Platform and Compiler Support
-----------------------------
-libc++ is known to work on the following platforms, using gcc and
-clang.
-Note that functionality provided by ``<atomic>`` is only functional with clang
-and GCC.
+For using the libc++ headers
+############################
+The libc++ headers are known to work on the following platforms, using GCC and
+Clang. Note that functionality provided by ``<atomic>`` is only functional with
+Clang and GCC.
+
+============ ==================== ============
+OS Arch Compilers
+============ ==================== ============
+macOS 10.9+ i386, x86_64 Clang, GCC
+FreeBSD 10+ i386, x86_64, ARM Clang, GCC
+Linux i386, x86_64 Clang, GCC
+============ ==================== ============
+
+The following minimum compiler versions are required:
+
+* Clang 4.0 and above
+* GCC 5.0 and above.
+
+The C++03 dialect is only supported with Clang.
+
+For building the libc++ library
+###############################
+Building the libc++ library (static or shared) requires some features from
+the operating system. As such, it has its own set of (slightly different)
+system requirements.
============ ==================== ============ ========================
OS Arch Compilers ABI Library
============ ==================== ============ ========================
-macOS i386, x86_64 Clang, GCC libc++abi
+macOS 10.12+ i386, x86_64 Clang, GCC libc++abi
FreeBSD 10+ i386, x86_64, ARM Clang, GCC libcxxrt, libc++abi
Linux i386, x86_64 Clang, GCC libc++abi
============ ==================== ============ ========================
-The following minimum compiler versions are strongly recommended.
+The following minimum compiler versions are required:
* Clang 4.0 and above
* GCC 5.0 and above.
-The C++03 dialect is only supported for Clang compilers.
C++ Dialect Support
---------------------
#include "chrono"
#include "cerrno" // errno
#include "system_error" // __throw_system_error
-#include <time.h> // clock_gettime, CLOCK_MONOTONIC and CLOCK_REALTIME
+#include <time.h> // clock_gettime and CLOCK_{MONOTONIC,REALTIME,MONOTONIC_RAW}
#include "include/apple_availability.h"
#if __has_include(<unistd.h>)
#endif
#if defined(_LIBCPP_WIN32API)
-#define WIN32_LEAN_AND_MEAN
-#define VC_EXTRA_LEAN
-#include <windows.h>
-#if _WIN32_WINNT >= _WIN32_WINNT_WIN8
-#include <winapifamily.h>
-#endif
+# define WIN32_LEAN_AND_MEAN
+# define VC_EXTRA_LEAN
+# include <windows.h>
+# if _WIN32_WINNT >= _WIN32_WINNT_WIN8
+# include <winapifamily.h>
+# endif
#else
-#if !defined(CLOCK_REALTIME) || !defined(_LIBCPP_USE_CLOCK_GETTIME)
-#include <sys/time.h> // for gettimeofday and timeval
-#endif
+# if !defined(CLOCK_REALTIME)
+# include <sys/time.h> // for gettimeofday and timeval
+# endif // !defined(CLOCK_REALTIME)
#endif // defined(_LIBCPP_WIN32API)
-#if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK)
-#if __APPLE__
-#include <mach/mach_time.h> // mach_absolute_time, mach_timebase_info_data_t
-#elif !defined(_LIBCPP_WIN32API) && !defined(CLOCK_MONOTONIC)
-#error "Monotonic clock not implemented"
-#endif
-#endif
-
#if defined(__ELF__) && defined(_LIBCPP_LINK_RT_LIB)
-#pragma comment(lib, "rt")
+# pragma comment(lib, "rt")
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
static_cast<__int64>(ft.dwLowDateTime)};
return time_point(duration_cast<duration>(d - nt_to_unix_epoch));
#else
-#if defined(_LIBCPP_USE_CLOCK_GETTIME) && defined(CLOCK_REALTIME)
+#if defined(CLOCK_REALTIME)
struct timespec tp;
if (0 != clock_gettime(CLOCK_REALTIME, &tp))
__throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed");
timeval tv;
gettimeofday(&tv, 0);
return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
-#endif // _LIBCPP_USE_CLOCK_GETTIME && CLOCK_REALTIME
+#endif // CLOCK_REALTIME
#endif
}
#if defined(__APPLE__)
-// Darwin libc versions >= 1133 provide ns precision via CLOCK_MONOTONIC_RAW
-#if defined(_LIBCPP_USE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC_RAW)
+#if !defined(CLOCK_MONOTONIC_RAW)
+# error "Building libc++ on Apple platforms requires CLOCK_MONOTONIC_RAW"
+#endif
+
+// On Apple platforms, only CLOCK_UPTIME_RAW, CLOCK_MONOTONIC_RAW or
+// mach_absolute_time are able to time functions in the nanosecond range.
