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rec: Add support for boost::context >= 1.61

(cherry picked from commit f53de85)
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1 parent fbf562c commit ddf6fa532945dc303abc187fe5f2e3a6417a61c5 @rgacogne rgacogne committed Sep 23, 2016
Showing with 77 additions and 6 deletions.
  1. +67 −2 pdns/mtasker_fcontext.cc
  2. +10 −4 pdns/recursordist/configure.ac
@@ -23,10 +23,15 @@
#include <exception>
#include <cassert>
#include <type_traits>
-#include <boost/context/fcontext.hpp>
#include <boost/version.hpp>
-
+#if BOOST_VERSION >= 106100
+#include <boost/context/detail/fcontext.hpp>
+using boost::context::detail::make_fcontext;
+#else
+#include <boost/context/fcontext.hpp>
using boost::context::make_fcontext;
+#endif /* BOOST_VERSION >= 106100 */
+
#if BOOST_VERSION < 105600
/* Note: This typedef means functions taking fcontext_t*, like jump_fcontext(),
@@ -57,8 +62,15 @@ jump_fcontext (fcontext_t* const ofc, fcontext_t const nfc,
}
}
#else
+
+#if BOOST_VERSION < 106100
using boost::context::fcontext_t;
using boost::context::jump_fcontext;
+#else
+using boost::context::detail::fcontext_t;
+using boost::context::detail::jump_fcontext;
+using boost::context::detail::transfer_t;
+#endif /* BOOST_VERSION < 106100 */
static_assert (std::is_pointer<fcontext_t>::value,
"Boost Context has changed the fcontext_t type again :-(");
@@ -68,15 +80,21 @@ static_assert (std::is_pointer<fcontext_t>::value,
* jump. args_t simply provides a way to pass more by reference.
*/
struct args_t {
+#if BOOST_VERSION < 106100
fcontext_t prev_ctx = nullptr;
+#endif
pdns_ucontext_t* self = nullptr;
boost::function<void(void)>* work = nullptr;
};
extern "C" {
static
void
+#if BOOST_VERSION < 106100
threadWrapper (intptr_t const xargs) {
+#else
+threadWrapper (transfer_t const t) {
+#endif
/* Access the args passed from pdns_makecontext, and copy them directly from
* the calling stack on to ours (we're now using the MThreads stack).
* This saves heap allocating an args object, at the cost of an extra
@@ -86,11 +104,28 @@ threadWrapper (intptr_t const xargs) {
* the behaviour of the System V implementation, which can inherently only
* be passed ints and pointers.
*/
+#if BOOST_VERSION < 106100
auto args = reinterpret_cast<args_t*>(xargs);
+#else
+ auto args = reinterpret_cast<args_t*>(t.data);
+#endif
auto ctx = args->self;
auto work = args->work;
+ /* we switch back to pdns_makecontext() */
+#if BOOST_VERSION < 106100
jump_fcontext (reinterpret_cast<fcontext_t*>(&ctx->uc_mcontext),
static_cast<fcontext_t>(args->prev_ctx), 0);
+#else
+ transfer_t res = jump_fcontext (t.fctx, 0);
+ /* we got switched back from pdns_swapcontext() */
+ if (res.data) {
+ /* if res.data is not a nullptr, it holds a pointer to the context
+ we just switched from, and we need to fill it to be able to
+ switch back to it later. */
+ fcontext_t* ptr = static_cast<fcontext_t*>(res.data);
+ *ptr = res.fctx;
+ }
+#endif
args = nullptr;
try {
@@ -102,9 +137,14 @@ threadWrapper (intptr_t const xargs) {
/* Emulate the System V uc_link feature. */
auto const next_ctx = ctx->uc_link->uc_mcontext;
+#if BOOST_VERSION < 106100
jump_fcontext (reinterpret_cast<fcontext_t*>(&ctx->uc_mcontext),
static_cast<fcontext_t>(next_ctx),
static_cast<bool>(ctx->exception));
+#else
+ jump_fcontext (static_cast<fcontext_t>(next_ctx), 0);
+#endif
+
#ifdef NDEBUG
__builtin_unreachable();
#endif
@@ -125,10 +165,27 @@ pdns_ucontext_t::~pdns_ucontext_t
void
pdns_swapcontext
(pdns_ucontext_t& __restrict octx, pdns_ucontext_t const& __restrict ctx) {
+ /* we either switch back to threadwrapper() if it's the first time,
+ or we switch back to pdns_swapcontext(),
+ in both case we will be returning from a call to jump_fcontext(). */
+#if BOOST_VERSION < 106100
if (jump_fcontext (reinterpret_cast<fcontext_t*>(&octx.uc_mcontext),
static_cast<fcontext_t>(ctx.uc_mcontext), 0)) {
std::rethrow_exception (ctx.exception);
}
+#else
+ transfer_t res = jump_fcontext (static_cast<fcontext_t>(ctx.uc_mcontext), &octx.uc_mcontext);
+ if (res.data) {
+ /* if res.data is not a nullptr, it holds a pointer to the context
+ we just switched from, and we need to fill it to be able to
+ switch back to it later. */
+ fcontext_t* ptr = static_cast<fcontext_t*>(res.data);
+ *ptr = res.fctx;
+ }
+ if (ctx.exception) {
+ std::rethrow_exception (ctx.exception);
+ }
+#endif
}
void
@@ -142,7 +199,15 @@ pdns_makecontext
args_t args;
args.self = &ctx;
args.work = &start;
+ /* jumping to threadwrapper */
+#if BOOST_VERSION < 106100
jump_fcontext (reinterpret_cast<fcontext_t*>(&args.prev_ctx),
static_cast<fcontext_t>(ctx.uc_mcontext),
reinterpret_cast<intptr_t>(&args));
+#else
+ transfer_t res = jump_fcontext (static_cast<fcontext_t>(ctx.uc_mcontext),
+ &args);
+ /* back from threadwrapper, updating the context */
+ ctx.uc_mcontext = res.fctx;
+#endif
}
@@ -46,7 +46,7 @@ pdns_context_library="System V ucontexts"
AC_DEFUN([PDNS_SELECT_CONTEXT_IMPL], [
AC_MSG_CHECKING([whether Boost is new enough to use the context library...])
- if test $boost_major_version -ge 152 -a $boost_major_version -lt 161 ; then
+ if test $boost_major_version -ge 152; then
AC_MSG_RESULT([yes])
if test $boost_major_version -ge 157; then
BOOST_THREAD([$1])
@@ -55,9 +55,15 @@ AC_DEFUN([PDNS_SELECT_CONTEXT_IMPL], [
LDFLAGS="$LDFLAGS $BOOST_THREAD_LDFLAGS"
fi
AC_MSG_NOTICE([checking whether the Boost context library actually links...])
- BOOST_FIND_HEADER([boost/context/fcontext.hpp], [ : ], [
- BOOST_FIND_LIB([context], [$1], [boost/context/fcontext.hpp], [[]])
- ])
+ if test $boost_major_version -ge 161; then
+ BOOST_FIND_HEADER([boost/context/detail/fcontext.hpp], [ : ], [
+ BOOST_FIND_LIB([context], [$1], [boost/context/detail/fcontext.hpp], [[]])
+ ])
+ else
+ BOOST_FIND_HEADER([boost/context/fcontext.hpp], [ : ], [
+ BOOST_FIND_LIB([context], [$1], [boost/context/fcontext.hpp], [[]])
+ ])
+ fi
case $boost_cv_lib_context in
(yes)
pdns_context_library="Boost context"

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