Re: Fw: [Boost-users] Problem with shared_ptr and pthreads_mutex_lock

[Paolo Carlini <pcarlini at suse dot de>]

Paolo Carlini wrote:

> Kurt Kohler wrote:
>
>> I should emphasize that this isn't just a problem with what valgrind
>> reports.
>
> In fact, I'm seeing something fishy in the usage of _M_mutex (i.e.,
> its initialization) in our code for shared_ptr. I will try to tell you
> more as soon as possible.

Indeed, the mutex is not initialized at all. The below is a possible,
minimal, fix (for sure we are a long way from a well tested and
optimized implementation). Can you test it (*) with your application??

Thanks,
Paolo.

(*) Just in case: given the structure of the library, rebuilding
compiler and library is not necessary, simply patching the concerned
header file in its installation place will do.

///////////////

--- boost_shared_ptr.h.~1.3.~	2005-08-17 04:14:08.000000000 +0200
+++ boost_shared_ptr.h	2005-10-06 23:34:12.000000000 +0200
@@ -54,6 +54,11 @@
 #ifndef _BOOST_SHARED_PTR_H
 #define _BOOST_SHARED_PTR_H 1
 
+namespace __gnu_internal
+{
+  static __glibcxx_mutex_define_initialized(_M_counted_base_mutex);
+}
+
 // namespace std::tr1
 namespace std
 {
@@ -131,7 +136,7 @@
   void
   add_ref_lock()
   {
-    __gnu_cxx::lock lock(_M_mutex);
+    __gnu_cxx::lock lock(__gnu_internal::_M_counted_base_mutex);
     if (__gnu_cxx::__exchange_and_add(&_M_use_count, 1) == 0)
     {
       _M_use_count = 0;
@@ -145,8 +150,8 @@
     if (__gnu_cxx::__exchange_and_add(&_M_use_count, -1) == 1)
     {
       dispose();
-      __glibcxx_mutex_lock(_M_mutex);
-      __glibcxx_mutex_unlock(_M_mutex);
+      __glibcxx_mutex_lock(__gnu_internal::_M_counted_base_mutex);
+      __glibcxx_mutex_unlock(__gnu_internal::_M_counted_base_mutex);
       weak_release();
     }
   }
@@ -162,8 +167,8 @@
   {
     if (__gnu_cxx::__exchange_and_add(&_M_weak_count, -1) == 1)
     {
-      __glibcxx_mutex_lock(_M_mutex);
-      __glibcxx_mutex_unlock(_M_mutex);
+      __glibcxx_mutex_lock(__gnu_internal::_M_counted_base_mutex);
+      __glibcxx_mutex_unlock(__gnu_internal::_M_counted_base_mutex);
       destroy();
     }
   }
@@ -181,7 +186,6 @@
 
   _Atomic_word _M_use_count;        // #shared
   _Atomic_word _M_weak_count;       // #weak + (#shared != 0)
-  __gnu_cxx::mutex_type _M_mutex;
 };
 
 template <typename _Ptr, typename _Deleter>