On 2012-07-07 22:01, Howard Hinnant wrote:
Author: hhinnant
Date: Sat Jul 7 15:01:52 2012
New Revision: 159901
URL: http://llvm.org/viewvc/llvm-project?rev=159901&view=rev
Log:
Apply constexpr to the mutex constructor. As a conforming extension, apply
constexpr to the condition_variable constructor. These are important because
it enables the compiler to construct these types at compile time, even though
the object will be non-const. Since they are constructed at compile time,
there is no chance of a data race before they are constructed.
...
+#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+ constexpr mutex() : __m_ PTHREAD_MUTEX_INITIALIZER {}
+#else
mutex() {__m_ = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;}
+#endif
...
+#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+ constexpr condition_variable() : __cv_ PTHREAD_COND_INITIALIZER {}
+#else
condition_variable() {__cv_ = (pthread_cond_t)PTHREAD_COND_INITIALIZER;}
+#endif
On FreeBSD, PTHREAD_MUTEX_INITIALIZER and PTHREAD_COND_INITIALIZER are
both defined as NULL, which ends up as nullptr if you are using
-std=c++0x or higher. This leads to compilation errors:
/usr/include/c++/v1/__mutex_base:45:14: error: expected '{' or ','
~mutex();
^
/usr/include/c++/v1/__mutex_base:311:26: error: expected '{' or ','
~condition_variable();
^
Benjamin Kramer suggested to use parentheses around the initializers, as
per the attached patch. He checked that this works on OSX, and I can
verify it works on FreeBSD.
Index: include/__mutex_base
===================================================================
--- include/__mutex_base (revision 163535)
+++ include/__mutex_base (working copy)
@@ -39,11 +39,11 @@ class _LIBCPP_VISIBLE mutex
public:
_LIBCPP_INLINE_VISIBILITY
#ifndef _LIBCPP_HAS_NO_CONSTEXPR
- constexpr mutex() _NOEXCEPT : __m_ PTHREAD_MUTEX_INITIALIZER {}
+ constexpr mutex() _NOEXCEPT : __m_(PTHREAD_MUTEX_INITIALIZER) {}
#else
mutex() _NOEXCEPT {__m_ = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;}
#endif
- ~mutex();
+ ~mutex(){}
private:
mutex(const mutex&);// = delete;
@@ -305,7 +305,7 @@ class _LIBCPP_VISIBLE condition_variable
public:
_LIBCPP_INLINE_VISIBILITY
#ifndef _LIBCPP_HAS_NO_CONSTEXPR
- constexpr condition_variable() : __cv_ PTHREAD_COND_INITIALIZER {}
+ constexpr condition_variable() : __cv_(PTHREAD_COND_INITIALIZER) {}
#else
condition_variable() {__cv_ = (pthread_cond_t)PTHREAD_COND_INITIALIZER;}
#endif
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