Re: debug container mutex association

[Jonathan Wakely <jwakely@redhat.com>]

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On 20/09/16 09:53 +0100, Jonathan Wakely wrote:
>On 19/09/16 21:56 +0200, François Dumont wrote:
>>Hi
>>
>>   Following our conversation here is a much simpler patch. I just 
>>consider that all debug containers will have the same alignment.
>>
>>   Even if I submit this patch as a whole I will commit into pieces, 
>>at least one for the pure cleanup parts and one for the debug.cc 
>>change.
>>
>>   Among those changes there is:
>>-       __gnu_cxx::__scoped_lock(this->_M_get_mutex());
>>+       __gnu_cxx::__scoped_lock __l(this->_M_get_mutex());
>>
>>   I would appreciate if you could tell me what was happening with 
>>the initial expression. I don't understand why it is compiling. I 
>>even tried the same in debug.cc and started having compilation 
>>errors.
>
>It creates a temporary __scoped_lock, which immediately goes out of
>scope and unlocks the mutex again. This should be fixed on the gcc-5
>and gcc-6 branches too.

I'm committing this to the gcc-5 and gcc-6 branches.



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commit 5218b515fdb54881d8a2b87c28eb5fd84c52db01
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Sep 27 16:22:28 2016 +0100

    Fix lifetime of mutex lock in debug iterator
    
    	* include/debug/safe_iterator.h (_Safe_iterator::operator++()): Fix
    	lifetime of lock.

diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index 5368f3b..3f5a7f8 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -296,7 +296,7 @@ namespace __gnu_debug
 	_GLIBCXX_DEBUG_VERIFY(this->_M_incrementable(),
 			      _M_message(__msg_bad_inc)
 			      ._M_iterator(*this, "this"));
-	__gnu_cxx::__scoped_lock(this->_M_get_mutex());
+	__gnu_cxx::__scoped_lock __l(this->_M_get_mutex());
 	++base();
 	return *this;
       }