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, 22 insertions, 32 deletions

diff --git a/gdb/record-full.c b/gdb/record-full.c
index e4ff6a4e43..fdd613b6e4 100644
--- a/gdb/record-full.c
+++ b/gdb/record-full.c
@@ -35,6 +35,7 @@
 #include "gdb_bfd.h"
 #include "observer.h"
 #include "infrun.h"
+#include "common/gdb_unlinker.h"
 
 #include <signal.h>
 
@@ -2537,17 +2538,6 @@ cmd_record_full_restore (char *args, int from_tty)
   record_full_open (args, from_tty);
 }
 
-static void
-record_full_save_cleanups (void *data)
-{
-  bfd *obfd = (bfd *) data;
-  char *pathname = xstrdup (bfd_get_filename (obfd));
-
-  gdb_bfd_unref (obfd);
-  unlink (pathname);
-  xfree (pathname);
-}
-
 /* Save the execution log to a file.  We use a modified elf corefile
    format, with an extra section for our data.  */
 
@@ -2558,9 +2548,7 @@ record_full_save (struct target_ops *self, const char *recfilename)
   uint32_t magic;
   struct regcache *regcache;
   struct gdbarch *gdbarch;
-  struct cleanup *old_cleanups;
   struct cleanup *set_cleanups;
-  bfd *obfd;
   int save_size = 0;
   asection *osec = NULL;
   int bfd_offset = 0;
@@ -2571,8 +2559,10 @@ record_full_save (struct target_ops *self, const char *recfilename)
 			recfilename);
 
   /* Open the output file.  */
-  obfd = create_gcore_bfd (recfilename).release ();
-  old_cleanups = make_cleanup (record_full_save_cleanups, obfd);
+  gdb_bfd_ref_ptr obfd (create_gcore_bfd (recfilename));
+
+  /* Arrange to remove the output file on failure.  */
+  gdb::unlinker unlink_file (recfilename);
 
   /* Save the current record entry to "cur_record_full_list".  */
   cur_record_full_list = record_full_list;
@@ -2615,20 +2605,20 @@ record_full_save (struct target_ops *self, const char *recfilename)
       }
 
   /* Make the new bfd section.  */
-  osec = bfd_make_section_anyway_with_flags (obfd, "precord",
+  osec = bfd_make_section_anyway_with_flags (obfd.get (), "precord",
                                              SEC_HAS_CONTENTS
                                              | SEC_READONLY);
   if (osec == NULL)
     error (_("Failed to create 'precord' section for corefile %s: %s"),
 	   recfilename,
            bfd_errmsg (bfd_get_error ()));
-  bfd_set_section_size (obfd, osec, save_size);
-  bfd_set_section_vma (obfd, osec, 0);
-  bfd_set_section_alignment (obfd, osec, 0);
-  bfd_section_lma (obfd, osec) = 0;
+  bfd_set_section_size (obfd.get (), osec, save_size);
+  bfd_set_section_vma (obfd.get (), osec, 0);
+  bfd_set_section_alignment (obfd.get (), osec, 0);
+  bfd_section_lma (obfd.get (), osec) = 0;
 
   /* Save corefile state.  */
-  write_gcore_file (obfd);
+  write_gcore_file (obfd.get ());
 
   /* Write out the record log.  */
   /* Write the magic code.  */
@@ -2638,7 +2628,7 @@ record_full_save (struct target_ops *self, const char *recfilename)
 			"  Writing 4-byte magic cookie "
 			"RECORD_FULL_FILE_MAGIC (0x%s)\n",
 		      phex_nz (magic, 4));
-  bfdcore_write (obfd, osec, &magic, sizeof (magic), &bfd_offset);
+  bfdcore_write (obfd.get (), osec, &magic, sizeof (magic), &bfd_offset);
 
   /* Save the entries to recfd and forward execute to the end of
      record list.  */
@@ -2653,7 +2643,7 @@ record_full_save (struct target_ops *self, const char *recfilename)
           uint64_t addr;
 
 	  type = record_full_list->type;
-          bfdcore_write (obfd, osec, &type, sizeof (type), &bfd_offset);
+          bfdcore_write (obfd.get (), osec, &type, sizeof (type), &bfd_offset);
 
           switch (record_full_list->type)
             {
@@ -2668,11 +2658,11 @@ record_full_save (struct target_ops *self, const char *recfilename)
 
               /* Write regnum.  */
               regnum = netorder32 (record_full_list->u.reg.num);
-              bfdcore_write (obfd, osec, &regnum,
+              bfdcore_write (obfd.get (), osec, &regnum,
 			     sizeof (regnum), &bfd_offset);
 
               /* Write regval.  */
-              bfdcore_write (obfd, osec,
+              bfdcore_write (obfd.get (), osec,
 			     record_full_get_loc (record_full_list),
 			     record_full_list->u.reg.len, &bfd_offset);
               break;
@@ -2690,15 +2680,16 @@ record_full_save (struct target_ops *self, const char *recfilename)
 
 	      /* Write memlen.  */
 	      len = netorder32 (record_full_list->u.mem.len);
-	      bfdcore_write (obfd, osec, &len, sizeof (len), &bfd_offset);
+	      bfdcore_write (obfd.get (), osec, &len, sizeof (len),
+			     &bfd_offset);
 
 	      /* Write memaddr.  */
 	      addr = netorder64 (record_full_list->u.mem.addr);
-	      bfdcore_write (obfd, osec, &addr, 
+	      bfdcore_write (obfd.get (), osec, &addr, 
 			     sizeof (addr), &bfd_offset);
 
 	      /* Write memval.  */
-	      bfdcore_write (obfd, osec,
+	      bfdcore_write (obfd.get (), osec,
 			     record_full_get_loc (record_full_list),
 			     record_full_list->u.mem.len, &bfd_offset);
               break;
@@ -2712,12 +2703,12 @@ record_full_save (struct target_ops *self, const char *recfilename)
 				      (unsigned long) sizeof (count));
 		/* Write signal value.  */
 		signal = netorder32 (record_full_list->u.end.sigval);
-		bfdcore_write (obfd, osec, &signal,
+		bfdcore_write (obfd.get (), osec, &signal,
 			       sizeof (signal), &bfd_offset);
 
 		/* Write insn count.  */
 		count = netorder32 (record_full_list->u.end.insn_num);
-		bfdcore_write (obfd, osec, &count,
+		bfdcore_write (obfd.get (), osec, &count,
 			       sizeof (count), &bfd_offset);
                 break;
             }
@@ -2746,8 +2737,7 @@ record_full_save (struct target_ops *self, const char *recfilename)
     }
 
   do_cleanups (set_cleanups);
-  gdb_bfd_unref (obfd);
-  discard_cleanups (old_cleanups);
+  unlink_file.keep ();
 
   /* Succeeded.  */
   printf_filtered (_("Saved core file %s with execution log.\n"),