gdb: New maintenance command to disable bfd sharing.

In some rare maintainer cases it is desirable to be able to disable bfd
sharing.  This patch adds new commands maintenance set/show commands for
bfd-sharing, allowing gdb's bfd cache to be turned off.

gdb/ChangeLog:

	* gdb_bfd.c (bfd_sharing): New variable.
	(show_bfd_sharing): New function.
	(gdb_bfd_open): Check bfd_sharing variable.
	(_initialize_gdb_bfd): Add new set/show command.
	* NEWS: Mention new command.

gdb/doc/ChangeLog:

	* gdb.texinfo (Maintenance Commands): Move documentation of "main
	info bfds" to...
	(File Caching): A New section.  Outline bfd caching, and add new
	description for "main set/show bfd-sharing".

1 files changed, 30 insertions, 4 deletions

diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index ee29531..8471775 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -111,6 +111,17 @@ DEFINE_REGISTRY (bfd, GDB_BFD_DATA_ACCESSOR)
 
 static htab_t gdb_bfd_cache;
 
+/* When true gdb will reuse an existing bfd object if the filename,
+   modification time, and file size all match.  */
+
+static int bfd_sharing = 1;
+static void
+show_bfd_sharing  (struct ui_file *file, int from_tty,
+		   struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("BFD sharing is %s.\n"), value);
+}
+
 /* The type of an object being looked up in gdb_bfd_cache.  We use
    htab's capability of storing one kind of object (BFD in this case)
    and using a different sort of object for searching.  */
@@ -394,7 +405,7 @@ gdb_bfd_open (const char *name, const char *target, int fd)
      opening the BFD may fail; and this would violate hashtab
      invariants.  */
   abfd = htab_find_with_hash (gdb_bfd_cache, &search, hash);
-  if (abfd != NULL)
+  if (bfd_sharing && abfd != NULL)
     {
       close (fd);
       gdb_bfd_ref (abfd);
@@ -405,9 +416,12 @@ gdb_bfd_open (const char *name, const char *target, int fd)
   if (abfd == NULL)
     return NULL;
 
-  slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
-  gdb_assert (!*slot);
-  *slot = abfd;
+  if (bfd_sharing)
+    {
+      slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
+      gdb_assert (!*slot);
+      *slot = abfd;
+    }
 
   gdb_bfd_ref (abfd);
   return abfd;
@@ -942,4 +956,16 @@ _initialize_gdb_bfd (void)
   add_cmd ("bfds", class_maintenance, maintenance_info_bfds, _("\
 List the BFDs that are currently open."),
 	   &maintenanceinfolist);
+
+  add_setshow_boolean_cmd ("bfd-sharing", no_class,
+			   &bfd_sharing, _("\
+Set whether gdb will share bfds that appear to be the same file."), _("\
+Show whether gdb will share bfds that appear to be the same file."), _("\
+When enabled gdb will reuse existing bfds rather than reopening the\n\
+same file.  To decide if two files are the same then gdb compares the\n\
+filename, file size, file modification time, and file inode."),
+			   NULL,
+			   &show_bfd_sharing,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
 }