Add an API to set aside and restore cx->fp. bug 377090, r=brendan

js/src/jsapi.c

@@ -4421,6 +4421,34 @@ JS_SetCallReturnValue2(JSContext *cx, jsval v)
 #endif
 }
 
+JS_PUBLIC_API(JSStackFrame *)
+JS_SaveFrameChain(JSContext *cx)
+{
+    JSStackFrame *fp;
+
+    fp = cx->fp;
+    if (!fp)
+        return fp;
+
+    JS_ASSERT(!fp->dormantNext);
+    fp->dormantNext = cx->dormantFrameChain;
+    cx->dormantFrameChain = fp;
+    cx->fp = NULL;
+    return fp;
+}
+
+JS_PUBLIC_API(void)
+JS_RestoreFrameChain(JSContext *cx, JSStackFrame *fp)
+{
+    JS_ASSERT(!cx->fp);
+    if (!fp)
+        return;
+
+    cx->fp = fp;
+    cx->dormantFrameChain = fp->dormantNext;
+    fp->dormantNext = NULL;
+}
+
 /************************************************************************/
 
 JS_PUBLIC_API(JSString *)

js/src/jsapi.h

@@ -1848,6 +1848,25 @@ JS_IsAssigning(JSContext *cx);
 extern JS_PUBLIC_API(void)
 JS_SetCallReturnValue2(JSContext *cx, jsval v);
 
+/*
+ * Saving and restoring frame chains.
+ *
+ * These two functions are used to set aside cx->fp while that frame is
+ * inactive. After a call to JS_SaveFrameChain, it looks as if there is no
+ * code running on cx. Before calling JS_RestoreFrameChain, cx's call stack
+ * must be balanced and all nested calls to JS_SaveFrameChain must have had
+ * matching JS_RestoreFrameChain calls.
+ *
+ * JS_SaveFrameChain deals with cx not having any code running on it. A null
+ * return does not signify an error and JS_RestoreFrameChain handles null
+ * frames.
+ */
+extern JS_PUBLIC_API(JSStackFrame *)
+JS_SaveFrameChain(JSContext *cx);
+
+extern JS_PUBLIC_API(void)
+JS_RestoreFrameChain(JSContext *cx, JSStackFrame *fp);
+
 /************************************************************************/
 
 /*

js/src/jsprvtd.h

@@ -116,7 +116,6 @@ typedef struct JSRegExpStatics      JSRegExpStatics;
 typedef struct JSScope              JSScope;
 typedef struct JSScopeOps           JSScopeOps;
 typedef struct JSScopeProperty      JSScopeProperty;
-typedef struct JSStackFrame         JSStackFrame;
 typedef struct JSStackHeader        JSStackHeader;
 typedef struct JSStringBuffer       JSStringBuffer;
 typedef struct JSSubString          JSSubString;

js/src/jspubtd.h

@@ -140,6 +140,7 @@ typedef struct JSXMLObjectOps    JSXMLObjectOps;
 typedef struct JSRuntime         JSRuntime;
 typedef struct JSRuntime         JSTaskState;   /* XXX deprecated name */
 typedef struct JSScript          JSScript;
+typedef struct JSStackFrame      JSStackFrame;
 typedef struct JSString          JSString;
 typedef struct JSXDRState        JSXDRState;
 typedef struct JSExceptionState  JSExceptionState;