[Boost-bugs] [Boost C++ Libraries] #4803: [function][patch] use a static "empty" target

Subject: [Boost-bugs] [Boost C++ Libraries] #4803: [function][patch] use a static "empty" target
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-10-29 19:38:22

#4803: [function][patch] use a static "empty" target
------------------------------+---------------------------------------------
 Reporter:  djwalker          |       Owner:  dgregor     
     Type:  Feature Requests  |      Status:  new         
Milestone:  To Be Determined  |   Component:  function    
  Version:  Boost 1.44.0      |    Severity:  Optimization
 Keywords:                    |  
------------------------------+---------------------------------------------
 boost::function throws bad_function_call if invoked when empty. Currently,
 this is implemented by performing a pointer comparison at runtime.
 Alternatively, boost::function's empty state could be represented by a
 static vtable object targeting an "empty" function which throws
 bad_function_call when invoked. There has been a lot of interest in this
 alternative scheme, which would trade the time overhead of a pointer
 comparison for an increase in space overhead in the initialized static
 variable section of the executable's data segment. The degree to which
 this trade-off will improve performance depends on compiler optimization.
 The attached patch implements a configuration macro,
 BOOST_FUNCTION_USE_STATIC_EMPTY, which allows the user to make this trade-
 off. The patch includes updated documentation and tests. I verified that
 the updated test suite passes on gcc 4.2, 4.5 and msvc 7.1, 10.

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Ticket URL: <https://svn.boost.org/trac/boost/ticket/4803>
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