+// Furthermore, only CLOCK_MONOTONIC_RAW is truly monotonic, because it
+// also counts cycles when the system is asleep. Thus, it is the only
+// acceptable implementation of steady_clock.
steady_clock::time_point
steady_clock::now() _NOEXCEPT
{
return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
}
-#else
-// mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
-// nanoseconds since the computer booted up. MachInfo.numer and MachInfo.denom
-// are run time constants supplied by the OS. This clock has no relationship
-// to the Gregorian calendar. It's main use is as a high resolution timer.
-
-// MachInfo.numer / MachInfo.denom is often 1 on the latest equipment. Specialize
-// for that case as an optimization.
-
-static
-steady_clock::rep
-steady_simplified()
-{
- return static_cast<steady_clock::rep>(mach_absolute_time());
-}
-
-static
-double
-compute_steady_factor()
-{
- mach_timebase_info_data_t MachInfo;
- mach_timebase_info(&MachInfo);
- return static_cast<double>(MachInfo.numer) / MachInfo.denom;
-}
-
-static
-steady_clock::rep
-steady_full()
-{
- static const double factor = compute_steady_factor();
- return static_cast<steady_clock::rep>(mach_absolute_time() * factor);
-}
-
-typedef steady_clock::rep (*FP)();
-
-static
-FP
-init_steady_clock()
-{
- mach_timebase_info_data_t MachInfo;
- mach_timebase_info(&MachInfo);
- if (MachInfo.numer == MachInfo.denom)
- return &steady_simplified;
- return &steady_full;
-}
-
-steady_clock::time_point
-steady_clock::now() _NOEXCEPT
-{
- static FP fp = init_steady_clock();
- return time_point(duration(fp()));
-}
-#endif // defined(_LIBCPP_USE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC_RAW)
-
#elif defined(_LIBCPP_WIN32API)
// https://msdn.microsoft.com/en-us/library/windows/desktop/ms644905(v=vs.85).aspx says:
#elif defined(CLOCK_MONOTONIC)
-// On Apple platforms only CLOCK_UPTIME_RAW, CLOCK_MONOTONIC_RAW or
-// mach_absolute_time are able to time functions in the nanosecond range.
-// Thus, they are the only acceptable implementations of steady_clock.
-#ifdef __APPLE__
-#error "Never use CLOCK_MONOTONIC for steady_clock::now on Apple platforms"
-#endif
-
steady_clock::time_point
steady_clock::now() _NOEXCEPT
{
}
#else
-#error "Monotonic clock not implemented"
+# error "Monotonic clock not implemented"
#endif
#endif // !_LIBCPP_HAS_NO_MONOTONIC_CLOCK
#define _LIBCPP_USE_COPYFILE
#endif
-#if !defined(__APPLE__) && _POSIX_TIMERS > 0
-#define _LIBCPP_USE_CLOCK_GETTIME
-#endif
-
-#if !defined(CLOCK_REALTIME) || !defined(_LIBCPP_USE_CLOCK_GETTIME)
+#if !defined(CLOCK_REALTIME)
#include <sys/time.h> // for gettimeofday and timeval
-#endif // !defined(CLOCK_REALTIME)
+#endif // !defined(CLOCK_REALTIME)
#if defined(__ELF__) && defined(_LIBCPP_LINK_RT_LIB)
#pragma comment(lib, "rt")
_FilesystemClock::time_point _FilesystemClock::now() noexcept {
typedef chrono::duration<rep> __secs;
-#if defined(_LIBCPP_USE_CLOCK_GETTIME) && defined(CLOCK_REALTIME)
+#if defined(CLOCK_REALTIME)
typedef chrono::duration<rep, nano> __nsecs;
struct timespec tp;
if (0 != clock_gettime(CLOCK_REALTIME, &tp))
timeval tv;
gettimeofday(&tv, 0);
return time_point(__secs(tv.tv_sec) + __microsecs(tv.tv_usec));
-#endif // _LIBCPP_USE_CLOCK_GETTIME && CLOCK_REALTIME
+#endif // CLOCK_REALTIME
}
filesystem_error::~filesystem_error() {}
#endif // __ENVIRONMENT_.*_VERSION_MIN_REQUIRED__
#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
-#if __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101200
-#define _LIBCPP_USE_CLOCK_GETTIME
-#endif
-#elif defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__)
-#if __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 100000
-#define _LIBCPP_USE_CLOCK_GETTIME
-#endif
-#elif defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__)
-#if __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 100000
-#define _LIBCPP_USE_CLOCK_GETTIME
-#endif
-#elif defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__)
-#if __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 30000
-#define _LIBCPP_USE_CLOCK_GETTIME
-#endif
-#endif // __ENVIRONMENT_.*_VERSION_MIN_REQUIRED__
-
-#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
#if __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101500
#define _LIBCPP_USE_ULOCK
#endif