more small tweaks to the layout optimization PR (JuliaLang#34177)

- fix GC/finalizer properties of CFunction definition
- fix jl_arrayunset implementation for hasptr
- fix missing GC metadata update step inside gc_mark_scan_array8

base/c.jl

@@ -26,7 +26,7 @@ and will be converted automatically at the call site to the appropriate type.
 
 See [`@cfunction`](@ref).
 """
-struct CFunction <: Ref{Cvoid}
+mutable struct CFunction <: Ref{Cvoid}
  ptr::Ptr{Cvoid}
  f::Any
  _1::Ptr{Cvoid}

src/array.c

@@ -619,7 +619,7 @@ JL_DLLEXPORT void jl_arrayunset(jl_array_t *a, size_t i)
  else if (a->flags.hasptr) {
  size_t elsize = a->elsize;
  jl_assume(elsize >= sizeof(void*) && elsize % sizeof(void*) == 0);
- memset(&((jl_value_t**)a->data)[i], 0, elsize);
+ memset((char*)a->data + elsize * i, 0, elsize);
  }
 }
 

src/gc.c

@@ -1794,6 +1794,7 @@ STATIC_INLINE int gc_mark_scan_array8(jl_ptls_t ptls, jl_gc_mark_sp_t *sp,
  if (elem_begin < elem_end) {
  // Haven't done with this one yet. Update the content and push it back
  ary8->elem.begin = elem_begin;
+ ary8->begin = begin;
  gc_repush_markdata(sp, gc_mark_array8_t);
  }
  else {
@@ -1812,7 +1813,7 @@ STATIC_INLINE int gc_mark_scan_array8(jl_ptls_t ptls, jl_gc_mark_sp_t *sp,
  }
  return 1;
  }
- ary8->elem.begin = elem_begin = ary8->rebegin;
+ elem_begin = ary8->rebegin;
  }
  gc_mark_push_remset(ptls, ary8->elem.parent, ary8->elem.nptr);
  return 0;