libstdc++: Revert changes for SYS_clock_gettime64 [PR 93421]
As discussed in the PR, it's incredibly unlikely that a system that needs to use the SYS_clock_gettime syscall (e.g. glibc 2.16 or older) is going to define the SYS_clock_gettime64 macro. Ancient systems that need to use the syscall aren't going to have time64 support. This reverts the recent changes to try and make clock_gettime syscalls be compatible with systems that have been updated for time64 (those changes were wrong anyway as they misspelled the SYS_clock_gettime64 macro). The changes for futex syscalls are retained, because we still use them on modern systems that might be using time64. To ensure that the clock_gettime syscalls are safe, configure will fail if SYS_clock_gettime is needed, and SYS_clock_gettime64 is also defined (but to a distinct value from SYS_clock_gettime), and the tv_sec member of timespec is larger than long. This means we will be unable to build on a hypothetical system where we need the time32 version of SYS_clock_gettime but where userspace is using a time64 struct timespec. In the unlikely event that this failure is triggered on any real systems, we can fix it later. But we probably won't need to. libstdc++-v3/ChangeLog: PR libstdc++/93421 * acinclude.m4 (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Fail if struct timespec isn't compatible with SYS_clock_gettime. * configure: Regenerate. * src/c++11/chrono.cc: Revert changes for time64 compatibility. Add static_assert instead. * src/c++11/futex.cc (_M_futex_wait_until_steady): Assume SYS_clock_gettime can use struct timespec.
This commit is contained in:
Jonathan Wakely
parent
61ef34c503
commit
1e3e6c700f
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@ -1561,13 +1561,34 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
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#endif
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syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &tp);
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syscall(SYS_clock_gettime, CLOCK_REALTIME, &tp);
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], [ac_has_clock_monotonic_syscall=yes], [ac_has_clock_monotonic_syscall=no])
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AC_MSG_RESULT($ac_has_clock_monotonic_syscall)
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if test x"$ac_has_clock_monotonic_syscall" = x"yes"; then
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], [ac_has_clock_gettime_syscall=yes], [ac_has_clock_gettime_syscall=no])
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AC_MSG_RESULT($ac_has_clock_gettime_syscall)
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if test x"$ac_has_clock_gettime_syscall" = x"yes"; then
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AC_DEFINE(_GLIBCXX_USE_CLOCK_GETTIME_SYSCALL, 1,
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[ Defined if clock_gettime syscall has monotonic and realtime clock support. ])
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[Defined if clock_gettime syscall has monotonic and realtime clock support. ])
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ac_has_clock_monotonic=yes
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ac_has_clock_realtime=yes
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AC_MSG_CHECKING([for struct timespec that matches syscall])
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AC_TRY_COMPILE(
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[#include <time.h>
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#include <sys/syscall.h>
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],
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[#ifdef SYS_clock_gettime64
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#if SYS_clock_gettime64 != SYS_clock_gettime
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// We need to use SYS_clock_gettime and libc appears to
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// also know about the SYS_clock_gettime64 syscall.
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// Check that userspace doesn't use time64 version of timespec.
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static_assert(sizeof(timespec::tv_sec) == sizeof(long),
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"struct timespec must be compatible with SYS_clock_gettime");
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#endif
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#endif
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],
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[ac_timespec_matches_syscall=yes],
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[ac_timespec_matches_syscall=no])
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AC_MSG_RESULT($ac_timespec_matches_syscall)
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if test x"$ac_timespec_matches_syscall" = no; then
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AC_MSG_ERROR([struct timespec is not compatible with SYS_clock_gettime, please report a bug to http://gcc.gnu.org/bugzilla])
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fi
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fi;;
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esac
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fi
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@ -21661,19 +21661,54 @@ main ()
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}
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_ACEOF
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if ac_fn_cxx_try_compile "$LINENO"; then :
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ac_has_clock_monotonic_syscall=yes
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ac_has_clock_gettime_syscall=yes
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else
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ac_has_clock_monotonic_syscall=no
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ac_has_clock_gettime_syscall=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_has_clock_monotonic_syscall" >&5
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$as_echo "$ac_has_clock_monotonic_syscall" >&6; }
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if test x"$ac_has_clock_monotonic_syscall" = x"yes"; then
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_has_clock_gettime_syscall" >&5
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$as_echo "$ac_has_clock_gettime_syscall" >&6; }
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if test x"$ac_has_clock_gettime_syscall" = x"yes"; then
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$as_echo "#define _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL 1" >>confdefs.h
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ac_has_clock_monotonic=yes
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ac_has_clock_realtime=yes
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for struct timespec that matches syscall" >&5
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$as_echo_n "checking for struct timespec that matches syscall... " >&6; }
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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#include <time.h>
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#include <sys/syscall.h>
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int
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main ()
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{
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#ifdef SYS_clock_gettime64
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#if SYS_clock_gettime64 != SYS_clock_gettime
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// We need to use SYS_clock_gettime and libc appears to
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// also know about the SYS_clock_gettime64 syscall.
