externals: Update boost to 1.72 and add Boost Context

boost/context/continuation_ucontext.hpp

@@ -0,0 +1,526 @@
+
+//          Copyright Oliver Kowalke 2017.
+// 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_CONTINUATION_H
+#define BOOST_CONTEXT_CONTINUATION_H
+
+#include <boost/predef.h>
+#if BOOST_OS_MACOS
+#define _XOPEN_SOURCE 600
+#endif
+
+extern "C" {
+#include <ucontext.h>
+}
+
+#include <boost/context/detail/config.hpp>
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <functional>
+#include <memory>
+#include <ostream>
+#include <system_error>
+#include <tuple>
+#include <utility>
+
+#include <boost/assert.hpp>
+#include <boost/config.hpp>
+
+#include <boost/context/detail/disable_overload.hpp>
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+#include <boost/context/detail/exchange.hpp>
+#endif
+#include <boost/context/detail/externc.hpp>
+#if defined(BOOST_NO_CXX17_STD_INVOKE)
+#include <boost/context/detail/invoke.hpp>
+#endif
+#include <boost/context/fixedsize_stack.hpp>
+#include <boost/context/flags.hpp>
+#include <boost/context/preallocated.hpp>
+#if defined(BOOST_USE_SEGMENTED_STACKS)
+#include <boost/context/segmented_stack.hpp>
+#endif
+#include <boost/context/stack_context.hpp>
+
+#ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_PREFIX
+#endif
+
+namespace boost {
+namespace context {
+namespace detail {
+
+// tampoline function
+// entered if the execution context
+// is resumed for the first time
+template< typename Record >
+static void entry_func( void * data) noexcept {
+    Record * record = static_cast< Record * >( data);
+    BOOST_ASSERT( nullptr != record);
+    // start execution of toplevel context-function
+    record->run();
+}
+
+struct BOOST_CONTEXT_DECL activation_record {
+    ucontext_t                                                  uctx{};
+    stack_context                                               sctx{};
+    bool                                                        main_ctx{ true };
+	activation_record                                       *	from{ nullptr };
+    std::function< activation_record*(activation_record*&) >    ontop{};
+    bool                                                        terminated{ false };
+    bool                                                        force_unwind{ false };
+#if defined(BOOST_USE_ASAN)
+    void                                                    *   fake_stack{ nullptr };
+    void                                                    *   stack_bottom{ nullptr };
+    std::size_t                                                 stack_size{ 0 };
+#endif
+
+    static activation_record *& current() noexcept;
+
+    // used for toplevel-context
+    // (e.g. main context, thread-entry context)
+    activation_record() {
+        if ( BOOST_UNLIKELY( 0 != ::getcontext( & uctx) ) ) {
+            throw std::system_error(
+                    std::error_code( errno, std::system_category() ),
+                    "getcontext() failed");
+        }
+    }
+
+    activation_record( stack_context sctx_) noexcept :
+        sctx( sctx_ ),
+        main_ctx( false ) {
+    } 
+
+    virtual ~activation_record() {
+	}
+
+    activation_record( activation_record const&) = delete;
+    activation_record & operator=( activation_record const&) = delete;
+
+    bool is_main_context() const noexcept {
+        return main_ctx;
+    }
+
+    activation_record * resume() {
+		from = current();
+        // store `this` in static, thread local pointer
+        // `this` will become the active (running) context
+        current() = this;
+#if defined(BOOST_USE_SEGMENTED_STACKS)
+        // adjust segmented stack properties
+        __splitstack_getcontext( from->sctx.segments_ctx);
+        __splitstack_setcontext( sctx.segments_ctx);
+#endif
+#if defined(BOOST_USE_ASAN)
+        if ( terminated) {
+            __sanitizer_start_switch_fiber( nullptr, stack_bottom, stack_size);
+        } else {
+            __sanitizer_start_switch_fiber( & from->fake_stack, stack_bottom, stack_size);
+        }
+#endif
+        // context switch from parent context to `this`-context
+        ::swapcontext( & from->uctx, & uctx);
+#if defined(BOOST_USE_ASAN)
+        __sanitizer_finish_switch_fiber( current()->fake_stack,
+                                         (const void **) & current()->from->stack_bottom,
+                                         & current()->from->stack_size);
+#endif
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+        return exchange( current()->from, nullptr);
