1 files changed, 44 insertions, 0 deletions
diff --git a/manual/creature.texi b/manual/creature.texi
index 705a949089..9fa658e9a7 100644
--- a/manual/creature.texi
+++ b/manual/creature.texi
@@ -165,6 +165,50 @@ This macro was introduced as part of the Large File Support extension
 (LFS).
 @end defvr
 
+@defvr Macro _TIME_BITS
+This macro determines the bit size of @code{time_t} (and therefore the
+bit size of all @code{time_t} derived types and the prototypes of all
+related functions).  If @code{_TIME_BITS} is undefined, the bit size of
+@code{time_t} is architecture dependent.
+
+Possible values of @code{_TIME_BITS}:
+@enumerate
+@item
+@code{_TIME_BITS=64} and port from the outset uses 64-bit
+@code{time_t} and word size equals to @w{64 bits} (e.g. x86_64) - no
+action
+
+@item
+@code{_TIME_BITS=32} and port from the outset uses 32-bit
+@code{time_t} and word size equals to @w{64 bits} (e.g. ARM) - no
+action
+
+@item
+@code{_TIME_BITS=64} and port from the outset uses 64-bit
+@code{time_t} and word size equals to @w{32 bits} (e.g. ARC, RV32)
+- no action
+
+@item
+@code{_TIME_BITS=64} and port from the outset uses 32-bit
+@code{time_t} and word size equals to @w{32 bits} (e.g. ARM)
+- the @code{time_t} is modified to be able to hold 64-bit time.
+
+@item
+For any other use case the compile-time error is emitted.
+@end enumerate
+
+The @code{_TIME_BITS} can be only used when @code{_FILE_OFFSET_BITS=64}
+is also defined.
+
+For the point @b{4} above, calls to proper syscalls depend on the
+Linux kernel version on which the system is running. For Linux kernel
+version above @b{5.1} syscalls supporting 64-bit time are used. Otherwise,
+a fallback code is used with legacy (i.e. 32-bit) syscalls.
+
+By using this macro certain ports gain support for 64-bit time and as
+a result become immune to Y2038 problem.
+@end defvr
+
 @defvr Macro _ISOC99_SOURCE
 @standards{GNU, (none)}
 If this macro is defined, features from ISO C99 are included.  Since