Re: [Boost-users] [coroutine] Bus error on Mac OS X 10.5

Subject: Re: [Boost-users] [coroutine] Bus error on Mac OS X 10.5
From: Nat Goodspeed (nat_at_[hidden])
Date: 2009-04-08 00:26:02

Nat Goodspeed wrote:

> the 'banana' example program built -- but I get a bus 
> error trying to run it.
> 
> I did find an exchange on the Apple mailing list [1] in which Kevin Van 
> Vechten recommends #defining _XOPEN_SOURCE before #include <ucontext.h>.
> 
> Unfortunately, adding such a #define does not resolve my bus error.

banana.cpp now runs on my Mac! For closure, here's what I found.

There were two crash issues. One is indeed fixed by #defining 
_XOPEN_SOURCE -- /if/ your #define precedes the first #include of 
sys/_structs.h! This was a little tricky to resolve, since many system 
headers end up pulling that in.

This only matters in boost/coroutine/detail/context_posix.hpp, so I kept 
the #define there -- but test whether the system file has already been 
#included. If so, you get an #error to the effect that you must #include 
coroutine headers before anything that #includes <ucontext.h>.

Then I had to move some internal #includes that were forcing that #error 
even when coroutine.hpp is first.

Moving boost/coroutine/detail/context_posix.hpp before most other 
#includes revealed that it uses BOOST_ASSERT without #including 
<boost/assert.hpp>. I've added that #include.

The other crash issue is that 8192 is way too small a default stack. On 
this platform, SIGSTKSZ is 131072, or 16x the hard-coded 
default_stack_size. I changed the definition of 
ucontext_context_impl::default_stack_size to SIGSTKSZ.

I changed boost/coroutine/detail/posix_utility.hpp to reference MAP_ANON 
rather than MAP_ANONYMOUS in the __APPLE__ case -- thanks Tom!

All these changes are in a patch file [2].

> [1] http://lists.apple.com/archives/darwin-dev/2008/Jan/msg00232.html
> [2] attached boost-coroutine.patch

diff -cr orig/boost-coroutine/boost/coroutine/coroutine.hpp ./boost/coroutine/coroutine.hpp
*** orig/boost-coroutine/boost/coroutine/coroutine.hpp	Sun Aug 20 13:11:16 2006
--- ./boost/coroutine/coroutine.hpp	Tue Apr  7 23:38:11 2009
***************
*** 28,33 ****
--- 28,35 ----
  
  #ifndef BOOST_COROUTINE_COROUTINE_HPP_20060512
  #define BOOST_COROUTINE_COROUTINE_HPP_20060512
+ // default_context_impl.hpp must be first for weird Apple bug
+ #include <boost/coroutine/detail/default_context_impl.hpp>
  #include <cstddef>
  #include <boost/preprocessor/repetition.hpp>
  #include <boost/tuple/tuple.hpp>
***************
*** 37,43 ****
  #include <boost/call_traits.hpp>
  #include <boost/coroutine/detail/arg_max.hpp>
  #include <boost/coroutine/detail/coroutine_impl.hpp>
- #include <boost/coroutine/detail/default_context_impl.hpp>
  #include <boost/coroutine/detail/is_callable.hpp>
  #include <boost/coroutine/detail/argument_packer.hpp>
  #include <boost/coroutine/detail/argument_unpacker.hpp>
--- 39,44 ----
diff -cr orig/boost-coroutine/boost/coroutine/detail/context_posix.hpp ./boost/coroutine/detail/context_posix.hpp
*** orig/boost-coroutine/boost/coroutine/detail/context_posix.hpp	Sun Aug 20 13:11:09 2006
--- ./boost/coroutine/detail/context_posix.hpp	Tue Apr  7 23:40:17 2009
***************
*** 28,39 ****
  
  #ifndef BOOST_COROUTINE_CONTEXT_POSIX_HPP_20060601
  #define BOOST_COROUTINE_CONTEXT_POSIX_HPP_20060601
  #include <boost/config.hpp>
  
  #if defined(_XOPEN_UNIX) && defined(_XOPEN_VERSION) && _XOPEN_VERSION >= 500
  
  /*
!  * makecontex based context implementation. Should be available on all
   * SuSv2 compliant UNIX systems. 
   * NOTE: this implementation is not
   * optimal as the makecontext API saves and restore the signal mask.
--- 28,55 ----
  
