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authorBoris Kolpackov <boris@codesynthesis.com>2016-12-13 16:39:58 +0200
committerBoris Kolpackov <boris@codesynthesis.com>2016-12-13 16:39:58 +0200
commita4199b808fd678f74935d540490eae9dc78a9ffe (patch)
tree16d1f0e583c926838b92722e000fae2c1ac4aa9e /butl
parentb05e24a7f512c1f005dbcb67b3fce8b3d16e110e (diff)
Fix thread safety issue
Diffstat (limited to 'butl')
-rw-r--r--butl/config47
-rw-r--r--butl/diagnostics40
-rw-r--r--butl/diagnostics.cxx17
-rw-r--r--butl/utility46
-rw-r--r--butl/utility.cxx7
5 files changed, 123 insertions, 34 deletions
diff --git a/butl/config b/butl/config
new file mode 100644
index 0000000..71ebd23
--- /dev/null
+++ b/butl/config
@@ -0,0 +1,47 @@
+// file : butl/config -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_CONFIG
+#define BUTL_CONFIG
+
+#include <cstddef> // _LIBCPP_VERSION, __GLIBCXX__
+
+// thread_local
+//
+// If this macro is undefined then we assume one can use __thread but only
+// for values that do not require dynamic (runtime) initialization.
+//
+// Apparently Apple's Clang "temporarily disabled" C++11 thread_local
+// until they can implement a "fast" version, which reportedly happened in
+// XCode 8. So for now we will continue using __thread for this target.
+//
+#ifdef __apple_build_version__
+# if __apple_build_version__ >= 8000000
+# define BUTL_CXX11_THREAD_LOCAL
+# endif
+#else
+# define BUTL_CXX11_THREAD_LOCAL
+#endif
+
+// std::uncaught_exceptions()
+//
+// VC has it since 1900 which is the lowest version we support.
+//
+#if defined(_MSC_VER)
+# define BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+//
+// Clang's libc++ seems to have it for a while so we assume it's there (it
+// doesn't define a feature test macros).
+//
+#elif defined(_LIBCPP_VERSION)
+# define BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+//
+// GCC libstdc++ has it since GCC 6 and it defines the feature test macro.
+// We will also use this for any other runtime.
+//
+#elif defined(__cpp_lib_uncaught_exceptions)
+# define BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+#endif
+
+#endif // BUTL_CONFIG
diff --git a/butl/diagnostics b/butl/diagnostics
index b56ef10..b76e384 100644
--- a/butl/diagnostics
+++ b/butl/diagnostics
@@ -9,7 +9,7 @@
#include <ostream>
#include <sstream>
#include <utility> // move(), forward()
-#include <exception> // uncaught_exception()
+#include <exception> // uncaught_exception(s)()
#include <butl/export>
#include <butl/utility>
@@ -36,17 +36,21 @@ namespace butl
return r;
}
- diag_record (): empty_ (true), epilogue_ (nullptr) {}
+ diag_record ()
+ :
+#ifdef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+ uncaught_ (std::uncaught_exceptions ()),
+#endif
+ empty_ (true),
+ epilogue_ (nullptr) {}
template <typename B>
explicit
- diag_record (const diag_prologue<B>& p)
- : empty_ (true), epilogue_ (nullptr) { *this << p;}
+ diag_record (const diag_prologue<B>& p): diag_record () { *this << p;}
template <typename B>
explicit
- diag_record (const diag_mark<B>& m)
- : empty_ (true), epilogue_ (nullptr) { *this << m;}
+ diag_record (const diag_mark<B>& m): diag_record () { *this << m;}
~diag_record () noexcept (false);
@@ -85,19 +89,16 @@ namespace butl
diag_record (diag_record&&);
#else
diag_record (diag_record&& r)
-#ifndef __GLIBCXX__
- : os (std::move (r.os))
+ :
+#ifdef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+ uncaught_ (r.uncaught_),
#endif
+ empty_ (r.empty_),
+ epilogue_ (r.epilogue_),
+ os (std::move (r.os))
{
- empty_ = r.empty_;
- epilogue_ = r.epilogue_;
-
if (!empty_)
{
-#ifdef __GLIBCXX__
- // os << r.os.str ();
- assert (false); // No way to copy extra stream data?
