[Boost-bugs] [Boost C++ Libraries] #1929: Borland/Codegear C++ 2007 creating boost::thread fails at initialisation of membervar boost::thread::thread_info

Subject: [Boost-bugs] [Boost C++ Libraries] #1929: Borland/Codegear C++ 2007 creating boost::thread fails at initialisation of membervar boost::thread::thread_info
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-05-18 15:40:10

#1929: Borland/Codegear C++ 2007 creating boost::thread fails at initialisation of
membervar boost::thread::thread_info
-----------------------------------------------+----------------------------
 Reporter:  Giel van Schijndel <me_at_mortis.eu>  |        Type:  Bugs        
   Status:  new                                |   Milestone:  Boost 1.36.0
Component:  None                               |     Version:  Boost 1.35.0
 Severity:  Problem                            |    Keywords:              
-----------------------------------------------+----------------------------
 I'm attempting to create a thread in Borland/Codegear C++ 2007 (win32) by
 means of code similar to this:
 {{{
 #!cpp
 class Threaded
 {
     volatile bool _quit;
     boost::thread _thread;

     public:
         Threaded() :
             _quit(false),
             _thread(boost::ref(*this))
         {}

         void operator()()
         {
             while (!_quit)
                 /* do stuff here */;
         }
 };
 }}}

 The results of several debugging sessions:

 However as soon as the constructor of boost::thread gets invoked it will
 call boost::thread::make_thread. This allocates some heap memory using the
 Windows API and uses an in-place new to construct a detail::thread_data<T>
 in that memory. The allocation and construction seem to work out very
 well.

 As soon as boost::thread::make_thread_info returns however it seems to
 fail to assign the pointer to member variable thread_info in the
 constructor.

 I tried the below patch for debugging purposes, to see what happens.
 Somehow the new variable (`tinfo`) remains NULL (all heap memory is
 initialised to zero while debugging, hence the NULL) however. Thus it
 seems that this compiler (borland) somehow fails to generate code that
 properly assigns the pointer to boost::thread's member variables.

 However, somehow assigning the value of `tinfo` to an on-stack variable
 ''does'' yield the correct pointer, while at the time the debugger says
 that `tinfo` is still NULL, even though assigning it to another pointer
 yields a non-NULL (and correct) value. So maybe it's pointer value is kept
 in a register but only gets assigned to stack based variables but not to
 member variables?

 What's even more strange is that compiling a minimal test case ''outside''
 of the IDE (using bjam) produces code that works. Unfortunately I cannot
 use bjam for my project as it depends on Borland's VCL GUI library (if
 it's possible to use bjam with Borland's VCL anyway please tell me where
 to look/what to do, as up till now I've only failed miserably and have
 little experience with bjam anyway).

 Thus this ^^ leads me to believe that something differs in the compiler
 options, I haven't got the slightest clue what it could be though. I've
 got all optimisations turned off. Although I have no clue how to know what
 command line options the IDE is calling the compiler with, so I cannot
 compare it.

 {{{
 #!diff
 Index: boost/thread/win32/thread.hpp
 ===================================================================
 --- boost/thread/win32/thread.hpp       (revision 45484)
 +++ boost/thread/win32/thread.hpp       (working copy)
 @@ -196,6 +196,7 @@
          };

          mutable boost::mutex thread_info_mutex;
 +        detail::thread_data_base* tinfo;
          detail::thread_data_ptr thread_info;

          static unsigned __stdcall thread_start_function(void* param);
 @@ -214,7 +215,7 @@
          }
  #else
          template<typename F>
 -        static inline detail::thread_data_ptr make_thread_info(F f)
 +        static inline detail::thread_data_base* make_thread_info(F f)
          {
              return detail::heap_new<thread_data<F> >(f);
          }
 @@ -238,7 +239,8 @@
  #else
          template <class F>
          explicit thread(F f):
 -            thread_info(make_thread_info(f))
 +            tinfo(make_thread_info(f)),
 +            thread_info(tinfo)
          {
              start_thread();
          }
 }}}

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/1929>
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