Change type of size arguments of GC_register_altstack from word to si…

…ze_t

Issue #627 (bdwgc).

* include/gc/gc.h [GC_THREADS] (GC_register_altstack): Change type of
normstack_size and altstack_size arguments from GC_word to size_t.
* pthread_support.c [!GC_WIN32_THREADS] (GC_register_altstack):
Likewise.
* include/private/pthread_support.h [!GC_WIN32_THREADS]
(GC_StackContext_Rep): Reorder normstack and altstack_size fields.
* include/private/pthread_support.h [!GC_WIN32_THREADS]
(GC_StackContext_Rep.altstack_size, GC_StackContext_Rep.normstack):
Change type from word to size_t.

include/gc/gc.h

@@ -1740,9 +1740,9 @@ GC_API void GC_CALL GC_start_mark_threads(void);
   /* while it is on an alt-stack.  Acquires the allocator lock in the   */
   /* reader mode.                                                       */
   GC_API void GC_CALL GC_register_altstack(void * /* normstack */,
-                                           GC_word /* normstack_size */,
+                                           size_t /* normstack_size */,
                                            void * /* altstack */,
-                                           GC_word /* altstack_size */);
+                                           size_t /* altstack_size */);
 
   /* Unregister the current thread.  Only an explicitly registered      */
   /* thread (i.e. for which GC_register_my_thread() returns GC_SUCCESS) */

include/private/pthread_support.h

@@ -89,10 +89,10 @@ typedef struct GC_StackContext_Rep {
 # else
     ptr_t altstack;             /* The start of the alt-stack if there  */
                                 /* is one, NULL otherwise.              */
-    word altstack_size;         /* The size of the alt-stack if exists. */
-    ptr_t normstack;            /* The start and size of the "normal"   */
-                                /* stack (set by GC_register_altstack). */
-    word normstack_size;
+    ptr_t normstack;            /* Same for the "normal" stack (set by  */
+                                /* GC_register_altstack).               */
+    size_t altstack_size;       /* The size of the alt-stack if exists. */
+    size_t normstack_size;
 # endif
 
 # ifdef E2K

pthread_support.c

@@ -932,7 +932,8 @@ GC_API int GC_CALL GC_thread_is_registered(void)
 }
 
 GC_API void GC_CALL GC_register_altstack(void *normstack,
-                GC_word normstack_size, void *altstack, GC_word altstack_size)
+                                         size_t normstack_size,
+                                         void *altstack, size_t altstack_size)
 {
 #ifdef GC_WIN32_THREADS
   /* TODO: Implement */