Fix static assert violation in GC_calloc_prepare_explicitly_typed on …

…CHERI

(fix of commit 433e2dd)

Issue #627 (bdwgc).

* include/gc/gc_typed.h [!GC_BUILD] (GC_calloc_typed_descr_s): First
define it as a macro (referring to GC_calloc_typed_descr_opaque_s).
* include/gc/gc_typed.h (GC_calloc_typed_descr_s): Undefine (after
definition of struct GC_calloc_typed_descr_s.
* typd_mlc.c (GC_calloc_prepare_explicitly_typed): Compare sizeof
GC_calloc_typed_descr_s to that of GC_calloc_typed_descr_opaque_s in
static assert (instead of computing the struct size using
GC_CALLOC_TYPED_DESCR_PTRS and GC_CALLOC_TYPED_DESCR_WORDS).

include/gc/gc_typed.h

@@ -119,12 +119,14 @@ GC_API GC_ATTR_MALLOC GC_ATTR_CALLOC_SIZE(1, 2) void *GC_CALL
 
 #ifdef GC_BUILD
 struct GC_calloc_typed_descr_s;
-#else
+#  define GC_calloc_typed_descr_s GC_calloc_typed_descr_opaque_s
+#endif
+
 struct GC_calloc_typed_descr_s {
   GC_uintptr_t opaque_p[GC_CALLOC_TYPED_DESCR_PTRS];
   GC_word opaque[GC_CALLOC_TYPED_DESCR_WORDS - GC_CALLOC_TYPED_DESCR_PTRS];
 };
-#endif
+#undef GC_calloc_typed_descr_s
 
 /* This is same as GC_calloc_explicitly_typed but more optimal  */
 /* in terms of the performance and memory usage if the client   */

typd_mlc.c

@@ -500,11 +500,8 @@ GC_calloc_prepare_explicitly_typed(struct GC_calloc_typed_descr_s *pctd,
                                    size_t ctd_sz, size_t n, size_t lb,
                                    GC_descr d)
 {
-  GC_STATIC_ASSERT(
-      sizeof(struct GC_calloc_typed_descr_s)
-      == GC_CALLOC_TYPED_DESCR_PTRS * sizeof(ptr_t)
-             + (GC_CALLOC_TYPED_DESCR_WORDS - GC_CALLOC_TYPED_DESCR_PTRS)
-                   * sizeof(word));
+  GC_STATIC_ASSERT(sizeof(struct GC_calloc_typed_descr_opaque_s)
+                   == sizeof(struct GC_calloc_typed_descr_s));
   GC_ASSERT(GC_explicit_typing_initialized);
   GC_ASSERT(sizeof(struct GC_calloc_typed_descr_s) == ctd_sz);
   (void)ctd_sz; /* unused currently */