Drop support for boost below 1.61

Summary: [Folly] Drop support for boost below 1.61, which means removing multiple versions of support for `boost-context` embedded in `folly/fibers/`.

Reviewed By: fredemmott

Differential Revision: D22779795

fbshipit-source-id: fafc9b38784dcb206283e11d01d77dd8655354a6

folly/fibers/BoostContextCompatibility.h

@@ -16,23 +16,12 @@
 
 #pragma once
 
-#include <boost/version.hpp>
-#if BOOST_VERSION >= 106100
 #include <boost/context/detail/fcontext.hpp>
-#else
-#include <boost/context/fcontext.hpp>
-#endif
 #include <glog/logging.h>
 
 /**
  * Wrappers for different versions of boost::context library
  * API reference for different versions
- * Boost 1.51:
- * http://www.boost.org/doc/libs/1_51_0/libs/context/doc/html/context/context/boost_fcontext.html
- * Boost 1.52:
- * http://www.boost.org/doc/libs/1_52_0/libs/context/doc/html/context/context/boost_fcontext.html
- * Boost 1.56:
- * http://www.boost.org/doc/libs/1_56_0/libs/context/doc/html/context/context/boost_fcontext.html
  * Boost 1.61:
  * https://github.com/boostorg/context/blob/boost-1.61.0/include/boost/context/detail/fcontext.hpp
  */
@@ -43,25 +32,9 @@ namespace folly {
 namespace fibers {
 
 class FiberImpl {
-#if BOOST_VERSION >= 106100
   using FiberContext = boost::context::detail::fcontext_t;
-#elif BOOST_VERSION >= 105600
-  using FiberContext = boost::context::fcontext_t;
-#elif BOOST_VERSION >= 105200
-  using FiberContext = boost::context::fcontext_t*;
-#else
-  using FiberContext = boost::ctx::fcontext_t;
-#endif
 
-#if BOOST_VERSION >= 106100
   using MainContext = boost::context::detail::fcontext_t;
-#elif BOOST_VERSION >= 105600
-  using MainContext = boost::context::fcontext_t;
-#elif BOOST_VERSION >= 105200
-  using MainContext = boost::context::fcontext_t;
-#else
-  using MainContext = boost::ctx::fcontext_t;
-#endif
 
  public:
   FiberImpl(
@@ -70,56 +43,28 @@ class FiberImpl {
       size_t stackSize)
       : func_(std::move(func)) {
     auto stackBase = stackLimit + stackSize;
-#if BOOST_VERSION >= 106100
     stackBase_ = stackBase;
     fiberContext_ =
         boost::context::detail::make_fcontext(stackBase, stackSize, &fiberFunc);
-#elif BOOST_VERSION >= 105200
-    fiberContext_ =
-        boost::context::make_fcontext(stackBase, stackSize, &fiberFunc);
-#else
-    fiberContext_.fc_stack.limit = stackLimit;
-    fiberContext_.fc_stack.base = stackBase;
-    make_fcontext(&fiberContext_, &fiberFunc);
-#endif
   }
 
   void activate() {
-#if BOOST_VERSION >= 106100
     auto transfer = boost::context::detail::jump_fcontext(fiberContext_, this);
     fiberContext_ = transfer.fctx;
     auto context = reinterpret_cast<intptr_t>(transfer.data);
-#elif BOOST_VERSION >= 105200
-    auto context = boost::context::jump_fcontext(
-        &mainContext_, fiberContext_, reinterpret_cast<intptr_t>(this));
-#else
-    auto context = jump_fcontext(
-        &mainContext_, &fiberContext_, reinterpret_cast<intptr_t>(this));
-#endif
     DCHECK_EQ(0, context);
   }
 
   void deactivate() {
-#if BOOST_VERSION >= 106100
     auto transfer =
         boost::context::detail::jump_fcontext(mainContext_, nullptr);
     mainContext_ = transfer.fctx;
     fixStackUnwinding();
     auto context = reinterpret_cast<intptr_t>(transfer.data);
-#elif BOOST_VERSION >= 105600
-    auto context =
-        boost::context::jump_fcontext(&fiberContext_, mainContext_, 0);
-#elif BOOST_VERSION >= 105200
-    auto context =
-        boost::context::jump_fcontext(fiberContext_, &mainContext_, 0);
-#else
-    auto context = jump_fcontext(&fiberContext_, &mainContext_, 0);
-#endif
     DCHECK_EQ(this, reinterpret_cast<FiberImpl*>(context));
   }
 
  private:
-#if BOOST_VERSION >= 106100
   static void fiberFunc(boost::context::detail::transfer_t transfer) {
     auto fiberImpl = reinterpret_cast<FiberImpl*>(transfer.data);
     fiberImpl->mainContext_ = transfer.fctx;
@@ -139,13 +84,6 @@ class FiberImpl {
   }
 
   unsigned char* stackBase_;
-#else
-  static void fiberFunc(intptr_t arg) {
-    auto fiberImpl = reinterpret_cast<FiberImpl*>(arg);
-    fiberImpl->func_();
-  }
-#endif
-
   folly::Function<void()> func_;
   FiberContext fiberContext_;
   MainContext mainContext_;