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, 2 insertions, 10 deletions

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index f392e6d..a8cc052 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -2255,8 +2255,6 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
 					 "wchar_t", NULL, 0);
   int wcwidth = TYPE_LENGTH (wctype);
   gdb_byte *buf = (gdb_byte *) alloca (wcwidth);
-  struct obstack output;
-  struct cleanup *inner_cleanup;
 
   tem = value_as_address (value);
 
@@ -2275,8 +2273,7 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
     read_memory (tem, str, j);
   memset (&str[j], 0, wcwidth);
 
-  obstack_init (&output);
-  inner_cleanup = make_cleanup_obstack_free (&output);
+  auto_obstack output;
 
   convert_between_encodings (target_wide_charset (gdbarch),
 			     host_charset (),
@@ -2285,7 +2282,6 @@ printf_wide_c_string (struct ui_file *stream, const char *format,
   obstack_grow_str0 (&output, "");
 
   fprintf_filtered (stream, format, obstack_base (&output));
-  do_cleanups (inner_cleanup);
 }
 
 /* Subroutine of ui_printf to simplify it.
@@ -2531,8 +2527,6 @@ ui_printf (const char *arg, struct ui_file *stream)
 	      struct type *wctype = lookup_typename (current_language, gdbarch,
 						     "wchar_t", NULL, 0);
 	      struct type *valtype;
-	      struct obstack output;
-	      struct cleanup *inner_cleanup;
 	      const gdb_byte *bytes;
 
 	      valtype = value_type (val_args[i]);
@@ -2542,8 +2536,7 @@ ui_printf (const char *arg, struct ui_file *stream)
 
 	      bytes = value_contents (val_args[i]);
 
-	      obstack_init (&output);
-	      inner_cleanup = make_cleanup_obstack_free (&output);
+	      auto_obstack output;
 
 	      convert_between_encodings (target_wide_charset (gdbarch),
 					 host_charset (),
@@ -2554,7 +2547,6 @@ ui_printf (const char *arg, struct ui_file *stream)
 
 	      fprintf_filtered (stream, current_substring,
                                 obstack_base (&output));
-	      do_cleanups (inner_cleanup);
 	    }
 	    break;
 	  case double_arg: