vm/local_roots.h

   1 /* If a runtime function needs to call another function which potentially
   2 allocates memory, it must store any local variable references to Factor
   3 objects on the root stack */
   4
   5 /* GC locals: stores addresses of pointers to objects. The GC updates these
   6 pointers, so you can do
   7
   8 REGISTER_ROOT(some_local);
   9
  10 ... allocate memory ...
  11
  12 foo(some_local);
  13
  14 ...
  15
  16 UNREGISTER_ROOT(some_local); */
  17 F_SEGMENT *gc_locals_region;
  18 CELL gc_locals;
  19
  20 DEFPUSHPOP(gc_local_,gc_locals)
  21
  22 #define REGISTER_ROOT(obj) gc_local_push((CELL)&obj)
  23 #define UNREGISTER_ROOT(obj) \
  24         { \
  25                 if(gc_local_pop() != (CELL)&obj) \
  26                         critical_error("Mismatched REGISTER_ROOT/UNREGISTER_ROOT",0); \
  27         }
  28
  29 /* Extra roots: stores pointers to objects in the heap. Requires extra work
  30 (you have to unregister before accessing the object) but more flexible. */
  31 F_SEGMENT *extra_roots_region;
  32 CELL extra_roots;
  33
  34 DEFPUSHPOP(root_,extra_roots)
  35
  36 #define REGISTER_UNTAGGED(obj) root_push(obj ? tag_object(obj) : 0)
  37 #define UNREGISTER_UNTAGGED(obj) obj = untag_object(root_pop())
  38
  39 /* We ignore strings which point outside the data heap, but we might be given
  40 a char* which points inside the data heap, in which case it is a root, for
  41 example if we call unbox_char_string() the result is placed in a byte array */
  42 INLINE bool root_push_alien(const void *ptr)
  43 {
  44         if(in_data_heap_p((CELL)ptr))
  45         {
  46                 F_BYTE_ARRAY *objptr = ((F_BYTE_ARRAY *)ptr) - 1;
  47                 if(objptr->header == tag_header(BYTE_ARRAY_TYPE))
  48                 {
  49                         root_push(tag_object(objptr));
  50                         return true;
  51                 }
  52         }
  53
  54         return false;
  55 }
  56
  57 #define REGISTER_C_STRING(obj) \
  58         bool obj##_root = root_push_alien(obj)
  59 #define UNREGISTER_C_STRING(obj) \
  60         if(obj##_root) obj = alien_offset(root_pop())
  61
  62 #define REGISTER_BIGNUM(obj) if(obj) root_push(tag_bignum(obj))
  63 #define UNREGISTER_BIGNUM(obj) if(obj) obj = (untag_object(root_pop()))