3 files changed, 80 insertions, 4 deletions

diff --git a/configure b/configure
index ef489af5..34be9b59 100755
--- a/configure
+++ b/configure
@@ -2675,6 +2675,44 @@ if [ -z "$have_alloca" ] ; then
   exit 1
 fi
 
+printf "Checking for malloc-with-alignment function ... "
+
+while true ; do
+  cat > conftest.c <<!
+#include <malloc.h>
+
+int main(void)
+{
+  void *bytes = memalign(16, 42);
+  return 0;
+}
+!
+
+  if ! conftest ; then
+    printf "memalign\n"
+    printf "#define HAVE_MEMALIGN 1\n" $try_header >> config.h
+    break;
+  fi
+
+  cat > conftest.c <<!
+#include <stdlib.h>
+
+int main(void)
+{
+  void *bytes;
+  int res = posix_memalign(&bytes, 16, 42);
+  return 0;
+}
+!
+  if conftest ; then
+    printf "posix_memalign\n"
+    printf "#define HAVE_POSIX_MEMALIGN 1\n" $try_header >> config.h
+    break;
+  fi
+
+  printf "none\n"
+done
+
 printf "Checking for termios ... "
 
 cat > conftest.c <<!
diff --git a/gc.c b/gc.c
index 1b3e68cd..93004338 100644
--- a/gc.c
+++ b/gc.c
@@ -57,9 +57,15 @@
 #define STACK_TOP_EXTRA_WORDS 0
 #endif
 
+#if HAVE_MEMALIGN || HAVE_POSIX_MEMALIGN
+#define OBJ_ALIGN (sizeof (obj_t))
+#else
+#define OBJ_ALIGN 8
+#endif
+
 typedef struct heap {
-  struct heap *next;
   obj_t block[HEAP_SIZE];
+  struct heap *next;
 } heap_t;
 
 typedef struct mach_context {
@@ -427,13 +433,22 @@ static int in_heap(val ptr)
   if (!is_ptr(ptr))
     return 0;
 
+  if (coerce(uint_ptr_t, ptr) % OBJ_ALIGN != 0)
+    return 0;
+
   if (ptr < heap_min_bound || ptr >= heap_max_bound)
     return 0;
 
   for (heap = heap_list; heap != 0; heap = heap->next) {
-    if (ptr >= heap->block && ptr < heap->block + HEAP_SIZE)
-      if ((coerce(char *, ptr) - coerce(char *, heap->block)) % sizeof (obj_t) == 0)
+    if (ptr >= heap->block && ptr < heap->block + HEAP_SIZE) {
+#if HAVE_MEMALIGN || HAVE_POSIX_MEMALIGN
+      return 1;
+#else
+      if ((coerce(char *, ptr) -
+           coerce(char *, heap->block)) % sizeof (obj_t) == 0)
         return 1;
+#endif
+    }
   }
 
   return 0;
diff --git a/lib.c b/lib.c
index debd353f..f4f47b76 100644
--- a/lib.c
+++ b/lib.c
@@ -45,6 +45,9 @@
 #define NOMINMAX
 #include <windows.h>
 #endif
+#if HAVE_MEMALIGN
+#include <malloc.h>
+#endif
 #include "lib.h"
 #include "gc.h"
 #include "arith.h"
@@ -2849,9 +2852,29 @@ mem_t *chk_malloc(size_t size)
   return ptr;
 }
 
+#if HAVE_POSIX_MEMALIGN
+
+static void *memalign(size_t align, size_t size)
+{
+  void *ptr;
+  if (posix_memalign(&ptr, align, size) == 0)
+    return ptr;
+  return 0;
+}
+
+#elif !HAVE_MEMALIGN
+
+static void *memalign(size_t align, size_t size)
+{
+  (void) align;
+  return malloc(size);
+}
+
+#endif
+
 mem_t *chk_malloc_gc_more(size_t size)
 {
-  mem_t *ptr = convert(mem_t *, malloc(size));
+  mem_t *ptr = convert(mem_t *, memalign(sizeof (obj_t), size));
   assert (!async_sig_enabled);
   if (size && ptr == 0)
     oom();