Bug 487684 - Store the last trace PC to pass into the decompiler. r=igor

js/src/jscntxt.cpp

@@ -1607,7 +1607,7 @@ js_ReportValueErrorFlags(JSContext *cx, uintN flags, const uintN errorNumber,
 
 #if defined DEBUG && defined XP_UNIX
 /* For gdb usage. */
-void js_traceon(JSContext *cx)  { cx->tracefp = stderr; cx->tracePrevOp = JSOP_LIMIT; }
+void js_traceon(JSContext *cx)  { cx->tracefp = stderr; cx->tracePrevPc = NULL; }
 void js_traceoff(JSContext *cx) { cx->tracefp = NULL; }
 #endif
 

js/src/jscntxt.h

@@ -932,7 +932,7 @@ struct JSContext {
     char                *lastMessage;
 #ifdef DEBUG
     void                *tracefp;
-    JSOp                tracePrevOp;
+    jsbytecode          *tracePrevPc;
 #endif
 
     /* Per-context optional error reporter. */

js/src/jsinterp.cpp

@@ -2104,9 +2104,10 @@ js_TraceOpcode(JSContext *cx)
      * Operations in prologues don't produce interesting values, and
      * js_DecompileValueGenerator isn't set up to handle them anyway.
      */
-    if (cx->tracePrevOp != JSOP_LIMIT && regs->pc >= fp->script->main) {
-        ndefs = js_GetStackDefs(cx, &js_CodeSpec[cx->tracePrevOp],
-                                cx->tracePrevOp, fp->script, regs->pc);
+    if (cx->tracePrevPc && regs->pc >= fp->script->main) {
+        JSOp tracePrevOp = JSOp(*cx->tracePrevPc);
+        ndefs = js_GetStackDefs(cx, &js_CodeSpec[tracePrevOp], tracePrevOp,
+                                fp->script, cx->tracePrevPc);
 
         /*
          * If there aren't that many elements on the stack, then 
@@ -2159,7 +2160,7 @@ js_TraceOpcode(JSContext *cx)
         }
         fprintf(tracefp, " @ %u\n", (uintN) (regs->sp - StackBase(fp)));
     }
-    cx->tracePrevOp = op;
+    cx->tracePrevPc = regs->pc;
 
     /* It's nice to have complete traces when debugging a crash.  */
     fflush(tracefp);
@@ -7288,6 +7289,10 @@ js_Interpret(JSContext *cx)
     ok &= js_UnwindScope(cx, fp, 0, ok || cx->throwing);
     JS_ASSERT(regs.sp == StackBase(fp));
 
+#ifdef DEBUG
+    cx->tracePrevPc = NULL;
+#endif
+
     if (inlineCallCount)
         goto inline_return;
 

js/src/shell/js.cpp

@@ -1882,7 +1882,7 @@ Tracing(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
     if (cx->tracefp && cx->tracefp != stderr)
       fclose((FILE *)cx->tracefp);
     cx->tracefp = file;
-    cx->tracePrevOp = JSOP_LIMIT;
+    cx->tracePrevPc = NULL;
     return JS_TRUE;
 
  bad_argument: