build: use more gnulib modules for simpler code

* .gnulib: Update to latest, for sigpipe and sigaction modules.
* bootstrap.conf (gnulib_modules): Add siaction, sigpipe, strerror_r.
* tools/virsh.c (vshSetupSignals) [!SIGPIPE]: Delete, now that
gnulib guarantees it.
(SA_SIGINFO): Define for mingw fallback.
* src/util/virterror.c (virStrerror): Simplify, now that gnulib
guarantees the POSIX interface.
* configure.ac (AC_CHECK_FUNCS_ONCE): Drop redundant check.
(AM_PROG_CC_STDC): Move earlier, to keep autoconf happy.

.gnulib

@@ -1 +1 @@
-Subproject commit 9779055889c2715b593930e39ead552759b5ddc2
+Subproject commit 45d39ca1cae74fcf58ec9911e771bc8baca63f66

bootstrap.conf

@@ -58,12 +58,15 @@ random_r
 sched
 send
 setsockopt
+sigaction
+sigpipe
 snprintf
 socket
 stpcpy
 strchrnul
 strndup
 strerror
+strerror_r-posix
 strptime
 strsep
 strtok_r

configure.ac

@@ -49,11 +49,11 @@ dnl Checks for C compiler.
 AC_PROG_CC
 AC_PROG_INSTALL
 AC_PROG_CPP
+AM_PROG_CC_STDC
 
 gl_EARLY
 gl_INIT
 
-AM_PROG_CC_STDC
 AC_TYPE_UID_T
 
 dnl Make sure we have an ANSI compiler
@@ -93,12 +93,11 @@ fi
 AC_MSG_RESULT([$have_cpuid])
 
 
-dnl Availability of various common functions (non-fatal if missing).
-AC_CHECK_FUNCS_ONCE([cfmakeraw regexec sched_getaffinity getuid getgid initgroups \
- posix_fallocate mmap])
-
-dnl Availability of various not common threadsafe functions
-AC_CHECK_FUNCS_ONCE([strerror_r getmntent_r getgrnam_r getpwuid_r])
+dnl Availability of various common functions (non-fatal if missing),
+dnl and various less common threadsafe functions
+AC_CHECK_FUNCS_ONCE([cfmakeraw regexec sched_getaffinity getuid getgid \
+ initgroups posix_fallocate mmap \
+ getmntent_r getgrnam_r getpwuid_r])
 
 dnl Availability of pthread functions (if missing, win32 threading is
 dnl assumed).  Because of $LIB_PTHREAD, we cannot use AC_CHECK_FUNCS_ONCE.

src/util/virterror.c

@@ -1250,7 +1250,7 @@ void virReportErrorHelper(virConnectPtr conn,
  * @errBuf: the buffer to save the error to
  * @errBufLen: the buffer length
  *
- * Generate an erro string for the given errno
+ * Generate an error string for the given errno
  *
  * Returns a pointer to the error string, possibly indicating that the
  *         error is unknown
@@ -1260,24 +1260,8 @@ const char *virStrerror(int theerrno, char *errBuf, size_t errBufLen)
     int save_errno = errno;
     const char *ret;
 
-#ifdef HAVE_STRERROR_R
-# ifdef __USE_GNU
-    /* Annoying linux specific API contract */
-    ret = strerror_r(theerrno, errBuf, errBufLen);
-# else
     strerror_r(theerrno, errBuf, errBufLen);
     ret = errBuf;
-# endif
-#else
-    /* Mingw lacks strerror_r and its strerror is definitely not
-     * threadsafe, so safest option is to just print the raw errno
-     * value - we can at least reliably & safely look it up in the
-     * header files for debug purposes
-     */
-    int n = snprintf(errBuf, errBufLen, "errno=%d", theerrno);
-    ret = (0 < n && n < errBufLen
-           ? errBuf : _("internal error: buffer too small"));
-#endif
     errno = save_errno;
     return ret;
 }

tools/virsh.c

@@ -497,7 +497,11 @@ out:
  */
 static int disconnected = 0; /* we may have been disconnected */
 
-#ifdef SIGPIPE
+/* Gnulib doesn't guarantee SA_SIGINFO support.  */
+#ifndef SA_SIGINFO
+# define SA_SIGINFO 0
+#endif
+
 /*
  * vshCatchDisconnect:
  *
@@ -506,7 +510,8 @@ static int disconnected = 0; /* we may have been disconnected */
  */
 static void vshCatchDisconnect(int sig, siginfo_t *siginfo,
                                void *context ATTRIBUTE_UNUSED) {
-    if ((sig == SIGPIPE) || (siginfo->si_signo == SIGPIPE))
+    if ((sig == SIGPIPE) ||
+        (SA_SIGINFO && siginfo->si_signo == SIGPIPE))
         disconnected++;
 }
 
@@ -526,10 +531,6 @@ vshSetupSignals(void) {
 
     sigaction(SIGPIPE, &sig_action, NULL);
 }
-#else
-static void
-vshSetupSignals(void) {}
-#endif
 
 /*
  * vshReconnect: