common: add scoped_fd

Add a simple helper to automatically close a file descriptor.

gdb/
	* common/scoped_fd.h: New.
	* unittests/scoped_fd-selftest.c: New.
	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
	unittests/scoped_fd-selftest.c.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2018-02-09  Markus Metzger  <markus.t.metzger@intel.com>
+
+	* common/scoped_fd.h: New.
+	* unittests/scoped_fd-selftest.c: New.
+	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
+	unittests/scoped_fd-selftest.c.
+
 2018-02-09  Tom Tromey  <tom@tromey.com>
 
 	* auto-load.c (auto_load_section_scripts): Use

gdb/Makefile.in

@@ -424,6 +424,7 @@ SUBDIR_UNITTESTS_SRCS = \
 	unittests/optional-selftests.c \
 	unittests/ptid-selftests.c \
 	unittests/rsp-low-selftests.c \
+	unittests/scoped_fd-selftests.c \
 	unittests/scoped_restore-selftests.c \
 	unittests/xml-utils-selftests.c
 

gdb/common/scoped_fd.h

@@ -0,0 +1,60 @@
+/* scoped_fd, automatically close a file descriptor
+
+   Copyright (C) 2018 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/>.  */
+
+#ifndef SCOPED_FD_H
+#define SCOPED_FD_H
+
+#include "config.h"
+
+#ifdef HAVE_UNISTD_H
+
+#include <unistd.h>
+
+/* A smart-pointer-like class to automatically close a file descriptor.  */
+
+class scoped_fd
+{
+public:
+  explicit scoped_fd (int fd = -1) noexcept : m_fd (fd) {}
+  ~scoped_fd ()
+  {
+    if (m_fd >= 0)
+      close (m_fd);
+  }
+
+  DISABLE_COPY_AND_ASSIGN (scoped_fd);
+
+  int release () noexcept
+  {
+    int fd = m_fd;
+    m_fd = -1;
+    return fd;
+  }
+
+  int get () const noexcept
+  {
+    return m_fd;
+  }
+
+private:
+  int m_fd;
+};
+
+#endif /* HAVE_UNISTD_H */
+#endif /* SCOPED_FD_H */

gdb/unittests/scoped_fd-selftests.c

@@ -0,0 +1,90 @@
+/* Self tests for scoped_fd for GDB, the GNU debugger.
+
+   Copyright (C) 2018 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 "common/scoped_fd.h"
+#include "config.h"
+
+#ifdef HAVE_UNISTD_H
+
+#include "selftest.h"
+
+namespace selftests {
+namespace scoped_fd {
+
+/* Test that the file descriptor is closed.  */
+static void
+test_destroy ()
+{
+  char filename[] = "scoped_fd-selftest-XXXXXX";
+  int fd = mkstemp (filename);
+  SELF_CHECK (fd >= 0);
+
+  unlink (filename);
+  errno = 0;
+  {
+    ::scoped_fd sfd (fd);
+
+    SELF_CHECK (sfd.get () == fd);
+  }
+
+  SELF_CHECK (close (fd) == -1 && errno == EBADF);
+}
+
+/* Test that the file descriptor can be released.  */
+static void
+test_release ()
+{
+  char filename[] = "scoped_fd-selftest-XXXXXX";
+  int fd = mkstemp (filename);
+  SELF_CHECK (fd >= 0);
+
+  unlink (filename);
+  errno = 0;
+  {
+    ::scoped_fd sfd (fd);
+
+    SELF_CHECK (sfd.release () == fd);
+  }
+
+  SELF_CHECK (close (fd) == 0 || errno != EBADF);
+}
+
+/* Run selftests.  */
+static void
+run_tests ()
+{
+  test_destroy ();
+  test_release ();
+}
+
+} /* namespace scoped_fd */
+} /* namespace selftests */
+
+#endif /* HAVE_UNISTD_H */
+
+void
+_initialize_scoped_fd_selftests ()
+{
+#ifdef HAVE_UNISTD_H
+  selftests::register_test ("scoped_fd",
+			    selftests::scoped_fd::run_tests);
+#endif
+}