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// Check that userspace doesn't use time64 version of timespec.
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static_assert(sizeof(timespec::tv_sec) == sizeof(long),
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"struct timespec must be compatible with SYS_clock_gettime");
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#endif
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#endif
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;
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return 0;
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}
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_ACEOF
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if ac_fn_cxx_try_compile "$LINENO"; then :
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ac_timespec_matches_syscall=yes
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else
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ac_timespec_matches_syscall=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_timespec_matches_syscall" >&5
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$as_echo "$ac_timespec_matches_syscall" >&6; }
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if test x"$ac_timespec_matches_syscall" = no; then
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as_fn_error $? "struct timespec is not compatible with SYS_clock_gettime, please report a bug to http://gcc.gnu.org/bugzilla" "$LINENO" 5
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fi
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fi;;
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esac
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fi
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@ -35,17 +35,6 @@
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#ifdef _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL
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#include <unistd.h>
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#include <sys/syscall.h>
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# if defined(SYS_clock_gettime_time64) \
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&& SYS_clock_gettime_time64 != SYS_clock_gettime
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// Userspace knows about the new time64 syscalls, so it's possible that
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// userspace has also updated timespec to use a 64-bit tv_sec.
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// The SYS_clock_gettime syscall still uses the old definition
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// of timespec where tv_sec is 32 bits, so define a type that matches that.
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struct syscall_timespec { long tv_sec; long tv_nsec; };
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# else
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using syscall_timespec = ::timespec;
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# endif
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#endif
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namespace std _GLIBCXX_VISIBILITY(default)
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@ -63,12 +52,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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system_clock::now() noexcept
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{
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#ifdef _GLIBCXX_USE_CLOCK_REALTIME
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timespec tp;
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// -EINVAL, -EFAULT
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#ifdef _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL
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syscall_timespec tp;
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syscall(SYS_clock_gettime, CLOCK_REALTIME, &tp);
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#else
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timespec tp;
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clock_gettime(CLOCK_REALTIME, &tp);
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#endif
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return time_point(duration(chrono::seconds(tp.tv_sec)
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@ -92,12 +80,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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steady_clock::now() noexcept
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{
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#ifdef _GLIBCXX_USE_CLOCK_MONOTONIC
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timespec tp;
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// -EINVAL, -EFAULT
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#ifdef _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL
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syscall_timespec tp;
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syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &tp);
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#else
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timespec tp;
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clock_gettime(CLOCK_MONOTONIC, &tp);
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#endif
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return time_point(duration(chrono::seconds(tp.tv_sec)
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@ -61,8 +61,8 @@ namespace
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#if defined(SYS_futex_time64) && SYS_futex_time64 != SYS_futex
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// Userspace knows about the new time64 syscalls, so it's possible that
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// userspace has also updated timespec to use a 64-bit tv_sec.
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// The SYS_futex and SYS_clock_gettime syscalls still use the old definition
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// of timespec where tv_sec is 32 bits, so define a type that matches that.
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// The SYS_futex syscall still uses the old definition of timespec
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// where tv_sec is 32 bits, so define a type that matches that.
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struct syscall_timespec { long tv_sec; long tv_nsec; };
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#else
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using syscall_timespec = ::timespec;
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@ -234,11 +234,10 @@ namespace
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// We only get to here if futex_clock_monotonic_unavailable was
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// true or has just been set to true.
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struct timespec ts;
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#ifdef _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL
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syscall_timespec ts;
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syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
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#else
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struct timespec ts;
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clock_gettime(CLOCK_MONOTONIC, &ts);
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#endif
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