eliminating SCM_POINTERS_MUNGED

[Dirk Herrmann <dirk at ida dot ing dot tu-bs dot de>]

Hi!

I have removed a little bit of sick code from gc.c.  The point is, that
whenever SCM2PTR and PTR2SCM are nontrivial, SCM_POINTERS_MUNGED is
defined.  However, SCM_POINTERS_MUNGED is used in a way that basically
duplicates the definition of PTR2SCM.

I will explain the patch using the following example.  I added the
comments after ////

scm_gc_sweep ()
{
  register SCM_CELLPTR ptr;
#ifdef SCM_POINTERS_MUNGED       //// i. e. PTR2SCM non trivial
  register SCM scmptr;
#else                            //// else  PTR2SCM trivial anyway
#undef scmptr
#define scmptr (SCM)ptr          //// but still duplicated (sick)
#endif
  register SCM nfreelist;
  register scm_freelist_t *freelist;
  register long m;


...


      seg_size = CELL_DN (scm_heap_table[i].bounds[1], span) - ptr;
      for (j = seg_size + span; j -= span; ptr += span)
       {
#ifdef SCM_POINTERS_MUNGED            //// PTR2SCM non trivial
         scmptr = PTR2SCM (ptr);
#endif
         switch SCM_TYP7 (scmptr)     //// ****
           {
           case scm_tcs_cons_gloc:

at places that use scmptr, like ***, we use either (SCM)ptr if
SCM_POINTERS_MUNGED is not defined.  However, in that case PTR2SCM would
have been defined to do exactly the same thing:  just cast to (SCM)

The same 'trick' is used a second time in gc.c.

Thus, the patch below should be safe.  If you don't object I will apply it and
then also remove SCM_POINTERS_MUNGED from tags.h

Best regards
Dirk Herrmann




Index: gc.c
===================================================================
RCS file: /cvs/guile/guile/guile-core/libguile/gc.c,v
retrieving revision 1.112
diff -u -r1.112 gc.c
--- gc.c	2000/03/23 13:04:27	1.112
+++ gc.c	2000/03/24 16:17:19
@@ -1587,12 +1587,6 @@
 scm_gc_sweep ()
 {
   register SCM_CELLPTR ptr;
-#ifdef SCM_POINTERS_MUNGED
-  register SCM scmptr;
-#else
-#undef scmptr
-#define scmptr (SCM)ptr
-#endif
   register SCM nfreelist;
   register scm_freelist_t *freelist;
   register long m;
@@ -1638,9 +1632,8 @@
       seg_size = CELL_DN (scm_heap_table[i].bounds[1], span) - ptr;
       for (j = seg_size + span; j -= span; ptr += span)
 	{
-#ifdef SCM_POINTERS_MUNGED
-	  scmptr = PTR2SCM (ptr);
-#endif
+	  SCM scmptr = PTR2SCM (ptr);
+
 	  switch SCM_TYP7 (scmptr)
 	    {
 	    case scm_tcs_cons_gloc:
@@ -2161,12 +2154,6 @@
 init_heap_seg (SCM_CELLPTR seg_org, scm_sizet size, scm_freelist_t *freelist)
 {
   register SCM_CELLPTR ptr;
-#ifdef SCM_POINTERS_MUNGED
-  register SCM scmptr;
-#else
-#undef scmptr
-#define scmptr ptr
-#endif
   SCM_CELLPTR seg_end;
   int new_seg_index;
   int n_new_cells;
@@ -2246,9 +2233,8 @@
 
 	while (ptr < seg_end)
 	  {
-#ifdef SCM_POINTERS_MUNGED
-	    scmptr = PTR2SCM (ptr);
-#endif
+	    SCM scmptr = PTR2SCM (ptr);
+
 	    SCM_SETCAR (scmptr, scm_tc_free_cell);
 	    SCM_SETCDR (scmptr, PTR2SCM (ptr + span));
 	    ptr += span;
@@ -2270,9 +2256,8 @@
    */
   while (ptr < seg_end)
     {
-#ifdef SCM_POINTERS_MUNGED
-      scmptr = PTR2SCM (ptr);
-#endif
+      SCM scmptr = PTR2SCM (ptr);
+
       SCM_SETCAR (scmptr, (SCM) scm_tc_free_cell);
       SCM_SETCDR (scmptr, PTR2SCM (ptr + span));
       ptr += span;
@@ -2294,9 +2279,6 @@
   fprintf (stderr, "H");
 #endif
   return size;
-#ifdef scmptr
-#undef scmptr
-#endif
 }
 
 #ifndef GUILE_NEW_GC_SCHEME