When trying to compile this one line with clang + libc++ (C++11 mode):
#include <boost/thread.hpp>
clang emits the following errors:
In file included from test.cpp:1:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread.hpp:13:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/thread.hpp:17:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/pthread/thread_data.hpp:11:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/locks.hpp:18:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/chrono/time_point.hpp:33:
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:353:49: error:
constexpr function never produces a constant expression
static BOOST_CHRONO_LIB_CONSTEXPR float lowest() ...
^
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:355:21: note:
non-constexpr function 'max' cannot be used in a constant expression
return -(std::numeric_limits::max) ();
^
/usr/bin/../lib/c++/v1/limits:443:43: note: declared here
_LIBCPP_INLINE_VISIBILITY static type max() _NOEXCEPT {return ...
^
In file included from test.cpp:1:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread.hpp:13:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/thread.hpp:17:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/pthread/thread_data.hpp:11:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/locks.hpp:18:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/chrono/time_point.hpp:33:
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:361:50: error:
constexpr function never produces a constant expression
static BOOST_CHRONO_LIB_CONSTEXPR double lowest() ...
^
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:363:21: note:
non-constexpr function 'max' cannot be used in a constant expression
return -(std::numeric_limits::max) ();
^
/usr/bin/../lib/c++/v1/limits:443:43: note: declared here
_LIBCPP_INLINE_VISIBILITY static type max() _NOEXCEPT {return ...
^
In file included from test.cpp:1:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread.hpp:13:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/thread.hpp:17:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/pthread/thread_data.hpp:11:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/thread/locks.hpp:18:
In file included from /Users/yongwei/Programming/boost_1_52_0/boost/chrono/time_point.hpp:33:
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:369:55: error:
constexpr function never produces a constant expression
static BOOST_CHRONO_LIB_CONSTEXPR long double lowest() ...
^
/Users/yongwei/Programming/boost_1_52_0/boost/chrono/duration.hpp:371:21: note:
non-constexpr function 'max' cannot be used in a constant expression
return -(std::numeric_limits::max)();
^
/usr/bin/../lib/c++/v1/limits:443:43: note: declared here
_LIBCPP_INLINE_VISIBILITY static type max() _NOEXCEPT {return ...
^
3 errors generated.
It looks to me this is a bug in libc++, because C++11 does require these functions to be constexpr.
Anyone encountered the same problem and can you concur? Do you know about any fixes?
My clang version is:
Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn) Target: x86_64-apple-darwin11.4.2 Thread model: posix
With Marx’s hint, I found a workaround. Defining
BOOST_NO_CXX11_NUMERIC_LIMITShelps in this case. So it does seem to be an incompleteness of libc++.According to Howard Hinnant, it is a bug of libc++, and is already fixed on the trunk. However, no info yet when Apple can release the fix into Xcode. I will mark the question answered for now.
EDIT: The issue is fixed in Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn). My current Xcode version is 4.6.3.