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, 4 insertions, 13 deletions

diff --git a/gdb/valprint.c b/gdb/valprint.c
index c10dade674..166788279a 100644
--- a/gdb/valprint.c
+++ b/gdb/valprint.c
@@ -2484,8 +2484,6 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
 {
   enum bfd_endian byte_order
     = gdbarch_byte_order (get_type_arch (type));
-  struct obstack wchar_buf, output;
-  struct cleanup *cleanups;
   gdb_byte *buf;
   int need_escape = 0;
 
@@ -2495,8 +2493,7 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
   wchar_iterator iter (buf, TYPE_LENGTH (type), encoding, TYPE_LENGTH (type));
 
   /* This holds the printable form of the wchar_t data.  */
-  obstack_init (&wchar_buf);
-  cleanups = make_cleanup_obstack_free (&wchar_buf);
+  auto_obstack wchar_buf;
 
   while (1)
     {
@@ -2543,8 +2540,7 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
     }
 
   /* The output in the host encoding.  */
-  obstack_init (&output);
-  make_cleanup_obstack_free (&output);
+  auto_obstack output;
 
   convert_between_encodings (INTERMEDIATE_ENCODING, host_charset (),
 			     (gdb_byte *) obstack_base (&wchar_buf),
@@ -2553,8 +2549,6 @@ generic_emit_char (int c, struct type *type, struct ui_file *stream,
   obstack_1grow (&output, '\0');
 
   fputs_filtered ((const char *) obstack_base (&output), stream);
-
-  do_cleanups (cleanups);
 }
 
 /* Return the repeat count of the next character/byte in ITER,
@@ -2813,7 +2807,6 @@ generic_printstr (struct ui_file *stream, struct type *type,
   enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));
   unsigned int i;
   int width = TYPE_LENGTH (type);
-  struct obstack wchar_buf, output;
   struct cleanup *cleanup;
   int finished = 0;
   struct converted_character *last;
@@ -2885,8 +2878,7 @@ generic_printstr (struct ui_file *stream, struct type *type,
 
   /* WCHAR_BUF is the obstack we use to represent the string in
      wchar_t form.  */
-  obstack_init (&wchar_buf);
-  make_cleanup_obstack_free (&wchar_buf);
+  auto_obstack wchar_buf;
 
   /* Print the output string to the obstack.  */
   print_converted_chars_to_obstack (&wchar_buf, converted_chars, quote_char,
@@ -2896,8 +2888,7 @@ generic_printstr (struct ui_file *stream, struct type *type,
     obstack_grow_wstr (&wchar_buf, LCST ("..."));
 
   /* OUTPUT is where we collect `char's for printing.  */
-  obstack_init (&output);
-  make_cleanup_obstack_free (&output);
+  auto_obstack output;
 
   convert_between_encodings (INTERMEDIATE_ENCODING, host_charset (),
 			     (gdb_byte *) obstack_base (&wchar_buf),