Re: [Boost-bugs] [Boost C++ Libraries] #12340: Combining boost::context and SEH doesn't work

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #12340: Combining boost::context and SEH doesn't work
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-08-02 18:00:59

#12340: Combining boost::context and SEH doesn't work
-------------------------------+---------------------
  Reporter:  nicolasbertolo@…  |      Owner:  olli
      Type:  Bugs              |     Status:  closed
 Milestone:  To Be Determined  |  Component:  context
   Version:  Boost 1.61.0      |   Severity:  Problem
Resolution:  worksforme        |   Keywords:
-------------------------------+---------------------

Comment (by anonymous):

 Mmmmh, that's good to know.

 It seems to contradict what this example shows:

 https://msdn.microsoft.com/en-

 us/library/windows/desktop/aa366803(v=vs.85).aspx

 >This sample does not show how to use the guard page fault to
 >"grow" a dynamic array, such as a stack.

 It implies that it is possible to enlarge a stack after a guard page
 fault.

 https://blogs.msdn.microsoft.com/oldnewthing/20060927-07/?p=29563/


 Explains that normal stack growth is implemented using guard pages, so it
 must be legal to extend a stack.

 Also note that the test does not enlarge the stack at all. It simply
 should detect the page fault and leave the function.

 There is something in boost::context that prevents the SEH code from
 catching access violations to the bottom of the stack.

 I made discovery: if at the bottom of the stack there are '''at least 3
 guard pages''' Windows will automatically extend the stack without ever
 letting the exception reach the exception handler, but when it runs out of
 guard pages it will throw a STATUS_STACK_OVERFLOW exception. If at the
 bottom of the stack there is a page marked PAGE_NOACCESS or if there are
 fewer than 3 guard pages a STATUS_ACCESS_VIOLATION exception will be
 thrown which won't pass through the exception filter (this is what IMHO is
 a bug).


 I changed the parameters of the VirtualProtect call in
 protected_fixedsize_stack.hpp

 {{{
 VirtualProtect(vp, traits_type::page_size() '''* 3''', PAGE_READWRITE |
 PAGE_GUARD /*PAGE_NOACCESS*/, & old_options);
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12340#comment:9>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.