From 2d8c6ed5f35ea2ed5f5d706ff100e1563e990b25 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Mon, 13 Jul 2015 21:46:21 -0400
Subject: [PATCH] Added basic call history reporting

---
 TODO      | 13 -------------
 runtime.c |  8 +++++---
 test2.scm |  8 ++++++--
 3 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/TODO b/TODO
index 9c9aaae5..5de28edb 100644
--- a/TODO
+++ b/TODO
@@ -13,19 +13,6 @@ Working TODO list:
  - self-hosting, there are a lot of accumulated TODO's that need to be addressed
 
    - improved error handling:
-     (1) - code traces
-       could pass filename and define name (if applicable) to c-compile-exp,
-       and record it for each lambda. could then add code to each lambda to 
-       write that info to a circular buffer when the function is called.
-       that would enable a primitive stack trace to be maintained at runtime.
-
-       ideally use an array of (char *) and a pointer incremented like (i = (i + 1) % size)
-       to treat it as a circular buffer
-
-       as a starting point, could encode lambda name and filename and get the
-       circular buffer and runtime reporting working. then come back and add
-       Scheme function names.
-
      - type checking
        ideally want to do this in a way that minimized performance impacts.
        will probaby require extensive checks within apply() though, since that
diff --git a/runtime.c b/runtime.c
index 0bd1e6b7..d162c7bb 100644
--- a/runtime.c
+++ b/runtime.c
@@ -80,9 +80,11 @@ void Cyc_st_init() {
 }
 
 void Cyc_st_add(char *frame) { 
-  // TODO: do not add if (idx - 1) == frame, since that causes recursion to remove older frames
-  Cyc_Stack_Traces[Cyc_Stack_Trace_Idx] = frame;
-  Cyc_Stack_Trace_Idx = (Cyc_Stack_Trace_Idx + 1) % MAX_STACK_TRACES;
+  // Do not allow recursion to remove older frames
+  if (frame != Cyc_Stack_Traces[(Cyc_Stack_Trace_Idx - 1) % MAX_STACK_TRACES]) {
+    Cyc_Stack_Traces[Cyc_Stack_Trace_Idx] = frame;
+    Cyc_Stack_Trace_Idx = (Cyc_Stack_Trace_Idx + 1) % MAX_STACK_TRACES;
+  }
 }
 
 void Cyc_st_print(FILE *out) {
diff --git a/test2.scm b/test2.scm
index 8b35f804..183dfb6f 100644
--- a/test2.scm
+++ b/test2.scm
@@ -2,10 +2,14 @@
         (scheme file)
         (scheme write))
 
+(map
+  (lambda (_)
 (set! x 1)
-(write x)
-(write 'Cyc_procedure)
+;(write x)
+;(write 'Cyc_procedure)
 (open-input-file "1.scm")
+)
+(list 1))
 ;;; TODO: C macros for funcall1, etc are not being generated even though entries are set
 ;;;    in the vector. must be another problem inspecting the vector ???
 ;(write 'hello)