+#else
+        return std::exchange( current()->from, nullptr);
+#endif
+    }
+
+    template< typename Ctx, typename Fn >
+    activation_record * resume_with( Fn && fn) {
+		from = current();
+        // store `this` in static, thread local pointer
+        // `this` will become the active (running) context
+        // returned by continuation::current()
+        current() = this;
+#if defined(BOOST_NO_CXX14_GENERIC_LAMBDAS)
+        current()->ontop = std::bind(
+                [](typename std::decay< Fn >::type & fn, activation_record *& ptr){
+                    Ctx c{ ptr };
+                    c = fn( std::move( c) );
+                    if ( ! c) {
+                        ptr = nullptr;
+                    }
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+                    return exchange( c.ptr_, nullptr);
+#else
+                    return std::exchange( c.ptr_, nullptr);
+#endif
+                },
+                std::forward< Fn >( fn),
+                std::placeholders::_1);
+#else
+        current()->ontop = [fn=std::forward<Fn>(fn)](activation_record *& ptr){
+            Ctx c{ ptr };
+            c = fn( std::move( c) );
+            if ( ! c) {
+                ptr = nullptr;
+            }
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+            return exchange( c.ptr_, nullptr);
+#else
+            return std::exchange( c.ptr_, nullptr);
+#endif
+        };
+#endif
+#if defined(BOOST_USE_SEGMENTED_STACKS)
+        // adjust segmented stack properties
+        __splitstack_getcontext( from->sctx.segments_ctx);
+        __splitstack_setcontext( sctx.segments_ctx);
+#endif
+#if defined(BOOST_USE_ASAN)
+        __sanitizer_start_switch_fiber( & from->fake_stack, stack_bottom, stack_size);
+#endif
+        // context switch from parent context to `this`-context
+        ::swapcontext( & from->uctx, & uctx);
+#if defined(BOOST_USE_ASAN)
+        __sanitizer_finish_switch_fiber( current()->fake_stack,
+                                         (const void **) & current()->from->stack_bottom,
+                                         & current()->from->stack_size);
+#endif
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+        return exchange( current()->from, nullptr);
+#else
+        return std::exchange( current()->from, nullptr);
+#endif
+    }
+
+    virtual void deallocate() noexcept {
+    }
+};
+
+struct BOOST_CONTEXT_DECL activation_record_initializer {
+    activation_record_initializer() noexcept;
+    ~activation_record_initializer();
+};
+
+struct forced_unwind {
+    activation_record   *   from{ nullptr };
+#ifndef BOOST_ASSERT_IS_VOID
+    bool                    caught{ false };
+#endif
+
+    forced_unwind( activation_record * from_) noexcept :
+        from{ from_ } {
+    }
+
+#ifndef BOOST_ASSERT_IS_VOID
+    ~forced_unwind() {
+        BOOST_ASSERT( caught);
+    }
+#endif
+};
+
+template< typename Ctx, typename StackAlloc, typename Fn >
+class capture_record : public activation_record {
+private:
+    typename std::decay< StackAlloc >::type             salloc_;
+    typename std::decay< Fn >::type                     fn_;
+
+    static void destroy( capture_record * p) noexcept {
+        typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
+        stack_context sctx = p->sctx;
+        // deallocate activation record
+        p->~capture_record();
+        // destroy stack with stack allocator
+        salloc.deallocate( sctx);
+    }
+
+public:
+    capture_record( stack_context sctx, StackAlloc && salloc, Fn && fn) noexcept :
+        activation_record{ sctx },
+        salloc_{ std::forward< StackAlloc >( salloc) },
+        fn_( std::forward< Fn >( fn) ) {
+    }
+
+    void deallocate() noexcept override final {
+        BOOST_ASSERT( main_ctx || ( ! main_ctx && terminated) );
+        destroy( this);
+    }
+
+    void run() {
+#if defined(BOOST_USE_ASAN)
+        __sanitizer_finish_switch_fiber( fake_stack,
+                                         (const void **) & from->stack_bottom,
+                                         & from->stack_size);
+#endif
+        Ctx c{ from };
+        try {
+            // invoke context-function
+#if defined(BOOST_NO_CXX17_STD_INVOKE)
+            c = boost::context::detail::invoke( fn_, std::move( c) );
+#else
+            c = std::invoke( fn_, std::move( c) );
+#endif  
+        } catch ( forced_unwind const& ex) {
+            c = Ctx{ ex.from };
+#ifndef BOOST_ASSERT_IS_VOID
+            const_cast< forced_unwind & >( ex).caught = true;
+#endif
