Allow the Windows build to use upto 2GB of heap.

 src/w32heap.c (allocate_heap) [USE_LISP_UNION_TYPE || USE_LSB_TAG]:
 New version that can reserve upto 2GB of heap space.
 etc/NEWS: Mention the new feature.

2 files changed, 29 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index b6f962f4523..42d9185e0dd 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2011-04-29  Eli Zaretskii  <eliz@gnu.org>
+
+        * w32heap.c (allocate_heap) [USE_LISP_UNION_TYPE || USE_LSB_TAG]:
+        New version that can reserve upto 2GB of heap space.
+
 2011-04-26  Chong Yidong  <cyd@stupidchicken.com>
 
         * nsfns.m (Fns_read_file_name): Doc fix (Bug#8534).
diff --git a/src/w32heap.c b/src/w32heap.c
index b5b18919a4a..91bc8133b20 100644
--- a/src/w32heap.c
+++ b/src/w32heap.c
@@ -119,6 +119,7 @@ get_data_end (void)
   return data_region_end;
 }
 
+#if !defined (USE_LISP_UNION_TYPE) && !defined (USE_LSB_TAG)
 static char *
 allocate_heap (void)
 {
@@ -145,9 +146,31 @@ allocate_heap (void)
 
   return ptr;
 }
+#else  /* USE_LISP_UNION_TYPE || USE_LSB_TAG */
+static char *
+allocate_heap (void)
+{
+  unsigned long size = 0x80000000; /* start by asking for 2GB */
+  void *ptr = NULL;
+
+  while (!ptr && size > 0x00100000)
+    {
+      reserved_heap_size = size;
+      ptr = VirtualAlloc (NULL,
+                          get_reserved_heap_size (),
+                          MEM_RESERVE,
+                          PAGE_NOACCESS);
+      size -= 0x00800000; /* if failed, decrease request by 8MB */
+    }
+
+  return ptr;
+}
+#endif /* USE_LISP_UNION_TYPE || USE_LSB_TAG */
 
 
-/* Emulate Unix sbrk.  */
+/* Emulate Unix sbrk.  Note that ralloc.c expects the return value to
+   be the address of the _start_ (not end) of the new block in case of
+   success, and zero (not -1) in case of failure.  */
 void *
 sbrk (unsigned long increment)
 {