
-  (*state) <<= 8;
-  (*state) |= base[4];
+  UNALIGNED_READ32(state, base+1);
   return (*state) * hash_multiplier;
 }
-#endif
 
 /***********************************************************************
  Ctable stuff
diff --git a/xdelta3/xdelta3.h b/xdelta3/xdelta3.h
index 6256961..0710f08 100644
--- a/xdelta3/xdelta3.h
+++ b/xdelta3/xdelta3.h
@@ -171,13 +171,12 @@ typedef uint32_t xoff_t;
 #define USE_UINT64 (SIZEOF_USIZE_T == 8 || \
                     SIZEOF_XOFF_T == 8 || REGRESSION_TEST)
 
-/* TODO: probably should do something better here. */
 #ifndef UNALIGNED_OK
-#if defined(__i386__) || defined(__i486__) || defined(__i586__) || \
-  defined(__i686__) || defined(_X86_) || defined(__x86_64__)
-#define UNALIGNED_OK 1
-#else
+#ifdef HAVE_ALIGNED_ACCESS_REQUIRED
 #define UNALIGNED_OK 0
+#else
+/* This generally includes all Windows builds. */
+#define UNALIGNED_OK 1
 #endif
 #endif