From 7812c604f4a63b92572a0789d17b3f10829acf7b Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 9 Dec 2016 06:21:41 -0700
Subject: [PATCH] fix native stack traversal for stack dumps

When caching the result of a stack traversal, adjust
the actual stack only after the traversal is complete
to avoid interfering with libunwind's decoding of the
stack.
---
 racket/src/racket/src/jitcall.c  |  5 +++--
 racket/src/racket/src/jitstack.c | 24 ++++++++++++++++--------
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/racket/src/racket/src/jitcall.c b/racket/src/racket/src/jitcall.c
index c8b6413d26..d42387edba 100644
--- a/racket/src/racket/src/jitcall.c
+++ b/racket/src/racket/src/jitcall.c
@@ -1461,7 +1461,8 @@ typedef struct {
 static void jit_register_sub_func(mz_jit_state *jitter, void *code, Scheme_Object *protocol, int gcable)
 /* protocol: #f => normal lightweight call protocol
              void => next return address is in LOCAL2
-             eof => name to use is in LOCAL2 */
+             eof => name to use is in LOCAL2
+             null => no name, but usual frame */
 {
   void *code_end;
 
@@ -1482,7 +1483,7 @@ void scheme_jit_register_helper_func(mz_jit_state *jitter, void *code, int gcabl
 {
 #if defined(MZ_USE_DWARF_LIBUNWIND) || defined(_WIN64)
   /* Null indicates that there's no function name to report, but the
-     stack should be unwound manually using the JJIT-generated convention. */
+     stack should be unwound manually using the JIT-generated convention. */
   jit_register_sub_func(jitter, code, scheme_null, gcable);
 #endif  
 }
diff --git a/racket/src/racket/src/jitstack.c b/racket/src/racket/src/jitstack.c
index 1ab8297151..6a3aa5b4a2 100644
--- a/racket/src/racket/src/jitstack.c
+++ b/racket/src/racket/src/jitstack.c
@@ -161,9 +161,9 @@ static void set_cache(void *p, Scheme_Object *last)
 
 Scheme_Object *scheme_native_stack_trace(void)
 {
-  void *p, *q, *cache_frame_p;
+  void *p, *q, *cache_frame_p, *set_cache_sp = NULL;
   uintptr_t stack_end, real_stack_end, stack_start, halfway;
-  Scheme_Object *name, *last = NULL, *first = NULL, *tail;
+  Scheme_Object *name, *last = NULL, *first = NULL, *tail, *set_cache_last = NULL;
   int cache_had_name = 0;
 #ifdef MZ_USE_DWARF_LIBUNWIND
   unw_context_t cx;
@@ -200,7 +200,7 @@ Scheme_Object *scheme_native_stack_trace(void)
 #ifdef MZ_USE_DWARF_LIBUNWIND
   unw_getcontext(&cx);
   unw_init_local(&c, &cx);
-  unw_set_safe_pointer_range(&c, stack_start, stack_end);
+  unw_set_safe_pointer_range(&c, stack_start, real_stack_end);
   use_unw = 1;
   p = NULL;
 #else
@@ -296,7 +296,8 @@ Scheme_Object *scheme_native_stack_trace(void)
 
       if (cache_sp) {
 	if (STK_COMP((uintptr_t)halfway, (uintptr_t)cache_sp)) {
-	  set_cache(cache_sp, last);
+          set_cache_sp = cache_sp;
+          set_cache_last = last;
 	  if (!name)
 	    shift_cache_to_next = 1;
 	  halfway = stack_end;
@@ -313,7 +314,10 @@ Scheme_Object *scheme_native_stack_trace(void)
     }
 
     if (shift_cache_to_next)
-      stack_cache_stack[stack_cache_stack_pos].cache = tail;
+      set_cache_last = tail;
+
+    if (set_cache_sp)
+      set_cache(set_cache_sp, set_cache_last);
 
     if (last)
       SCHEME_CDR(last) = tail;
@@ -438,7 +442,7 @@ Scheme_Object *scheme_native_stack_trace(void)
 	first = name;
       last = name;
       if (shift_cache_to_next) {
-        stack_cache_stack[stack_cache_stack_pos].cache = last;
+        set_cache_last = last;
         shift_cache_to_next = 0;
       }
       added_list_elem = 1;
@@ -458,7 +462,8 @@ Scheme_Object *scheme_native_stack_trace(void)
        it will use the return address from the stack. */
     if (STK_COMP((uintptr_t)halfway, (uintptr_t)cache_frame_p)
 	&& cache_had_name) {
-      set_cache(cache_frame_p, last);
+      set_cache_sp = cache_frame_p;
+      set_cache_last = last;
       if (!added_list_elem)
 	shift_cache_to_next = 1;
       halfway = stack_end;
@@ -509,7 +514,10 @@ Scheme_Object *scheme_native_stack_trace(void)
   }
 
   if (shift_cache_to_next)
-    stack_cache_stack[stack_cache_stack_pos].cache = tail;
+    set_cache_last = tail;
+
+  if (set_cache_sp)
+    set_cache(set_cache_sp, set_cache_last);
 
 #ifdef MZ_USE_DWARF_LIBUNWIND
   unw_destroy_local(&c);