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, 9 insertions, 6 deletions

diff --git a/gdb/rust-exp.y b/gdb/rust-exp.y
index 64b7c55..c7361bc 100644
--- a/gdb/rust-exp.y
+++ b/gdb/rust-exp.y
@@ -185,7 +185,7 @@ static int unit_testing;
 
 /* Obstack for data temporarily allocated during parsing.  */
 
-static struct obstack work_obstack;
+static auto_obstack work_obstack;
 
 /* Result of parsing.  Points into work_obstack.  */
 
@@ -2446,13 +2446,17 @@ int
 rust_parse (struct parser_state *state)
 {
   int result;
-  struct cleanup *cleanup;
 
-  obstack_init (&work_obstack);
-  cleanup = make_cleanup_obstack_free (&work_obstack);
+  work_obstack.clear ();
+
   rust_ast = NULL;
 
   pstate = state;
+
+  /* Note that parsing (within rustyyparse) freely installs cleanups
+     assuming they're run here (below).  */
+  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+
   result = rustyyparse ();
 
   if (!result || (parse_completion && rust_ast != NULL))
@@ -2631,7 +2635,7 @@ rust_lex_tests (void)
 {
   int i;
 
-  obstack_init (&work_obstack);
+  work_obstack.clear ();
   unit_testing = 1;
 
   rust_lex_test_one ("", 0);
@@ -2722,7 +2726,6 @@ rust_lex_tests (void)
   rust_lex_test_completion ();
   rust_lex_test_push_back ();
 
-  obstack_free (&work_obstack, NULL);
   unit_testing = 0;
 }