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, 12 insertions, 26 deletions

diff --git a/gdb/gcore.c b/gdb/gcore.c
index 1d8a63f04cf..c32d2fff27d 100644
--- a/gdb/gcore.c
+++ b/gdb/gcore.c
@@ -35,6 +35,7 @@
 #include "gdb_bfd.h"
 #include "readline/tilde.h"
 #include <algorithm>
+#include "common/gdb_unlinker.h"
 
 /* The largest amount of memory to read from the target at once.  We
    must throttle it to limit the amount of memory used by GDB during
@@ -135,59 +136,44 @@ write_gcore_file (bfd *obfd)
     throw_exception (except);
 }
 
-static void
-do_bfd_delete_cleanup (void *arg)
-{
-  bfd *obfd = (bfd *) arg;
-  const char *filename = obfd->filename;
-
-  gdb_bfd_unref ((bfd *) arg);
-  unlink (filename);
-}
-
 /* gcore_command -- implements the 'gcore' command.
    Generate a core file from the inferior process.  */
 
 static void
 gcore_command (char *args, int from_tty)
 {
-  struct cleanup *filename_chain;
-  struct cleanup *bfd_chain;
-  char *corefilename;
-  bfd *obfd;
+  gdb::unique_xmalloc_ptr<char> corefilename;
 
   /* No use generating a corefile without a target process.  */
   if (!target_has_execution)
     noprocess ();
 
   if (args && *args)
-    corefilename = tilde_expand (args);
+    corefilename.reset (tilde_expand (args));
   else
     {
       /* Default corefile name is "core.PID".  */
-      corefilename = xstrprintf ("core.%d", ptid_get_pid (inferior_ptid));
+      corefilename.reset (xstrprintf ("core.%d", ptid_get_pid (inferior_ptid)));
     }
-  filename_chain = make_cleanup (xfree, corefilename);
 
   if (info_verbose)
     fprintf_filtered (gdb_stdout,
-		      "Opening corefile '%s' for output.\n", corefilename);
+		      "Opening corefile '%s' for output.\n",
+		      corefilename.get ());
 
   /* Open the output file.  */
-  obfd = create_gcore_bfd (corefilename).release ();
+  gdb_bfd_ref_ptr obfd (create_gcore_bfd (corefilename.get ()));
 
-  /* Need a cleanup that will close and delete the file.  */
-  bfd_chain = make_cleanup (do_bfd_delete_cleanup, obfd);
+  /* Arrange to unlink the file on failure.  */
+  gdb::unlinker unlink_file (corefilename.get ());
 
   /* Call worker function.  */
-  write_gcore_file (obfd);
+  write_gcore_file (obfd.get ());
 
   /* Succeeded.  */
-  discard_cleanups (bfd_chain);
-  gdb_bfd_unref (obfd);
+  unlink_file.keep ();
 
-  fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
-  do_cleanups (filename_chain);
+  fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename.get ());
 }
 
 static unsigned long