From 3ca7300a0dd8fde68bf551c587f911f4116034e2 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 2 Nov 2012 06:51:35 -0600
Subject: [PATCH] improvements to GC backtrace info

---
 src/racket/gc2/backtrace.c | 12 +++++++-----
 src/racket/gc2/newgc.c     | 19 +++++++++++++++++--
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/racket/gc2/backtrace.c b/src/racket/gc2/backtrace.c
index 7edaa15fde..dab7299429 100644
--- a/src/racket/gc2/backtrace.c
+++ b/src/racket/gc2/backtrace.c
@@ -39,14 +39,15 @@ static void register_traced_object(void *p)
 
 static void *print_out_pointer(const char *prefix, void *p,
 			       GC_get_type_name_proc get_type_name,
-			       GC_print_tagged_value_proc print_tagged_value)
+			       GC_print_tagged_value_proc print_tagged_value,
+                               int *_kind)
 {
   trace_page_t *page;
   const char *what;
 
   page = pagemap_find_page(GC_instance->page_maps, p);
   if (!page || (trace_page_type(page) == TRACE_PAGE_BAD)) {
-    GCPRINT(GCOUTF, "%s??? %p\n", prefix, p);
+    GCPRINT(GCOUTF, "%s%s %p %p\n", prefix, trace_source_kind(*_kind), p);
     return NULL;
   }
   p = trace_pointer_start(page, p);
@@ -80,7 +81,7 @@ static void *print_out_pointer(const char *prefix, void *p,
 	    p);
   }
 
-  return trace_backpointer(page, p);
+  return trace_backpointer(page, p, _kind);
 }
 
 static void print_traced_objects(int path_length_limit,
@@ -98,8 +99,9 @@ static void print_traced_objects(int path_length_limit,
   for (i = 0; i < found_object_count; i++) {
     void *p;
     int limit = path_length_limit;
+    int kind = 0;
     p = found_objects[i];
-    p = print_out_pointer("==* ", p, get_type_name, print_tagged_value);
+    p = print_out_pointer("==* ", p, get_type_name, print_tagged_value, &kind);
 
     j = 0; counter = 0; each = 1;
     while (p && limit) {
@@ -121,7 +123,7 @@ static void print_traced_objects(int path_length_limit,
             counter = 0;
           }
         }
-        p = print_out_pointer(" <- ", p, get_type_name, print_tagged_value);
+        p = print_out_pointer(" <- ", p, get_type_name, print_tagged_value, &kind);
         limit--;
       }
     }
diff --git a/src/racket/gc2/newgc.c b/src/racket/gc2/newgc.c
index f2778db83c..b4abf7009d 100644
--- a/src/racket/gc2/newgc.c
+++ b/src/racket/gc2/newgc.c
@@ -1939,13 +1939,14 @@ static void copy_backtrace_source(mpage *to_page, void *to_ptr,
   to_page->backtrace[to_delta+1] = from_page->backtrace[from_delta+1];
 }
 
-static void *get_backtrace(mpage *page, void *ptr)
+static void *get_backtrace(mpage *page, void *ptr, int *kind)
 /* ptr is after objhead */
 {
   uintptr_t delta;
 
   if (!page->backtrace) {
     /* This shouldn't happen, but fail more gracefully if it does. */
+    *kind = -1;
     return NULL;
   }
 
@@ -1957,6 +1958,8 @@ static void *get_backtrace(mpage *page, void *ptr)
   }
 
   delta = PPTR(ptr) - PPTR(page->addr);
+  *kind = ((intptr_t *)page->backtrace)[delta];
+
   return page->backtrace[delta - 1];
 }
 
@@ -3406,6 +3409,17 @@ static void *trace_pointer_start(mpage *page, void *p) {
 # define TRACE_PAGE_BAD PAGE_TYPES
 # define trace_page_is_big(page) (page)->size_class
 # define trace_backpointer get_backtrace
+const char *trace_source_kind(int kind)
+{
+  switch (kind) {
+  case BT_STACK: return "STACK";
+  case BT_ROOT: return "ROOT";
+  case BT_FINALIZER: return "FINALIZER";
+  case BT_WEAKLINK: return "WEAK-LINK";
+  case BT_IMMOBILE: return "IMMOBILE";
+  default: return "???";
+  }
+}
 # include "backtrace.c"
 #else
 # define reset_object_traces() /* */
@@ -4773,8 +4787,9 @@ static GC_print_tagged_value_proc stack_print_tagged_value;
 
 static void dump_stack_pos(void *a) 
 {
+  int kind = 0;
   GCPRINT(GCOUTF, " @%p: ", a);
-  print_out_pointer("", *(void **)a, stack_get_type_name, stack_print_tagged_value);
+  print_out_pointer("", *(void **)a, stack_get_type_name, stack_print_tagged_value, &kind);
 }
 
 # define GC_X_variable_stack GC_do_dump_variable_stack