UrlFile::sweep shouldn't free smart allocated objs

UrlFile::sweep shouldn't free smart allocated objs

Closes #1643

Reviewed By: @jdelong

Differential Revision: D1144563

Pulled By: @scannell

hphp/runtime/base/string-buffer.h

@@ -37,6 +37,9 @@ public:
 
 /*
  * Efficient string concatenation.
+ *
+ * StringBuffer is designed not to contain any malloc()d memory (only
+ * per-request smart allocated memory) based on sweeping-related assumptions.
  */
 struct StringBuffer {
   static const int kDefaultOutputLimit = StringData::MaxSize;

hphp/runtime/base/url-file.cpp

@@ -23,7 +23,6 @@
 
 namespace HPHP {
 
-IMPLEMENT_OBJECT_ALLOCATION(UrlFile)
 ///////////////////////////////////////////////////////////////////////////////
 
 const StaticString s_http_response_header("http_response_header");
@@ -43,6 +42,12 @@ UrlFile::UrlFile(const char *method /* = "GET" */,
   m_isLocal = false;
 }
 
+void UrlFile::sweep() {
+  using std::string;
+  m_error.~string();
+  MemFile::sweep();
+}
+
 const StaticString
   s_remove_user_pass_pattern("#://[^@]+@#"),
   s_remove_user_pass_replace("://");