  #ifndef BOOST_COROUTINE_CONTEXT_POSIX_HPP_20060601
  #define BOOST_COROUTINE_CONTEXT_POSIX_HPP_20060601
+ 
+ // NOTE (per http://lists.apple.com/archives/darwin-dev/2008/Jan/msg00232.html):
+ // > Why the bus error? What am I doing wrong? 
+ // This is a known issue where getcontext(3) is writing past the end of the
+ // ucontext_t struct when _XOPEN_SOURCE is not defined (rdar://problem/5578699 ).
+ // As a workaround, define _XOPEN_SOURCE before including ucontext.h.
+ #if defined(__APPLE__) && ! defined(_XOPEN_SOURCE)
+ #define _XOPEN_SOURCE
+ // However, the above #define will only affect <ucontext.h> if it has not yet
+ // been #included by something else!
+ #if defined(_STRUCT_UCONTEXT)
+ #error You must #include coroutine headers before anything that #includes <ucontext.h>
+ #endif
+ #endif
+ 
  #include <boost/config.hpp>
+ #include <boost/assert.hpp>
  
  #if defined(_XOPEN_UNIX) && defined(_XOPEN_VERSION) && _XOPEN_VERSION >= 500
  
  /*
!  * makecontext based context implementation. Should be available on all
   * SuSv2 compliant UNIX systems. 
   * NOTE: this implementation is not
   * optimal as the makecontext API saves and restore the signal mask.
***************
*** 43,48 ****
--- 59,65 ----
   * it is unlikely that they will be removed any time soon.
   */
  #include <ucontext.h>
+ #include <signal.h>                 // SIGSTKSZ
  #include <boost/noncopyable.hpp>
  #include <boost/coroutine/exception.hpp>
  #include <boost/coroutine/detail/posix_utility.hpp>
***************
*** 83,89 ****
      public:
        typedef ucontext_context_impl_base context_impl_base;
  
!       enum {default_stack_size = 8192};
  
      
        /**
--- 100,106 ----
      public:
        typedef ucontext_context_impl_base context_impl_base;
  
!       enum {default_stack_size = SIGSTKSZ};
  
      
        /**
diff -cr orig/boost-coroutine/boost/coroutine/detail/posix_utility.hpp ./boost/coroutine/detail/posix_utility.hpp
*** orig/boost-coroutine/boost/coroutine/detail/posix_utility.hpp	Sun Aug 20 13:11:09 2006
--- ./boost/coroutine/detail/posix_utility.hpp	Wed Apr  1 09:57:03 2009
***************
*** 129,135 ****
--- 129,139 ----
      void * stack = ::mmap(NULL,
                            size,
                            PROT_EXEC|PROT_READ|PROT_WRITE,
+ #if defined(__APPLE__)
+ 			  MAP_PRIVATE|MAP_ANON,
+ #else // ! __APPLE__
                            MAP_PRIVATE|MAP_ANONYMOUS,
+ #endif // ! __APPLE__
                            -1,
                            0
                            );
diff -cr orig/boost-coroutine/boost/coroutine/future.hpp ./boost/coroutine/future.hpp
*** orig/boost-coroutine/boost/coroutine/future.hpp	Sun Aug 20 13:11:16 2006
--- ./boost/coroutine/future.hpp	Tue Apr  7 23:38:42 2009
***************
*** 33,38 ****
--- 33,40 ----
  #ifndef BOOST_COROUTINE_WAIT_MAX
  #define BOOST_COROUTINE_WAIT_MAX 10
  #endif
+ // default_context_impl.hpp must be first for weird Apple bug
+ #include <boost/coroutine/detail/default_context_impl.hpp>
  #include <boost/none.hpp>
  #include <boost/config.hpp>
  #include <boost/tuple/tuple.hpp>
***************
*** 48,54 ****
  #include <boost/coroutine/detail/call_impl.hpp>
  #include <boost/coroutine/detail/wait_impl.hpp>
  #include <boost/coroutine/detail/future_impl.hpp>
- #include <boost/coroutine/detail/default_context_impl.hpp>
  
  namespace boost { namespace coroutines {
  
--- 50,55 ----
diff -cr orig/boost-coroutine/libs/coroutine/example/banana.cpp ./libs/coroutine/example/banana.cpp
*** orig/boost-coroutine/libs/coroutine/example/banana.cpp	Sun Aug 20 13:12:02 2006
--- ./libs/coroutine/example/banana.cpp	Tue Apr  7 23:40:46 2009
***************
*** 26,35 ****
  //  (See accompanying file LICENSE_1_0.txt or copy at
  //  http://www.boost.org/LICENSE_1_0.txt)
  
  #include <iostream>
  #include <string>
  #include <boost/bind.hpp>
- #include <boost/coroutine/coroutine.hpp>
  
  namespace coroutines = boost::coroutines;
  using coroutines::coroutine;
--- 26,35 ----
  //  (See accompanying file LICENSE_1_0.txt or copy at
  //  http://www.boost.org/LICENSE_1_0.txt)
  
+ #include <boost/coroutine/coroutine.hpp>
  #include <iostream>
  #include <string>
  #include <boost/bind.hpp>
  
  namespace coroutines = boost::coroutines;
  using coroutines::coroutine;