Update from Gnulib.

This incorporates:
2019-03-23 Support cross-compilation to musl libc
2019-03-23 noreturn: In C++ mode with clang, use _Noreturn as fallback
2019-03-22 _Noreturn: beware of C's _Noreturn in C++ pre C++11
2019-03-19 Help making signal handlers more reliable
2019-03-18 _Noreturn: clang and MSVC do support [[noreturn]] in C++11
2019-03-17 _Noreturn: GCC 4.7 does not support [[noreturn]] in C++11
2019-03-14 all: Update URLs to msdn.microsoft.com
* doc/misc/texinfo.tex, lib/_Noreturn.h, lib/gettimeofday.c:
* lib/mktime.c, lib/regcomp.c, lib/regexec.c, lib/stat-time.h:
* lib/utimens.c, m4/fdopendir.m4, m4/getgroups.m4:
* m4/gettimeofday.m4, m4/gnulib-common.m4, m4/putenv.m4, m4/utimes.m4:
Update from gnulib.

6 files changed, 58 insertions, 16 deletions

diff --git a/m4/fdopendir.m4 b/m4/fdopendir.m4
index 04905519d0b..b2b3b037316 100644
--- a/m4/fdopendir.m4
+++ b/m4/fdopendir.m4
@@ -1,4 +1,4 @@
-# serial 10
+# serial 11
 # See if we need to provide fdopendir.
 
 dnl Copyright (C) 2009-2019 Free Software Foundation, Inc.
@@ -45,10 +45,12 @@ DIR *fdopendir (int);
          [gl_cv_func_fdopendir_works=yes],
          [gl_cv_func_fdopendir_works=no],
          [case "$host_os" in
-                    # Guess yes on glibc systems.
-            *-gnu*) gl_cv_func_fdopendir_works="guessing yes" ;;
-                    # If we don't know, assume the worst.
-            *)      gl_cv_func_fdopendir_works="guessing no" ;;
+                     # Guess yes on glibc systems.
+            *-gnu*)  gl_cv_func_fdopendir_works="guessing yes" ;;
+                     # Guess yes on musl systems.
+            *-musl*) gl_cv_func_fdopendir_works="guessing yes" ;;
+                     # If we don't know, assume the worst.
+            *)       gl_cv_func_fdopendir_works="guessing no" ;;
           esac
          ])])
     case "$gl_cv_func_fdopendir_works" in
diff --git a/m4/getgroups.m4 b/m4/getgroups.m4
index 2ce986ea79b..c93447bb11c 100644
--- a/m4/getgroups.m4
+++ b/m4/getgroups.m4
@@ -1,4 +1,4 @@
-# serial 21
+# serial 22
 
 dnl From Jim Meyering.
 dnl A wrapper around AC_FUNC_GETGROUPS.
@@ -42,6 +42,8 @@ AC_DEFUN([AC_FUNC_GETGROUPS],
          [case "$host_os" in # ((
                            # Guess yes on glibc systems.
             *-gnu* | gnu*) ac_cv_func_getgroups_works="guessing yes" ;;
+                           # Guess yes on musl systems.
+            *-musl*)       ac_cv_func_getgroups_works="guessing yes" ;;
                            # If we don't know, assume the worst.
             *)             ac_cv_func_getgroups_works="guessing no" ;;
           esac
@@ -95,6 +97,8 @@ AC_DEFUN([gl_FUNC_GETGROUPS],
           [case "$host_os" in
                             # Guess yes on glibc systems.
              *-gnu* | gnu*) gl_cv_func_getgroups_works="guessing yes" ;;
+                            # Guess yes on musl systems.
+             *-musl*)       gl_cv_func_getgroups_works="guessing yes" ;;
                             # If we don't know, assume the worst.
              *)             gl_cv_func_getgroups_works="guessing no" ;;
            esac
diff --git a/m4/gettimeofday.m4 b/m4/gettimeofday.m4
index d29b4bff2ff..5e2ef6f47e2 100644
--- a/m4/gettimeofday.m4
+++ b/m4/gettimeofday.m4
@@ -1,4 +1,4 @@
-# serial 25
+# serial 26
 
