xbt_config: kill an unused feature: unregistering variables

[simgrid.git] / include / xbt / string.hpp

diff --git a/include/xbt/string.hpp b/include/xbt/string.hpp
index 30d6737..9840855 100644 (file)
--- a/include/xbt/string.hpp
+++ b/include/xbt/string.hpp
@@ -4,10 +4,12 @@
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
-#ifndef SIMGRIC_XBT_STRING_HPP
-#define SIMGRIC_XBT_STRING_HPP
+#ifndef SIMGRID_XBT_STRING_HPP
+#define SIMGRID_XBT_STRING_HPP
 
-#ifdef HAVE_MC
+#include <simgrid_config.h>
+
+#if HAVE_MC
 
 #include <stdexcept>
 #include <cstddef>
@@ -30,10 +32,21 @@ struct string_data {
 
 /** A std::string with well-known representation
  *
- *  This is a (incomplete) drop-in replacement for std::string.
+ *  This is a (incomplete) drop-in replacement for `std::string`.
+ *  It has a fixed POD representation (`simgrid::xbt::string_data`)
+ *  which can be used to easily read the string content from another
+ *  process.
+ *
+ *  The internal representation of a `std::string` is private.
+ *  We could add some code to read this for a given implementation.
+ *  However, even if we focus on GNU libstdc++ with Itanium ABI
+ *  GNU libstdc++ currently has two different ABIs
  *
- *  This is used for cross-process access to strings
- *  (when the MC is enabled).
+ *  * the pre-C++11 is a pointer to a ref-counted
+ *    string-representation (with support for COW);
+ *
+ *  * the [C++11-conforming implementation](https://gcc.gnu.org/gcc-5/changes.html)
+ *    does not use refcouting/COW but has a small string optimization.
  */
 XBT_PUBLIC_CLASS string : private string_data {
   static const char NUL;
@@ -285,4 +298,4 @@ typedef std::string string;
 
 #endif
 
-#endif
\ No newline at end of file
+#endif