+        }
+        // this context has finished its task
+		from = nullptr;
+        ontop = nullptr;
+        terminated = true;
+        force_unwind = false;
+        c.resume();
+        BOOST_ASSERT_MSG( false, "continuation already terminated");
+    }
+};
+
+template< typename Ctx, typename StackAlloc, typename Fn >
+static activation_record * create_context1( StackAlloc && salloc, Fn && fn) {
+    typedef capture_record< Ctx, StackAlloc, Fn >  capture_t;
+
+    auto sctx = salloc.allocate();
+    // reserve space for control structure
+    void * storage = reinterpret_cast< void * >(
+            ( reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sizeof( capture_t) ) )
+            & ~ static_cast< uintptr_t >( 0xff) );
+    // placment new for control structure on context stack
+    capture_t * record = new ( storage) capture_t{
+            sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
+    // stack bottom
+    void * stack_bottom = reinterpret_cast< void * >(
+            reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sctx.size) );
+    // create user-context
+    if ( BOOST_UNLIKELY( 0 != ::getcontext( & record->uctx) ) ) {
+        record->~capture_t();
+        salloc.deallocate( sctx);
+        throw std::system_error(
+                std::error_code( errno, std::system_category() ),
+                "getcontext() failed");
+    }
+    record->uctx.uc_stack.ss_sp = stack_bottom;
+    // 64byte gap between control structure and stack top
+    record->uctx.uc_stack.ss_size = reinterpret_cast< uintptr_t >( storage) -
+            reinterpret_cast< uintptr_t >( stack_bottom) - static_cast< uintptr_t >( 64);
+    record->uctx.uc_link = nullptr;
+    ::makecontext( & record->uctx, ( void (*)() ) & entry_func< capture_t >, 1, record);
+#if defined(BOOST_USE_ASAN)
+    record->stack_bottom = record->uctx.uc_stack.ss_sp;
+    record->stack_size = record->uctx.uc_stack.ss_size;
+#endif
+    return record;
+}
+
+template< typename Ctx, typename StackAlloc, typename Fn >
+static activation_record * create_context2( preallocated palloc, StackAlloc && salloc, Fn && fn) {
+    typedef capture_record< Ctx, StackAlloc, Fn >  capture_t; 
+
+    // reserve space for control structure
+    void * storage = reinterpret_cast< void * >(
+            ( reinterpret_cast< uintptr_t >( palloc.sp) - static_cast< uintptr_t >( sizeof( capture_t) ) )
+            & ~ static_cast< uintptr_t >( 0xff) );
+    // placment new for control structure on context stack
+    capture_t * record = new ( storage) capture_t{
+            palloc.sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
+    // stack bottom
+    void * stack_bottom = reinterpret_cast< void * >(
+            reinterpret_cast< uintptr_t >( palloc.sctx.sp) - static_cast< uintptr_t >( palloc.sctx.size) );
+    // create user-context
+    if ( BOOST_UNLIKELY( 0 != ::getcontext( & record->uctx) ) ) {
+        record->~capture_t();
+        salloc.deallocate( palloc.sctx);
+        throw std::system_error(
+                std::error_code( errno, std::system_category() ),
+                "getcontext() failed");
+    }
+    record->uctx.uc_stack.ss_sp = stack_bottom;
+    // 64byte gap between control structure and stack top
+    record->uctx.uc_stack.ss_size = reinterpret_cast< uintptr_t >( storage) -
+            reinterpret_cast< uintptr_t >( stack_bottom) - static_cast< uintptr_t >( 64);
+    record->uctx.uc_link = nullptr;
+    ::makecontext( & record->uctx,  ( void (*)() ) & entry_func< capture_t >, 1, record);
+#if defined(BOOST_USE_ASAN)
+    record->stack_bottom = record->uctx.uc_stack.ss_sp;
+    record->stack_size = record->uctx.uc_stack.ss_size;
+#endif
+    return record;
+}
+
+}
+
+class BOOST_CONTEXT_DECL continuation {
+private:
+    friend struct detail::activation_record;
+
+    template< typename Ctx, typename StackAlloc, typename Fn >
+    friend class detail::capture_record;
+
+	template< typename Ctx, typename StackAlloc, typename Fn >
+	friend detail::activation_record * detail::create_context1( StackAlloc &&, Fn &&);
+
+	template< typename Ctx, typename StackAlloc, typename Fn >
+	friend detail::activation_record * detail::create_context2( preallocated, StackAlloc &&, Fn &&);
+
+    template< typename StackAlloc, typename Fn >
+    friend continuation
+    callcc( std::allocator_arg_t, StackAlloc &&, Fn &&);
+
+    template< typename StackAlloc, typename Fn >
+    friend continuation
+    callcc( std::allocator_arg_t, preallocated, StackAlloc &&, Fn &&);
+
