time: New module.

* lib/time.in.h (time): New declaration.
* lib/time.c: New file.
* m4/time_h.m4 (gl_TIME_H_REQUIRE_DEFAULTS): Initialize GNULIB_TIME.
(gl_TIME_H_DEFAULTS): Initialize REPLACE_TIME.
* m4/time.m4: New file.
* modules/time-h (Makefile.am): Substitute GNULIB_TIME, REPLACE_TIME.
* modules/time: New file.
* tests/test-time-h-c++.cc: Check the signature of
GNULIB_NAMESPACE::time.
* doc/posix-functions/time.texi: Mention the glibc problem and the
'time' module.

2 files changed, 46 insertions, 1 deletions

diff --git a/m4/time.m4 b/m4/time.m4
new file mode 100644
index 0000000000..0dbb6011ed
--- /dev/null
+++ b/m4/time.m4
@@ -0,0 +1,43 @@
+# time.m4 serial 1
+dnl Copyright (C) 2023 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Bruno Haible.
+
+AC_DEFUN([gl_FUNC_TIME],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  dnl glibc has the bug https://sourceware.org/bugzilla/show_bug.cgi?id=30200 .
+  AC_CACHE_CHECK([whether time() works],
+    [gl_cv_func_time_works],
+    [dnl Guess that it works except on glibc >= 2.31 with Linux.
+     dnl And binaries produced on glibc < 2.31 need to run fine on newer
+     dnl glibc versions as well; therefore ignore __GLIBC_MINOR__.
+     case "$host_os" in
+       linux*-gnu*)
+         AC_EGREP_CPP([Unlucky], [
+           #include <features.h>
+           #ifdef __GNU_LIBRARY__
+            #if __GLIBC__ == 2
+             Unlucky GNU user
+            #endif
+           #endif
+           ],
+           [gl_cv_func_time_works="guessing no"],
+           [gl_cv_func_time_works="guessing yes"])
+         ;;
+       *) gl_cv_func_time_works="guessing yes";;
+     esac
+    ])
+  case "$gl_cv_func_time_works" in
+    *no) REPLACE_TIME=1 ;;
+  esac
+])
+
+# Prerequisites of lib/time.c.
+AC_DEFUN([gl_PREREQ_TIME],
+[
+  :
+])
diff --git a/m4/time_h.m4 b/m4/time_h.m4
index b74870c3d0..51d553a2f1 100644
--- a/m4/time_h.m4
+++ b/m4/time_h.m4
@@ -2,7 +2,7 @@
 
 # Copyright (C) 2000-2001, 2003-2007, 2009-2023 Free Software Foundation, Inc.
 
-# serial 21
+# serial 22
 
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -137,6 +137,7 @@ AC_DEFUN([gl_TIME_H_REQUIRE_DEFAULTS],
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_NANOSLEEP])
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRFTIME])
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRPTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIME])
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIMEGM])
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIMESPEC_GET])
     gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIMESPEC_GETRES])
@@ -169,6 +170,7 @@ AC_DEFUN([gl_TIME_H_DEFAULTS],
   REPLACE_MKTIME=GNULIB_PORTCHECK;       AC_SUBST([REPLACE_MKTIME])
   REPLACE_NANOSLEEP=GNULIB_PORTCHECK;    AC_SUBST([REPLACE_NANOSLEEP])
   REPLACE_STRFTIME=GNULIB_PORTCHECK;     AC_SUBST([REPLACE_STRFTIME])
+  REPLACE_TIME=0;                        AC_SUBST([REPLACE_TIME])
   REPLACE_TIMEGM=GNULIB_PORTCHECK;       AC_SUBST([REPLACE_TIMEGM])
   REPLACE_TIMESPEC_GET=GNULIB_PORTCHECK; AC_SUBST([REPLACE_TIMESPEC_GET])
   REPLACE_TZSET=GNULIB_PORTCHECK;        AC_SUBST([REPLACE_TZSET])