From b3ee9cdddd521d0ee87a114269fc683f93d215e0 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Wed, 30 Nov 2011 14:15:28 -0800
Subject: * configure (extra_debugging): New variable. EXTRA_DEBUGGING
 conditionally generated in config.h.

* gc.c (break_obj): New static variable.
(mark_obj): Debugging feature: if the object is the one stored in
break_obj and not yet reached, then call breakpt.
(deheap): New debugging function for viewing regions of the heaps.

* lib.c (breakpt): New function.

* lib.h (breakpt): Declared.
---
 ChangeLog | 14 ++++++++++++++
 configure | 15 +++++++++++++++
 gc.c      | 18 ++++++++++++++++++
 lib.c     | 10 ++++++++++
 lib.h     |  1 +
 5 files changed, 58 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index e79a1d2d..94bebc0e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2011-11-30  Kaz Kylheku  <kaz@kylheku.com>
+
+	* configure (extra_debugging): New variable. EXTRA_DEBUGGING
+	conditionally generated in config.h.
+
+	* gc.c (break_obj): New static variable.
+	(mark_obj): Debugging feature: if the object is the one stored in
+	break_obj and not yet reached, then call breakpt.
+	(deheap): New debugging function for viewing regions of the heaps.
+
+	* lib.c (breakpt): New function.
+
+	* lib.h (breakpt): Declared.
+
 2011-11-30  Kaz Kylheku  <kaz@kylheku.com>
 
 	* hash.c (hash_process_weak): Fix regression caused by a mistake
diff --git a/configure b/configure
index 2b012c43..6255fc9a 100755
--- a/configure
+++ b/configure
@@ -135,6 +135,7 @@ lex_dbg_flags=${lex_dbg_flags-}
 txr_dbg_opts=${txr_dbg_opts---gc-debug}
 valgrind=${valgrind-}
 lit_align=${lit_align-}
+extra_debugging=${extra_debugging-}
 
 #
 # If --help was given (or --help=<nonempty> or help=<nonempty>) then
@@ -334,6 +335,11 @@ valgrind [$valgrind]
   Valgrind integration means that when the program is running under valgrind,
   it advises valgrind about stack memory locations accessed by the garbage
   collector, to suppress diagnostics about uninitialized accesses.
+
+extra_debugging [$extra_debugging]
+
+  Use --extra_debugging to configure some additional debugging features,
+  which incur a run-time penalty.
 !
   exit 1
 fi
@@ -921,6 +927,15 @@ else
   printf "#define HAVE_GETENVIRONMENTSTRINGS 1\n" >> config.h
 fi
 
+#
+# Extra debugging.
+#
+
+if [ -n "$extra_debugging" ] ; then
+  printf "Configuring extra debugging, as requested ...\n"
+  printf "#define EXTRA_DEBUGGING 1\n" >> config.h
+fi
+
 #
 # Clean up
 #
diff --git a/gc.c b/gc.c
index 4f8c41bc..72b1af05 100644
--- a/gc.c
+++ b/gc.c
@@ -72,6 +72,10 @@ static val heap_min_bound, heap_max_bound;
 
 int gc_enabled = 1;
 
+#if EXTRA_DEBUGGING
+static val break_obj;
+#endif
+
 val prot1(val *loc)
 {
   assert (top < prot_stack_limit);
@@ -243,6 +247,11 @@ tail_call:
 
   obj->t.type = (type_t) (obj->t.type | REACHABLE);
 
+#if EXTRA_DEBUGGING
+  if (obj == break_obj)
+    breakpt();
+#endif
+
   switch (t) {
   case CONS:
     mark_obj(obj->c.car);
@@ -512,6 +521,15 @@ void unmark(void)
   }
 }
 
+void dheap(heap_t *heap, int start, int end);
+
+void dheap(heap_t *heap, int start, int end)
+{
+  int i;
+  for (i = start; i < end; i++)
+    format(std_output, lit("(~a ~s)\n"), num(i), &heap->block[i], nao);
+}
+
 /*
  * This function does nothing.
  * gc_hint(x) just takes the address of local variable x
diff --git a/lib.c b/lib.c
index fdf5758e..a605a556 100644
--- a/lib.c
+++ b/lib.c
@@ -3228,3 +3228,13 @@ void d(val obj)
 {
   dump(obj, std_output);
 }
+
+/*
+ * Function for software breakpoints.
+ * Debugging routines call here when a breakpoint
+ * is requested. For this to work, set a breakpoint
+ * on this function.
+ */
+void breakpt(void)
+{
+}
diff --git a/lib.h b/lib.h
index 732c5eb8..47cb414e 100644
--- a/lib.h
+++ b/lib.h
@@ -495,6 +495,7 @@ void init(const wchar_t *progname, mem_t *(*oom_realloc)(mem_t *, size_t),
           val *stack_bottom);
 void dump(val obj, val stream);
 void d(val obj);
+void breakpt(void);
 
 #define nil ((obj_t *) 0)
 
-- 
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