+    detail::activation_record   *   ptr_{ nullptr };
+
+    continuation( detail::activation_record * ptr) noexcept :
+        ptr_{ ptr } {
+    }
+
+public:
+    continuation() = default;
+
+    ~continuation() {
+        if ( BOOST_UNLIKELY( nullptr != ptr_) && ! ptr_->main_ctx) {
+            if ( BOOST_LIKELY( ! ptr_->terminated) ) {
+                ptr_->force_unwind = true;
+                ptr_->resume();
+                BOOST_ASSERT( ptr_->terminated);
+            }
+            ptr_->deallocate();
+        }
+    }
+
+    continuation( continuation const&) = delete;
+    continuation & operator=( continuation const&) = delete;
+
+    continuation( continuation && other) noexcept {
+        swap( other);
+    }
+
+    continuation & operator=( continuation && other) noexcept {
+        if ( BOOST_LIKELY( this != & other) ) {
+            continuation tmp = std::move( other);
+            swap( tmp);
+        }
+        return * this;
+    }
+
+    continuation resume() & {
+        return std::move( * this).resume();
+    }
+
+    continuation resume() && {
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+        detail::activation_record * ptr = detail::exchange( ptr_, nullptr)->resume();
+#else
+        detail::activation_record * ptr = std::exchange( ptr_, nullptr)->resume();
+#endif
+        if ( BOOST_UNLIKELY( detail::activation_record::current()->force_unwind) ) {
+            throw detail::forced_unwind{ ptr};
+        } else if ( BOOST_UNLIKELY( nullptr != detail::activation_record::current()->ontop) ) {
+            ptr = detail::activation_record::current()->ontop( ptr);
+            detail::activation_record::current()->ontop = nullptr;
+        }
+        return { ptr };
+    }
+
+    template< typename Fn >
+    continuation resume_with( Fn && fn) & {
+        return std::move( * this).resume_with( std::forward< Fn >( fn) );
+    }
+
+    template< typename Fn >
+    continuation resume_with( Fn && fn) && {
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+        detail::activation_record * ptr =
+            detail::exchange( ptr_, nullptr)->resume_with< continuation >( std::forward< Fn >( fn) );
+#else
+        detail::activation_record * ptr =
+            std::exchange( ptr_, nullptr)->resume_with< continuation >( std::forward< Fn >( fn) );
+#endif
+        if ( BOOST_UNLIKELY( detail::activation_record::current()->force_unwind) ) {
+            throw detail::forced_unwind{ ptr};
+        } else if ( BOOST_UNLIKELY( nullptr != detail::activation_record::current()->ontop) ) {
+            ptr = detail::activation_record::current()->ontop( ptr);
+            detail::activation_record::current()->ontop = nullptr;
+        }
+        return { ptr };
+    }
+
+    explicit operator bool() const noexcept {
+        return nullptr != ptr_ && ! ptr_->terminated;
+    }
+
+    bool operator!() const noexcept {
+        return nullptr == ptr_ || ptr_->terminated;
+    }
+
+    bool operator<( continuation const& other) const noexcept {
+        return ptr_ < other.ptr_;
+    }
+
+    template< typename charT, class traitsT >
+    friend std::basic_ostream< charT, traitsT > &
+    operator<<( std::basic_ostream< charT, traitsT > & os, continuation const& other) {
+        if ( nullptr != other.ptr_) {
+            return os << other.ptr_;
+        } else {
+            return os << "{not-a-context}";
+        }
+    }
+
+    void swap( continuation & other) noexcept {
+        std::swap( ptr_, other.ptr_);
+    }
+};
+
+template<
+    typename Fn,
+    typename = detail::disable_overload< continuation, Fn >
+>
+continuation
+callcc( Fn && fn) {
+	return callcc(
+			std::allocator_arg,
+#if defined(BOOST_USE_SEGMENTED_STACKS)
+			segmented_stack(),
+#else
+			fixedsize_stack(),
+#endif
+			std::forward< Fn >( fn) );
+}
+
+template< typename StackAlloc, typename Fn >
+continuation
+callcc( std::allocator_arg_t, StackAlloc && salloc, Fn && fn) {
+	return continuation{
+		detail::create_context1< continuation >(
+				std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) }.resume();
+}
+
+template< typename StackAlloc, typename Fn >
+continuation
+callcc( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn) {
+	return continuation{
+		detail::create_context2< continuation >(
+				palloc, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) }.resume();
+}
+
+inline
+void swap( continuation & l, continuation & r) noexcept {
+    l.swap( r);
+}
+
+}}
+
+#ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_SUFFIX
+#endif
+
+#endif // BOOST_CONTEXT_CONTINUATION_H