Y2038: add function __localtime64
Tested with 'make check' on x86_64-linux-gnu and i686-linux.gnu. * include/time.h (__localtime64): Add. * manual/maint.texi: Document Y2038 symbol handling. * time/localtime.c (__localtime64): Add. [__TIMERSIZE != 64] (__localtime): Turn into a wrapper.
This commit is contained in:
Albert ARIBAUD (3ADEV)
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@ -1,3 +1,12 @@
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2018-12-17 Albert ARIBAUD <albert.aribaud@3adev.fr>
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* include/time.h
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(__localtime64): Add.
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* manual/maint.texi: Document Y2038 symbol handling.
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* time/localtime.c
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(__localtime64): Add.
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[__TIMERSIZE != 64] (__localtime): Turn into a wrapper.
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2018-12-17 Joseph Myers <joseph@codesourcery.com>
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* sysdeps/unix/sysv/linux/ia64/sysdep.h (ASM_CLOBBERS_6_COMMON):
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@ -56,6 +56,14 @@ extern time_t __mktime_internal (struct tm *__tp,
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struct tm *(*__func) (const time_t *,
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struct tm *),
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long int *__offset) attribute_hidden;
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#if __TIMESIZE == 64
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# define __localtime64 localtime
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#else
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extern struct tm *__localtime64 (const __time64_t *__timer);
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libc_hidden_proto (__localtime64)
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#endif
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extern struct tm *__localtime_r (const time_t *__timer,
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struct tm *__tp) attribute_hidden;
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@ -5,6 +5,7 @@
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@menu
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* Source Layout:: How to add new functions or header files
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to the GNU C Library.
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* Symbol handling:: How to handle symbols in the GNU C Library.
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* Porting:: How to port the GNU C Library to
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a new machine or operating system.
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@end menu
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@ -183,6 +184,130 @@ header file in the machine-specific directory, e.g.,
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@file{sysdeps/powerpc/sys/platform/ppc.h}.
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@node Symbol handling
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@appendixsec Symbol handling in the GNU C Library
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@menu
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* 64-bit time symbol handling :: How to handle 64-bit time related
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symbols in the GNU C Library.
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@end menu
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@node 64-bit time symbol handling
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@appendixsubsec 64-bit time symbol handling in the GNU C Library
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With respect to time handling, @theglibcadj{} configurations fall in two
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classes depending on the value of @code{__TIMESIZE}:
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@table @code
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@item @code{__TIMESIZE == 32}
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These @dfn{dual-time} configurations have both 32-bit and 64-bit time
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support. 32-bit time support provides type @code{time_t} and cannot
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handle dates beyond @dfn{Y2038}. 64-bit time support provides type
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@code{__time64_t} and can handle dates beyond @dfn{Y2038}.
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In these configurations, time-related types have two declarations,
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a 64-bit one, and a 32-bit one; and time-related functions generally
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have two definitions: a 64-bit one, and a 32-bit one which is a wrapper
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around the former. Therefore, for every @code{time_t}-related symbol,
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there is a corresponding @code{__time64_t}-related symbol, the name of
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which is usually the 32-bit symbol's name with @code{__} (a double
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underscore) prepended and @code{64} appended. For instance, the
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64-bit-time counterpart of @code{clock_gettime} is
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@code{__clock_gettime64}.
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@item @code{__TIMESIZE == 64}
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These @dfn{single-time} configurations only have a 64-bit @code{time_t}
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and related functions, which can handle dates beyond 2038-01-19
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03:14:07 (aka @dfn{Y2038}).
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In these configurations, time-related types only have a 64-bit
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declaration; and time-related functions only have one 64-bit definition.
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However, for every @code{time_t}-related symbol, there is a
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corresponding @code{__time64_t}-related macro, the name of which is
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derived as in the dual-time configuration case, and which expands to
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the symbol's name. For instance, the macro @code{__clock_gettime64}
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expands to @code{clock_gettime}.
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These macros are purely internal to @theglibc{} and exist only so that
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a single definition of the 64-bit time functions can be used on both
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single-time and dual-time configurations, and so that glibc code can
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freely call the 64-bit functions internally in all configurations.
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@end table
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@c The following paragraph should be removed once external interfaces
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@c get support for both time sizes.
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Note: at this point, 64-bit time support in dual-time configurations is
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work-in-progress, so for these configurations, the public API only makes
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the 32-bit time support available. In a later change, the public API
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will allow user code to choose the time size for a given compilation
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unit.
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64-bit variants of time-related types or functions are defined for all
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configurations and use 64-bit-time symbol names (for dual-time
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configurations) or macros (for single-time configurations).
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32-bit variants of time-related types or functions are defined only for
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dual-time configurations.
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Here is an example with @code{localtime}:
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Function @code{localtime} is declared in @file{time/time.h} as
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@smallexample
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extern struct tm *localtime (const time_t *__timer) __THROW;
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libc_hidden_proto (localtime)
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@end smallexample
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For single-time configurations, @code{__localtime64} is a macro which
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evaluates to @code{localtime}; for dual-time configurations,
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@code{__localtime64} is a function similar to @code{localtime} except
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it uses Y2038-proof types:
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@smallexample
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#if __TIMESIZE == 64
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# define __localtime64 localtime
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#else
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extern struct tm *__localtime64 (const __time64_t *__timer) __THROW;
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libc_hidden_proto (__localtime64)
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#endif
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@end smallexample
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(note: type @code{time_t} is replaced with @code{__time64_t} because
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@code{time_t} is not Y2038-proof, but @code{struct tm} is not
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replaced because it is already Y2038-proof.)
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The 64-bit-time implementation of @code{localtime} is written as follows
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and is compiled for both dual-time and single-time configuration classes.
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@smallexample
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struct tm *
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__localtime64 (const __time64_t *t)
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@lbracechar{}
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return __tz_convert (*t, 1, &_tmbuf);
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@rbracechar{}
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libc_hidden_def (__localtime64)
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@end smallexample
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The 32-bit-time implementation is a wrapper and is only compiled for
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dual-time configurations:
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@smallexample
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#if __TIMESIZE != 64
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struct tm *
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localtime (const time_t *t)
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@lbracechar{}
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__time64_t t64 = *t;
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return __localtime64 (&t64);
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@rbracechar{}
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libc_hidden_def (localtime)
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#endif
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@end smallexample
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@node Porting
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@appendixsec Porting @theglibc{}
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@ -34,8 +34,22 @@ weak_alias (__localtime_r, localtime_r)
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/* Return the `struct tm' representation of *T in local time. */
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struct tm *
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localtime (const time_t *t)
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__localtime64 (const __time64_t *t)
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{
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return __tz_convert (*t, 1, &_tmbuf);
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}
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libc_hidden_def (__localtime64)
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/* Provide a 32-bit variant if needed. */
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#if __TIMESIZE != 64
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struct tm *
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localtime (const time_t *t)
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{
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__time64_t t64 = *t;
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return __localtime64 (&t64);
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}
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libc_hidden_def (localtime)
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#endif
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