[PATCH] * doc/posix-headers/utmpx.texi: Update for glibc.

[Paul Eggert]

---
 doc/posix-headers/utmpx.texi | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/doc/posix-headers/utmpx.texi b/doc/posix-headers/utmpx.texi
index ac2404bdc4..be1a9018ec 100644
--- a/doc/posix-headers/utmpx.texi
+++ b/doc/posix-headers/utmpx.texi
@@ -29,10 +29,20 @@ The @code{struct utmpx} field @code{ut_addr} or 
@code{ut_addr_v6} or
 @code{ut_ss} does not exist on some platforms:
 macOS, FreeBSD, AIX, Solaris.
 @item
+On some platforms, the @code{struct utmpx} field @code{ut_tv} is not
+of type @code{struct timeval}.  Instead, it is a different
+struct with @code{tv_sec} and @code{tv_usec} members that may
+have different types than the members of @code{struct timeval}:
+glibc 2.39 on platforms where @code{time_t} was historically 32 bits
+and where log file formats were not changed when 64-bit @code{time_t}
+was introduced.
+@item
 On some platforms, this API does not support timestamps past the
 year 2038:
-glibc 2.38 on 32-bit platforms like x86 and ARM where @code{time_t}
-was historically 32 bits.
+glibc 2.39 on 32-bit platforms like x86 and ARM where @code{time_t}
+was historically 32 bits; however, glibc 2.40 is planned to support
+timestamps up to the year 2106, by changing @code{ut_tv.tv_sec}'s type
+to be a 32-bit unsigned integer.
 @item
 On some platforms, this header misbehaves if the @code{year2038} or
 @code{year2038-recommended} modules are used and the program is
-- 
2.44.0