 # Copyright (C) 2001-2003, 2005, 2007, 2009-2019 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
@@ -105,6 +105,8 @@ AC_DEFUN([gl_FUNC_GETTIMEOFDAY_CLOBBER],
       case "$host_os" in
                        # Guess all is fine on glibc systems.
         *-gnu* | gnu*) gl_cv_func_gettimeofday_clobber="guessing no" ;;
+                       # Guess all is fine on musl systems.
+        *-musl*)       gl_cv_func_gettimeofday_clobber="guessing no" ;;
                        # Guess no on native Windows.
         mingw*)        gl_cv_func_gettimeofday_clobber="guessing no" ;;
                        # If we don't know, assume the worst.
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index 7c0e3e8fa4a..57b94ed5325 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 41
+# gnulib-common.m4 serial 44
 dnl Copyright (C) 2007-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -17,10 +17,13 @@ AC_DEFUN([gl_COMMON_BODY], [
   AH_VERBATIM([_Noreturn],
 [/* The _Noreturn keyword of C11.  */
 #ifndef _Noreturn
-# if 201103 <= (defined __cplusplus ? __cplusplus : 0)
+# if (defined __cplusplus \
+      && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
+          || (defined _MSC_VER && 1900 <= _MSC_VER)))
 #  define _Noreturn [[noreturn]]
-# elif (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \
-        || 4 < __GNUC__ + (7 <= __GNUC_MINOR__))
+# elif ((!defined __cplusplus || defined __clang__) \
+        && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0)  \
+            || 4 < __GNUC__ + (7 <= __GNUC_MINOR__)))
    /* _Noreturn works as-is.  */
 # elif 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || 0x5110 <= __SUNPRO_C
 #  define _Noreturn __attribute__ ((__noreturn__))
@@ -85,6 +88,33 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_MALLOC /* empty */
 #endif
 ])
+  AH_VERBATIM([async_safe],
+[/* The _GL_ASYNC_SAFE marker should be attached to functions that are
+   signal handlers (for signals other than SIGABRT, SIGPIPE) or can be
+   invoked from such signal handlers.  Such functions have some restrictions:
+     * All functions that it calls should be marked _GL_ASYNC_SAFE as well,
+       or should be listed as async-signal-safe in POSIX
+       <http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04>
+       section 2.4.3.  Note that malloc(), sprintf(), and fwrite(), in
+       particular, are NOT async-signal-safe.
+     * All memory locations (variables and struct fields) that these functions
+       access must be marked 'volatile'.  This holds for both read and write
+       accesses.  Otherwise the compiler might optimize away stores to and
+       reads from such locations that occur in the program, depending on its
+       data flow analysis.  For example, when the program contains a loop
+       that is intended to inspect a variable set from within a signal handler
+           while (!signal_occurred)
+             ;
+       the compiler is allowed to transform this into an endless loop if the
+       variable 'signal_occurred' is not declared 'volatile'.
+   Additionally, recall that:
+     * A signal handler should not modify errno (except if it is a handler
+       for a fatal signal and ends by raising the same signal again, thus
+       provoking the termination of the process).  If it invokes a function
+       that may clobber errno, it needs to save and restore the value of
+       errno.  */
+#define _GL_ASYNC_SAFE
+])
   dnl Preparation for running test programs:
   dnl Tell glibc to write diagnostics from -D_FORTIFY_SOURCE=2 to stderr, not
   dnl to /dev/tty, so they can be redirected to log files.  Such diagnostics
diff --git a/m4/putenv.m4 b/m4/putenv.m4
index f8960f66be5..342ba2636ab 100644
--- a/m4/putenv.m4
+++ b/m4/putenv.m4
@@ -1,4 +1,4 @@
-# putenv.m4 serial 22
+# putenv.m4 serial 23
 dnl Copyright (C) 2002-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -36,6 +36,8 @@ AC_DEFUN([gl_FUNC_PUTENV],
              [case "$host_os" in
                                # Guess yes on glibc systems.
                 *-gnu* | gnu*) gl_cv_func_svid_putenv="guessing yes" ;;
+                               # Guess yes on musl systems.
+                *-musl*)       gl_cv_func_svid_putenv="guessing yes" ;;
                                # Guess no on native Windows.
                 mingw*)        gl_cv_func_svid_putenv="guessing no" ;;
                                # If we don't know, assume the worst.
diff --git a/m4/utimes.m4 b/m4/utimes.m4
index 7209b6dd599..5806d8fbbb6 100644
--- a/m4/utimes.m4
+++ b/m4/utimes.m4
@@ -1,5 +1,5 @@
 # Detect some bugs in glibc's implementation of utimes.
-# serial 5
+# serial 6
 
 dnl Copyright (C) 2003-2005, 2009-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
@@ -143,9 +143,11 @@ main ()
        [gl_cv_func_working_utimes=yes],
        [gl_cv_func_working_utimes=no],
        [case "$host_os" in
-                  # Guess no on native Windows.
-          mingw*) gl_cv_func_working_utimes="guessing no" ;;
-          *)      gl_cv_func_working_utimes="guessing no" ;;
+                   # Guess yes on musl systems.
+          *-musl*) gl_cv_func_working_utimes="guessing yes" ;;
+                   # Guess no on native Windows.
+          mingw*)  gl_cv_func_working_utimes="guessing no" ;;
+          *)       gl_cv_func_working_utimes="guessing no" ;;
         esac
        ])
     ])