Cleanup mark-during-GC debug checks.

* libguile/__scm.h (SCM_DEBUG): add SCM_DEBUG_MARKING_API

* libguile/gc.h (SCM_SET_GC_MARK): depending on
SCM_DEBUG_MARKING_API crash if someone is touching markbits
outside regular hours.

Rename ensure_marking() to scm_i_ensure_marking().

* libguile/inline.h (scm_double_cell, scm_cell): only set mark bits
for debugging if SCM_DEBUG_MARKING_API is unset

* libguile/gc-mark.c: Issue deprecation warning if we are marking
outside of the GC mark phase.

libguile/__scm.h

@@ -197,6 +197,14 @@
 #define SCM_DEBUG 0
 #endif
 
+/* For debugging purposes: define this is to ensure nobody is using
+ * the mark bits outside of the marking phase.  This is meant for
+ * debugging purposes only.
+ */
+#ifndef SCM_DEBUG_MARKING_API
+#define SCM_DEBUG_MARKING_API 0
+#endif
+
 /* If SCM_DEBUG_CELL_ACCESSES is set to 1, cell accesses will perform
  * exhaustive parameter checking:  It will be verified that cell parameters
  * actually point to a valid heap cell.  Note:  If this option is enabled,

libguile/gc-mark.c

@@ -165,12 +165,19 @@ scm_gc_mark (SCM ptr)
   if (SCM_GC_MARK_P (ptr))
     return;
 
+  if (!scm_i_marking)
+    {
+      static const char msg[]
+	= "Should only call scm_gc_mark() during GC.";
+      scm_c_issue_deprecation_warning (msg);
+    }
+
   SCM_SET_GC_MARK (ptr);
   scm_gc_mark_dependencies (ptr);
 }
 
 void
-ensure_marking (void)
+scm_i_ensure_marking (void)
 {
   assert (scm_i_marking);
 }

libguile/gc.c

@@ -143,7 +143,7 @@ scm_assert_cell_valid (SCM cell)
       */
       if (scm_expensive_debug_cell_accesses_p)
 	scm_i_expensive_validation_check (cell);
-      
+#if (SCM_DEBUG_MARKING_API == 0)
       if (!SCM_GC_MARK_P (cell))
 	{
 	  fprintf (stderr,
@@ -153,7 +153,8 @@ scm_assert_cell_valid (SCM cell)
                    (unsigned long) SCM_UNPACK (cell));
 	  abort ();
 	}
-
+#endif /* SCM_DEBUG_MARKING_API */
+      
       scm_i_cell_validation_already_running = 0;  /* re-enable */
     }
 }

libguile/gc.h

@@ -156,9 +156,16 @@ typedef unsigned long scm_t_c_bvec_long;
 /* testing and changing GC marks */
 #define SCM_GC_MARK_P(x)   SCM_GC_CELL_GET_BIT (x)
 
-void ensure_marking(void);
+SCM_INTERNAL void scm_i_ensure_marking(void);
-#define SCM_SET_GC_MARK(x) SCM_GC_CELL_SET_BIT (x)
+
-#define SCM_CLEAR_GC_MARK(x) SCM_GC_CELL_CLEAR_BIT (x)
+#if (SCM_DEBUG_MARKING_API == 1)
+#define SCM_I_ENSURE_MARKING scm_i_ensure_marking(), 
+#else
+#define SCM_I_ENSURE_MARKING
+#endif
+
+#define SCM_SET_GC_MARK(x) SCM_I_ENSURE_MARKING SCM_GC_CELL_SET_BIT (x)
+#define SCM_CLEAR_GC_MARK(x) SCM_I_ENSURE_MARKING SCM_GC_CELL_CLEAR_BIT (x)
 
 /* Low level cell data accessing macros.  These macros should only be used
  * from within code related to garbage collection issues, since they will

libguile/inline.h

@@ -134,12 +134,14 @@ scm_cell (scm_t_bits car, scm_t_bits cdr)
 	  }
       }
 
+#if (SCM_DEBUG_MARKING_API == 0)
     /*
       Always set mark. Otherwise cells that are alloced before
       scm_debug_cell_accesses_p is toggled seem invalid.
     */
     SCM_SET_GC_MARK (z);
-
+#endif /* SCM_DEBUG_MARKING_API */
+    
     /*
       TODO: figure out if this use of mark bits is valid with
       threading. What if another thread is doing GC at this point
@@ -202,10 +204,11 @@ scm_double_cell (scm_t_bits car, scm_t_bits cbr,
 	  abort();
 	}
     }
-
+#if (SCM_DEBUG_MARKING_API == 0)
   /* see above. */
   SCM_SET_GC_MARK (z);
-
+#endif /* SCM_DEBUG_MARKING_API */
+  
 #endif
 
   /* When this function is inlined, it's possible that the last