Recover trapped opcode in js_GetIndexFromBytecode (416665, r=igor).

js/src/jsdbgapi.c

@@ -161,21 +161,16 @@ JS_SetTrap(JSContext *cx, JSScript *script, jsbytecode *pc,
 JS_PUBLIC_API(JSOp)
 JS_GetTrapOpcode(JSContext *cx, JSScript *script, jsbytecode *pc)
 {
+    JSRuntime *rt;
     JSTrap *trap;
+    JSOp op;
 
-    DBG_LOCK_EVAL(cx->runtime, trap = FindTrap(cx->runtime, script, pc));
-    if (!trap) {
-#ifdef JS_THREADSAFE
-        /*
-         * If we lost a race with another thread, return JSOP_LIMIT so our
-         * caller can detect this case and do something sane.
-         */
-#else
-        JS_ASSERT(0);   /* XXX can't happen */
-#endif
-        return JSOP_LIMIT;
-    }
-    return trap->op;
+    rt = cx->runtime;
+    DBG_LOCK(rt);
+    trap = FindTrap(rt, script, pc);
+    op = trap ? trap->op : (JSOp) *pc;
+    DBG_UNLOCK(rt);
+    return op;
 }
 
 static void

js/src/jsopcode.c

@@ -123,12 +123,15 @@ GetJumpOffset(jsbytecode *pc, jsbytecode *pc2)
 }
 
 uintN
-js_GetIndexFromBytecode(JSScript *script, jsbytecode *pc, ptrdiff_t pcoff)
+js_GetIndexFromBytecode(JSContext *cx, JSScript *script, jsbytecode *pc,
+                        ptrdiff_t pcoff)
 {
     JSOp op;
     uintN span, base;
 
     op = (JSOp)*pc;
+    if (op == JSOP_TRAP)
+        op = JS_GetTrapOpcode(cx, script, pc);
     JS_ASSERT(js_CodeSpec[op].length >= 1 + pcoff + UINT16_LEN);
 
     /*
@@ -241,8 +244,6 @@ js_Disassemble1(JSContext *cx, JSScript *script, jsbytecode *pc,
       case JOF_BYTE:
         if (op == JSOP_TRAP) {
             op = JS_GetTrapOpcode(cx, script, pc);
-            if (op == JSOP_LIMIT)
-                return 0;
             len = (ptrdiff_t) js_CodeSpec[op].length;
         }
         break;
@@ -256,7 +257,7 @@ js_Disassemble1(JSContext *cx, JSScript *script, jsbytecode *pc,
       case JOF_ATOM:
       case JOF_OBJECT:
       case JOF_REGEXP:
-        index = js_GetIndexFromBytecode(script, pc, 0);
+        index = js_GetIndexFromBytecode(cx, script, pc, 0);
         if (type == JOF_ATOM) {
             JS_GET_SCRIPT_ATOM(script, index, atom);
             v = ATOM_KEY(atom);
@@ -348,7 +349,7 @@ js_Disassemble1(JSContext *cx, JSScript *script, jsbytecode *pc,
       case JOF_SLOTATOM:
       case JOF_SLOTOBJECT:
         fprintf(fp, " %u", GET_VARNO(pc));
-        index = js_GetIndexFromBytecode(script, pc, VARNO_LEN);
+        index = js_GetIndexFromBytecode(cx, script, pc, VARNO_LEN);
         if (type == JOF_SLOTATOM) {
             JS_GET_SCRIPT_ATOM(script, index, atom);
             v = ATOM_KEY(atom);
@@ -4131,10 +4132,7 @@ Decompile(SprintStack *ss, jsbytecode *pc, intN nb, JSOp nextop)
 #endif /* JS_HAS_EXPORT_IMPORT */
 
               case JSOP_TRAP:
-                op = JS_GetTrapOpcode(cx, jp->script, pc);
-                if (op == JSOP_LIMIT)
-                    return NULL;
-                saveop = op;
+                saveop = op = JS_GetTrapOpcode(cx, jp->script, pc);
                 *pc = op;
                 cs = &js_CodeSpec[op];
                 len = cs->length;

js/src/jsopcode.h

@@ -302,10 +302,14 @@ js_puts(JSPrinter *jp, const char *s);
 
 /*
  * Get index operand from the bytecode using a bytecode analysis to deduce the
- * the index register.
+ * the index register. This function is infallible, in spite of taking cx as
+ * its first parameter; it uses only cx->runtime when calling JS_GetTrapOpcode.
+ * The GET_*_FROM_BYTECODE macros that call it pick up cx from their caller's
+ * lexical environments.
  */
 uintN
-js_GetIndexFromBytecode(JSScript *script, jsbytecode *pc, ptrdiff_t pcoff);
+js_GetIndexFromBytecode(JSContext *cx, JSScript *script, jsbytecode *pc,
+                        ptrdiff_t pcoff);
 
 /*
  * A slower version of GET_ATOM when the caller does not want to maintain
@@ -313,13 +317,13 @@ js_GetIndexFromBytecode(JSScript *script, jsbytecode *pc, ptrdiff_t pcoff);
  */
 #define GET_ATOM_FROM_BYTECODE(script, pc, pcoff, atom)                       \
     JS_BEGIN_MACRO                                                            \
-        uintN index_ = js_GetIndexFromBytecode((script), (pc), (pcoff));      \
+        uintN index_ = js_GetIndexFromBytecode(cx, (script), (pc), (pcoff));  \
         JS_GET_SCRIPT_ATOM((script), index_, atom);                           \
     JS_END_MACRO
 
 #define GET_OBJECT_FROM_BYTECODE(script, pc, pcoff, obj)                      \
     JS_BEGIN_MACRO                                                            \
-        uintN index_ = js_GetIndexFromBytecode((script), (pc), (pcoff));      \
+        uintN index_ = js_GetIndexFromBytecode(cx, (script), (pc), (pcoff));  \
         JS_GET_SCRIPT_OBJECT((script), index_, obj);                          \
     JS_END_MACRO
 
@@ -331,7 +335,7 @@ js_GetIndexFromBytecode(JSScript *script, jsbytecode *pc, ptrdiff_t pcoff);
 
 #define GET_REGEXP_FROM_BYTECODE(script, pc, pcoff, obj)                      \
     JS_BEGIN_MACRO                                                            \
-        uintN index_ = js_GetIndexFromBytecode((script), (pc), (pcoff));      \
+        uintN index_ = js_GetIndexFromBytecode(cx, (script), (pc), (pcoff));  \
         JS_GET_SCRIPT_REGEXP((script), index_, obj);                          \
     JS_END_MACRO