Re: [Boost-bugs] [Boost C++ Libraries] #10850: gcc-x86-implementation of "atomic_exchange_and_add" triggers intel's "unitialized variable" runtime check

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #10850: gcc-x86-implementation of "atomic_exchange_and_add" triggers intel's "unitialized variable" runtime check
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-12-04 18:23:51

#10850: gcc-x86-implementation of "atomic_exchange_and_add" triggers intel's
"unitialized variable" runtime check
--------------------------------------+-----------------------
  Reporter:  fabian.hachenberg@…      |      Owner:  pdimov
      Type:  Patches                  |     Status:  new
 Milestone:  To Be Determined         |  Component:  smart_ptr
   Version:  Boost Development Trunk  |   Severity:  Problem
Resolution:                           |   Keywords:
--------------------------------------+-----------------------

Comment (by fabian.hachenberg@…):

 Sorry for the messup of code blocks.

 Here's the original code
 {{{
 inline int atomic_exchange_and_add( int * pw, int dv )
 {
     // int r = *pw;
     // *pw += dv;
     // return r;

     int r;

     __asm__ __volatile__
     (
         "lock\n\t"
         "xadd %1, %0":
         "=m"( *pw ), "=r"( r ): // outputs (%0, %1)
         "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1)
         "memory", "cc" // clobbers
     );

     return r;
 }
 }}}

 Here's the patches version
 {{{
 inline int atomic_exchange_and_add( int * pw, int dv )
 {
     // int r = *pw;
     // *pw += dv;
     // return r;

     __asm__ __volatile__
     (
         "lock\n\t"
         "xadd %1, %0":
         "+m"( *pw ), "+r"( dv ): // input/output (%0, %1)
                 :
         "memory", "cc" // clobbers
     );

     return dv;
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/10850#comment:1>
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