+2023-07-29 Paul Eggert <eggert@cs.ucla.edu>
+
+ readutmp: work around glibc utmpx bug
+ When compiled with _TIME_BITS=64, glibc <utmpx.h> does not work,
+ because the files use 32-bit time_t and the code passes this to
+ the user unmodified, but <utmpx.h> defines a struct with 64-bit
+ time_t. Work around this compatibility bug.
+ * lib/readutmp.c (copy_utmp_entry): New function.
+ (read_utmp): Use it.
+
2023-07-29 Bruno Haible <bruno@clisp.org>
time-h: Obey GNULIB_POSIXCHECK, not GNULIB_PORTCHECK.
@item
This function is missing on some platforms:
FreeBSD 13.0, OpenBSD 6.7, Minix 3.1.8, AIX 5.1, HP-UX 11, Cygwin 2.9, mingw, MSVC 14, Android 9.0.
+@item
+On some platforms, this function 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.
+@item
+On some platforms, this function misbehaves if the @code{year2038} or
+@code{year2038-recommended} modules are used and the program is
+configured without the @option{--disable-year2038} option.
+The @code{readutmp} module works around this problem:
+glibc 2.38 on 32-bit platforms like x86 and ARM where @code{time_t}
+was historically 32 bits.
+@xref{Avoiding the year 2038 problem}.
@end itemize
@item
This function is missing on some platforms:
FreeBSD 13.0, OpenBSD 6.7, Minix 3.1.8, AIX 5.1, HP-UX 11, Cygwin 2.9, mingw, MSVC 14, Android 9.0.
+@item
+On some platforms, this function 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.
+@item
+On some platforms, this function misbehaves if the @code{year2038} or
+@code{year2038-recommended} modules are used and the program is
+configured without the @option{--disable-year2038} option.
+The @code{readutmp} module works around this problem:
+glibc 2.38 on 32-bit platforms like x86 and ARM where @code{time_t}
+was historically 32 bits.
+@xref{Avoiding the year 2038 problem}.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
+@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.
+@item
+On some platforms, this header misbehaves if the @code{year2038} or
+@code{year2038-recommended} modules are used and the program is
+configured without the @option{--disable-year2038} option.
+The @code{readutmp} module works around this problem:
+glibc 2.38 on 32-bit platforms like x86 and ARM where @code{time_t}
+was historically 32 bits.
+@xref{Avoiding the year 2038 problem}.
@end itemize
@item
This header file is missing on some platforms:
FreeBSD 6.0, OpenBSD 6.7, Minix 3.1.8, mingw, MSVC 14, Android 9.0.
+@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.
+@item
+On some platforms, this header misbehaves if the @code{year2038} or
+@code{year2038-recommended} modules are used and the program is
+configured without the @option{--disable-year2038} option.
+The @code{readutmp} module works around this problem:
+glibc 2.38 on 32-bit platforms like x86 and ARM where @code{time_t}
+was historically 32 bits.
+@xref{Avoiding the year 2038 problem}.
@end itemize
@item
Haiku/x86.
@end itemize
+
+If you use the @samp{year2038} or @samp{year2038-recommended} modules,
+and configure to support timestamps after the year 2038,
+your code should not include @samp{<utmp.h>} or @samp{<utmpx.h>}
+directly, because these include files do not work with 64-bit timestamps
+if the platform's @code{time_t} was traditionally 32 bits.
+Your code can instead use the @samp{readutmp} module,
+which works around this problem.
#ifdef UTMP_NAME_FUNCTION
+static void
+copy_utmp_entry (STRUCT_UTMP *dst, STRUCT_UTMP *src)
+{
+#if __GLIBC__ && _TIME_BITS == 64
+ /* Convert from external form in SRC to internal form in DST.
+ It is OK to convert now, rather than earlier, before
+ desirable_utmp_entry was invoked, because desirable_utmp_entry
+ inspects only the leading prefix of the entry, which is the
+ same in both external and internal forms. */
+
+ /* This is a near-copy of glibc's struct utmpx, which stops working
+ after the year 2038. Unlike the glibc version, struct utmpx32
+ describes the file format even if time_t is 64 bits. */
+ struct utmpx32
+ {
+ short int ut_type; /* Type of login. */
+ pid_t ut_pid; /* Process ID of login process. */
+ char ut_line[sizeof src->ut_line]; /* Devicename. */
+ char ut_id[sizeof src->ut_id]; /* Inittab ID. */
+ char ut_user[sizeof src->ut_user]; /* Username. */
+ char ut_host[sizeof src->ut_host]; /* Hostname for remote login. */
+ struct __exit_status ut_exit; /* Exit status of a process marked
+ as DEAD_PROCESS. */
+ /* The fields ut_session and ut_tv must be the same size when compiled
+ 32- and 64-bit. This allows files and shared memory to be shared
+ between 32- and 64-bit applications. */
+ int ut_session; /* Session ID, used for windowing. */
+ struct
+ {
+ int tv_sec; /* Seconds. */
+ int tv_usec; /* Microseconds. */
+ } ut_tv; /* Time entry was made. */
+ int ut_addr_v6[4]; /* Internet address of remote host. */
+ char ut_reserved[20]; /* Reserved for future use. */
+ } *s = (struct utmpx32 *) src;
+ memcpy (dst, s, offsetof (struct utmpx32, ut_session));
+ dst->ut_session = s->ut_session;
+ dst->ut_tv.tv_sec = s->ut_tv.tv_sec;
+ dst->ut_tv.tv_usec = s->ut_tv.tv_usec;
+ memcpy (&dst->ut_addr_v6, s->ut_addr_v6, sizeof dst->ut_addr_v6);
+#else
+ *dst = *src;
+#endif
+}
+
int
read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
int options)
if (n_read == n_alloc)
utmp = xpalloc (utmp, &n_alloc, 1, -1, sizeof *utmp);
- utmp[n_read++] = *u;
+ copy_utmp_entry (&utmp[n_read++], u);
}
END_UTMP_ENT ();