-#endif
r.empty_ = true;
r.epilogue_ = nullptr;
}
@@ -109,12 +110,15 @@ namespace butl
diag_record (const diag_record&) = delete;
diag_record& operator= (const diag_record&) = delete;
- public:
- mutable std::ostringstream os;
-
protected:
+#ifdef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+ const int uncaught_;
+#endif
mutable bool empty_;
mutable diag_epilogue* epilogue_;
+
+ public:
+ mutable std::ostringstream os;
};
template <typename B>
diff --git a/butl/diagnostics.cxx b/butl/diagnostics.cxx
index e4c22dc..ad84810 100644
--- a/butl/diagnostics.cxx
+++ b/butl/diagnostics.cxx
@@ -28,14 +28,19 @@ namespace butl
diag_record::
~diag_record () noexcept (false)
{
- // Don't flush the record if this destructor was called as part of
- // the stack unwinding. Right now this means we cannot use this
- // mechanism in destructors, which is not a big deal, except for
- // one place: exception_guard. So for now we are going to have
- // this ugly special check which we will be able to get rid of
- // once C++17 uncaught_exceptions() becomes available.
+ // Don't flush the record if this destructor was called as part of the
+ // stack unwinding.
+ //
+#ifdef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+ if (uncaught_ == std::uncaught_exceptions ())
+ flush ();
+#else
+ // Fallback implementation. Right now this means we cannot use this
+ // mechanism in destructors, which is not a big deal, except for one
+ // place: exception_guard. Thus the ugly special check.
//
if (!std::uncaught_exception () || exception_unwinding_dtor)
flush ();
+#endif
}
}
diff --git a/butl/utility b/butl/utility
index c57aabb..02d9331 100644
--- a/butl/utility
+++ b/butl/utility
@@ -9,10 +9,11 @@
#include <cstddef> // size_t
#include <utility> // move(), forward()
#include <cstring> // strcmp(), strlen()
-#include <exception> // uncaught_exception()
+#include <exception> // uncaught_exception(s)()
//#include <functional> // hash
#include <butl/export>
+#include <butl/config>
namespace butl
{
@@ -153,15 +154,6 @@ namespace butl
// Call a function if there is an exception.
//
- // True means we are in the body of a destructor that is being called as
- // part of the exception stack unwindining. Used to compensate for the
- // deficiencies of uncaught_exception() until C++17 uncaught_exceptions()
- // becomes available.
- //
- // @@ MT: will have to be TLS.
- //
- LIBBUTL_EXPORT extern bool exception_unwinding_dtor;
-
template <typename F>
struct exception_guard;
@@ -172,6 +164,39 @@ namespace butl
return exception_guard<F> (std::move (f));
}
+#ifdef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+ template <typename F>
+ struct exception_guard
+ {
+ exception_guard (F f)
+ : f_ (std::move (f)),
+ u_ (std::uncaught_exceptions ()) {}
+
+ ~exception_guard ()
+ {
+ if (u_ != std::uncaught_exceptions ())
+ f_ ();
+ }
+
+ private:
+ F f_;
+ int u_;
+ };
+#else
+ // Fallback implementation using a TLS flag.
+ //
+ // True means we are in the body of a destructor that is being called as
+ // part of the exception stack unwindining.
+ //
+ LIBBUTL_EXPORT
+ extern
+#ifdef BUTL_CXX11_THREAD_LOCAL
+ thread_local
+#else
+ __thread
+#endif
+ bool exception_unwinding_dtor;
+
template <typename F>
struct exception_guard
{
@@ -189,6 +214,7 @@ namespace butl
private:
F f_;
};
+#endif
}
#include <butl/utility.ixx>
diff --git a/butl/utility.cxx b/butl/utility.cxx
index d6f418c..032d178 100644
--- a/butl/utility.cxx
+++ b/butl/utility.cxx
@@ -6,5 +6,12 @@
namespace butl
{
+#ifndef BUTL_CXX17_UNCAUGHT_EXCEPTIONS
+#ifdef BUTL_CXX11_THREAD_LOCAL
+ thread_local
+#else
+ __thread
+#endif
bool exception_unwinding_dtor = false;
+#endif
}