externals: Update boost to 1.72 and add Boost Context

boost/context/posix/segmented_stack.hpp

@@ -0,0 +1,82 @@
+
+//          Copyright Oliver Kowalke 2014.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_CONTEXT_SEGMENTED_H
+#define BOOST_CONTEXT_SEGMENTED_H
+
+#include <cstddef>
+#include <new>
+
+#include <boost/config.hpp>
+
+#include <boost/context/detail/config.hpp>
+#include <boost/context/stack_context.hpp>
+#include <boost/context/stack_traits.hpp>
+
+#ifdef BOOST_HAS_ABI_HEADERS
+#  include BOOST_ABI_PREFIX
+#endif
+
+// forward declaration for splitstack-functions defined in libgcc
+extern "C" {
+void *__splitstack_makecontext( std::size_t,
+                                void * [BOOST_CONTEXT_SEGMENTS],
+                                std::size_t *);
+
+void __splitstack_releasecontext( void * [BOOST_CONTEXT_SEGMENTS]);
+
+void __splitstack_resetcontext( void * [BOOST_CONTEXT_SEGMENTS]);
+
+void __splitstack_block_signals_context( void * [BOOST_CONTEXT_SEGMENTS],
+                                         int * new_value, int * old_value);
+}
+
+namespace boost {
+namespace context {
+
+template< typename traitsT >
+class basic_segmented_stack {
+private:
+    std::size_t     size_;
+
+public:
+    typedef traitsT traits_type;
+
+    basic_segmented_stack( std::size_t size = traits_type::default_size() ) BOOST_NOEXCEPT_OR_NOTHROW :
+        size_( size) {
+    }
+
+    stack_context allocate() {
+        stack_context sctx;
+        void * vp = __splitstack_makecontext( size_, sctx.segments_ctx, & sctx.size);
+        if ( ! vp) throw std::bad_alloc();
+
+        // sctx.size is already filled by __splitstack_makecontext
+        sctx.sp = static_cast< char * >( vp) + sctx.size;
+
+        int off = 0;
+        __splitstack_block_signals_context( sctx.segments_ctx, & off, 0);
+
+        return sctx;
+    }
+
+    void deallocate( stack_context & sctx) BOOST_NOEXCEPT_OR_NOTHROW {
+        __splitstack_releasecontext( sctx.segments_ctx);
+    }
+};
+
+typedef basic_segmented_stack< stack_traits > segmented_stack;
+# if defined(BOOST_USE_SEGMENTED_STACKS)
+typedef segmented_stack default_stack;
+# endif
+
+}}
+
+#ifdef BOOST_HAS_ABI_HEADERS
+#  include BOOST_ABI_SUFFIX
+#endif
+
+#endif // BOOST_CONTEXT_SEGMENTED_H