Add a unit test for scoped_ignore_sigpipe

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* Makefile.in (SELFTESTS_SRCS): Add
	unittests/scoped_ignore_signal-selftests.c.
	* unittests/scoped_ignore_signal-selftests.c: New.

Change-Id: Idce24aa9432a3f1eb7065bc9aa030b1d0d7dcad5

1 files changed, 126 insertions, 0 deletions

diff --git a/gdb/unittests/scoped_ignore_signal-selftests.c b/gdb/unittests/scoped_ignore_signal-selftests.c
new file mode 100644
index 00000000000..29826e325dc
--- /dev/null
+++ b/gdb/unittests/scoped_ignore_signal-selftests.c
@@ -0,0 +1,126 @@
+/* Self tests for scoped_ignored_signal for GDB, the GNU debugger.
+
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "gdbsupport/scoped_ignore_signal.h"
+#include "gdbsupport/selftest.h"
+#include "gdbsupport/scope-exit.h"
+#include <unistd.h>
+#include <signal.h>
+
+namespace selftests {
+namespace scoped_ignore_sig {
+
+#ifdef SIGPIPE
+
+/* True if the SIGPIPE handler ran.  */
+static volatile sig_atomic_t got_sigpipe = 0;
+
+/* SIGPIPE handler for testing.  */
+
+static void
+handle_sigpipe (int)
+{
+  got_sigpipe = 1;
+}
+
+/* Test scoped_ignore_sigpipe.  */
+
+static void
+test_sigpipe ()
+{
+  auto *osig = signal (SIGPIPE, handle_sigpipe);
+  SCOPE_EXIT { signal (SIGPIPE, osig); };
+
+#ifdef HAVE_SIGPROCMASK
+  /* Make sure SIGPIPE isn't blocked.  */
+  sigset_t set, old_state;
+  sigemptyset (&set);
+  sigaddset (&set, SIGPIPE);
+  sigprocmask (SIG_UNBLOCK, &set, &old_state);
+  SCOPE_EXIT { sigprocmask (SIG_SETMASK, &old_state, nullptr); };
+#endif
+
+  /* Create pipe, and close read end so that writes to the pipe fail
+     with EPIPE.  */
+
+  int fd[2];
+  char c = 0xff;
+  int r;
+
+  r = pipe (fd);
+  SELF_CHECK (r == 0);
+
+  close (fd[0]);
+  SCOPE_EXIT { close (fd[1]); };
+
+  /* Check that writing to the pipe results in EPIPE.  EXPECT_SIG
+     indicates whether a SIGPIPE signal is expected.  */
+  auto check_pipe_write = [&] (bool expect_sig)
+  {
+    got_sigpipe = 0;
+    errno = 0;
+
+    r = write (fd[1], &c, 1);
+    SELF_CHECK (r == -1 && errno == EPIPE
+		&& got_sigpipe == expect_sig);
+  };
+
+  /* Check that without a scoped_ignore_sigpipe in scope we indeed get
+     a SIGPIPE signal.  */
+  check_pipe_write (true);
+
+  /* Now check that with a scoped_ignore_sigpipe in scope, SIGPIPE is
+     ignored/blocked.  */
+  {
+    scoped_ignore_sigpipe ignore1;
+
+    check_pipe_write (false);
+
+    /* Check that scoped_ignore_sigpipe nests correctly.  */
+    {
+      scoped_ignore_sigpipe ignore2;
+
+      check_pipe_write (false);
+    }
+
+    /* If nesting works correctly, this write results in no
+       SIGPIPE.  */
+    check_pipe_write (false);
+  }
+
+  /* No scoped_ignore_sigpipe is in scope anymore, so this should
+     result in a SIGPIPE signal.  */
+  check_pipe_write (true);
+}
+
+#endif /* SIGPIPE */
+
+} /* namespace scoped_ignore_sig */
+} /* namespace selftests */
+
+void _initialize_scoped_ignore_signal_selftests ();
+void
+_initialize_scoped_ignore_signal_selftests ()
+{
+#ifdef SIGPIPE
+  selftests::register_test ("scoped_ignore_sigpipe",
+			    selftests::scoped_ignore_sig::test_sigpipe);
+#endif
+}