[boost] Re: Warnings in Boost.Thread

From: Michael Glassford (glassfordm_at_[hidden])
Date: 2005-03-29 16:57:51

Janusz Piwowarski wrote:
> Hi all,
> 
> When Boost.Thread is compiled in release mode, there are a lot of 
> warnings about unused variable 'int loop_count' in read_write_mutex.cpp. 
> They comes from code like:
> 
> int loop_count = 0;
> while (m_state == -1)
> {
>    BOOST_ASSERT(++loop_count == 1);
>    ++m_num_waiting_readers;
>    m_waiting_readers.wait(l);
>    --m_num_waiting_readers;
> }
> 
> If loop is for second evaluation of condition only, i think it would be 
> better to write:
> 
> if (m_state == -1)
> {
>    ++m_num_waiting_readers;
>    m_waiting_readers.wait(l);
>    --m_num_waiting_readers;
>    BOOST_ASSERT(m_state != -1);
> }
> 

The warnings are now fixed, though not in the manner suggested. The loop 
is necessary, and there are times when it is correct to loop more than 
once. The loop count is debugging code to find times when the loop was 
executing more than once incorrectly. It is now completely removed from 
release builds.

Mike