diff options
| -rw-r--r-- | ChangeLog | 9 | ||||
| -rw-r--r-- | include/time.h | 8 | ||||
| -rw-r--r-- | manual/maint.texi | 125 | ||||
| -rw-r--r-- | time/localtime.c | 16 |
4 files changed, 157 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog index 10eba56bb6..e7316013b6 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,12 @@ +2018-12-17 Albert ARIBAUD <albert.aribaud@3adev.fr> + + * include/time.h + (__localtime64): Add. + * manual/maint.texi: Document Y2038 symbol handling. + * time/localtime.c + (__localtime64): Add. + [__TIMERSIZE != 64] (__localtime): Turn into a wrapper. + 2018-12-17 Joseph Myers <joseph@codesourcery.com> * sysdeps/unix/sysv/linux/ia64/sysdep.h (ASM_CLOBBERS_6_COMMON): diff --git a/include/time.h b/include/time.h index 37964f7b76..3bc303a36e 100644 --- a/include/time.h +++ b/include/time.h @@ -56,6 +56,14 @@ extern time_t __mktime_internal (struct tm *__tp, struct tm *(*__func) (const time_t *, struct tm *), long int *__offset) attribute_hidden; + +#if __TIMESIZE == 64 +# define __localtime64 localtime +#else +extern struct tm *__localtime64 (const __time64_t *__timer); +libc_hidden_proto (__localtime64) +#endif + extern struct tm *__localtime_r (const time_t *__timer, struct tm *__tp) attribute_hidden; diff --git a/manual/maint.texi b/manual/maint.texi index fce06bfa88..d516a90293 100644 --- a/manual/maint.texi +++ b/manual/maint.texi @@ -5,6 +5,7 @@ @menu * Source Layout:: How to add new functions or header files to the GNU C Library. +* Symbol handling:: How to handle symbols in the GNU C Library. * Porting:: How to port the GNU C Library to a new machine or operating system. @end menu @@ -183,6 +184,130 @@ header file in the machine-specific directory, e.g., @file{sysdeps/powerpc/sys/platform/ppc.h}. +@node Symbol handling +@appendixsec Symbol handling in the GNU C Library + +@menu +* 64-bit time symbol handling :: How to handle 64-bit time related + symbols in the GNU C Library. +@end menu + +@node 64-bit time symbol handling +@appendixsubsec 64-bit time symbol handling in the GNU C Library + +With respect to time handling, @theglibcadj{} configurations fall in two +classes depending on the value of @code{__TIMESIZE}: + +@table @code + +@item @code{__TIMESIZE == 32} + +These @dfn{dual-time} configurations have both 32-bit and 64-bit time +support. 32-bit time support provides type @code{time_t} and cannot +handle dates beyond @dfn{Y2038}. 64-bit time support provides type +@code{__time64_t} and can handle dates beyond @dfn{Y2038}. + +In these configurations, time-related types have two declarations, +a 64-bit one, and a 32-bit one; and time-related functions generally +have two definitions: a 64-bit one, and a 32-bit one which is a wrapper +around the former. Therefore, for every @code{time_t}-related symbol, +there is a corresponding @code{__time64_t}-related symbol, the name of +which is usually the 32-bit symbol's name with @code{__} (a double +underscore) prepended and @code{64} appended. For instance, the +64-bit-time counterpart of @code{clock_gettime} is +@code{__clock_gettime64}. + +@item @code{__TIMESIZE == 64} + +These @dfn{single-time} configurations only have a 64-bit @code{time_t} +and related functions, which can handle dates beyond 2038-01-19 +03:14:07 (aka @dfn{Y2038}). + +In these configurations, time-related types only have a 64-bit +declaration; and time-related functions only have one 64-bit definition. +However, for every @code{time_t}-related symbol, there is a +corresponding @code{__time64_t}-related macro, the name of which is +derived as in the dual-time configuration case, and which expands to +the symbol's name. For instance, the macro @code{__clock_gettime64} +expands to @code{clock_gettime}. + +These macros are purely internal to @theglibc{} and exist only so that +a single definition of the 64-bit time functions can be used on both +single-time and dual-time configurations, and so that glibc code can +freely call the 64-bit functions internally in all configurations. + +@end table + +@c The following paragraph should be removed once external interfaces +@c get support for both time sizes. + +Note: at this point, 64-bit time support in dual-time configurations is +work-in-progress, so for these configurations, the public API only makes +the 32-bit time support available. In a later change, the public API +will allow user code to choose the time size for a given compilation +unit. + +64-bit variants of time-related types or functions are defined for all +configurations and use 64-bit-time symbol names (for dual-time +configurations) or macros (for single-time configurations). + +32-bit variants of time-related types or functions are defined only for +dual-time configurations. + +Here is an example with @code{localtime}: + +Function @code{localtime} is declared in @file{time/time.h} as +@smallexample +extern struct tm *localtime (const time_t *__timer) __THROW; +libc_hidden_proto (localtime) +@end smallexample + +For single-time configurations, @code{__localtime64} is a macro which +evaluates to @code{localtime}; for dual-time configurations, +@code{__localtime64} is a function similar to @code{localtime} except +it uses Y2038-proof types: +@smallexample +#if __TIMESIZE == 64 +# define __localtime64 localtime +#else +extern struct tm *__localtime64 (const __time64_t *__timer) __THROW; +libc_hidden_proto (__localtime64) +#endif +@end smallexample + +(note: type @code{time_t} is replaced with @code{__time64_t} because +@code{time_t} is not Y2038-proof, but @code{struct tm} is not +replaced because it is already Y2038-proof.) + +The 64-bit-time implementation of @code{localtime} is written as follows +and is compiled for both dual-time and single-time configuration classes. + +@smallexample +struct tm * +__localtime64 (const __time64_t *t) +@lbracechar{} + return __tz_convert (*t, 1, &_tmbuf); +@rbracechar{} +libc_hidden_def (__localtime64) +@end smallexample + +The 32-bit-time implementation is a wrapper and is only compiled for +dual-time configurations: + +@smallexample +#if __TIMESIZE != 64 + +struct tm * +localtime (const time_t *t) +@lbracechar{} + __time64_t t64 = *t; + return __localtime64 (&t64); +@rbracechar{} +libc_hidden_def (localtime) + +#endif +@end smallexample + @node Porting @appendixsec Porting @theglibc{} diff --git a/time/localtime.c b/time/localtime.c index 92dbfe0f8c..96879d4ec0 100644 --- a/time/localtime.c +++ b/time/localtime.c @@ -34,8 +34,22 @@ weak_alias (__localtime_r, localtime_r) /* Return the `struct tm' representation of *T in local time. */ struct tm * -localtime (const time_t *t) +__localtime64 (const __time64_t *t) { return __tz_convert (*t, 1, &_tmbuf); } +libc_hidden_def (__localtime64) + +/* Provide a 32-bit variant if needed. */ + +#if __TIMESIZE != 64 + +struct tm * +localtime (const time_t *t) +{ + __time64_t t64 = *t; + return __localtime64 (&t64); +} libc_hidden_def (localtime) + +#endif |