Introduce and use gdb::unlinker

This introduces a new class, gdb::unlinker, that unlinks a file in the
destructor.  The user of this class has the option to preserve the
file instead, by calling the "keep" method.

This patch then changes the spots in gdb that use unlink in a cleanup
to use this class instead.  In one spot I went ahead and removed all
the cleanups from the function.

This fixes one latent bug -- do_bfd_delete_cleanup could refer to
freed memory, by decref'ing the BFD before using its filename.

2017-01-10  Tom Tromey  <tom@tromey.com>

	* record-full.c (record_full_save_cleanups): Remove.
	(record_full_save): Use gdb::unlinker.
	* gcore.c (do_bfd_delete_cleanup): Remove.
	(gcore_command): Use gdb::unlinker, unique_xmalloc_ptr.  Remove
	cleanups.
	* dwarf2read.c (unlink_if_set): Remove.
	(write_psymtabs_to_index): Use gdb::unlinker.
	* common/gdb_unlinker.h: New file.

1 files changed, 60 insertions, 0 deletions

diff --git a/gdb/common/gdb_unlinker.h b/gdb/common/gdb_unlinker.h
new file mode 100644
index 0000000..0f3b98a
--- /dev/null
+++ b/gdb/common/gdb_unlinker.h
@@ -0,0 +1,60 @@
+/* Unlinking class
+
+   Copyright (C) 2016 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 GDB_UNLINKER_H
+#define GDB_UNLINKER_H
+
+namespace gdb
+{
+
+/* An object of this class holds a filename and, when the object goes
+   of scope, the file is removed using unlink.
+
+   A user of this class can request that the file be preserved using
+   the "keep" method.  */
+class unlinker
+{
+ public:
+
+  unlinker (const char *filename) ATTRIBUTE_NONNULL (1)
+    : m_filename (filename)
+  {
+    gdb_assert (filename != NULL);
+  }
+
+  ~unlinker ()
+  {
+    if (m_filename != NULL)
+      unlink (m_filename);
+  }
+
+  /* Keep the file, rather than unlink it.  */
+  void keep ()
+  {
+    m_filename = NULL;
+  }
+
+ private:
+
+  const char *m_filename;
+};
+
+}
+
+#endif /* GDB_UNLINKER_H */