Eliminate make_cleanup_obstack_free, introduce auto_obstack

This commit eliminates make_cleanup_obstack_free, replacing it with a
new auto_obstack type that inherits obstack to add cdtors.

These changes in the parsers may not be obvious:

 -  obstack_init (&name_obstack);
 -  make_cleanup_obstack_free (&name_obstack);
 +  name_obstack.clear ();

Here, the 'name_obstack' variable is a global.  The change means that
the obstack's contents from a previous parse will stay around until
the next parsing starts.  I.e., memory won't be reclaimed until then.
I don't think that's a problem, these objects don't really grow much
at all.

The other option I tried was to add a separate type that is like
auto_obstack but manages an external obstack, just for those cases.  I
like the current approach better as that other approach adds more
boilerplate and yet another type to learn.

gdb/ChangeLog:
2017-06-27  Pedro Alves  <palves@redhat.com>

	* c-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(c_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* c-lang.c (evaluate_subexp_c): Use auto_obstack.
	* d-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(d_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* dwarf2loc.c (fetch_const_value_from_synthetic_pointer): Use
	auto_obstack.
	* dwarf2read.c (create_addrmap_from_index)
	(dwarf2_build_psymtabs_hard)
	(update_enumeration_type_from_children): Likewise.
	* gdb_obstack.h (auto_obstack): New type.
	* go-exp.y (name_obstack): Now an auto_obstack.
	(build_packaged_name): Use auto_obstack::clear.
	(go_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* linux-tdep.c (linux_make_mappings_corefile_notes): Use
	auto_obstack.
	* printcmd.c (printf_wide_c_string, ui_printf): Use auto_obstack.
	* rust-exp.y (work_obstack): Now an auto_obstack.
	(rust_parse, rust_lex_tests): Use auto_obstack::clear instead of
	reinitializing and freeing the obstack.
	* utils.c (do_obstack_free, make_cleanup_obstack_free): Delete.
	(host_char_to_target): Use auto_obstack.
	* utils.h (make_cleanup_obstack_free): Delete declaration.
	* valprint.c (generic_emit_char, generic_printstr): Use
	auto_obstack.

1 files changed, 1 insertions, 6 deletions

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 1afa8d7..2792cbd 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -1506,16 +1506,12 @@ linux_make_mappings_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
 				    char *note_data, int *note_size)
 {
   struct cleanup *cleanup;
-  struct obstack data_obstack, filename_obstack;
   struct linux_make_mappings_data mapping_data;
   struct type *long_type
     = arch_integer_type (gdbarch, gdbarch_long_bit (gdbarch), 0, "long");
   gdb_byte buf[sizeof (ULONGEST)];
 
-  obstack_init (&data_obstack);
-  cleanup = make_cleanup_obstack_free (&data_obstack);
-  obstack_init (&filename_obstack);
-  make_cleanup_obstack_free (&filename_obstack);
+  auto_obstack data_obstack, filename_obstack;
 
   mapping_data.file_count = 0;
   mapping_data.data_obstack = &data_obstack;
@@ -1548,7 +1544,6 @@ linux_make_mappings_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
 				      obstack_object_size (&data_obstack));
     }
 
-  do_cleanups (cleanup);
   return note_data;
 }