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, 5 insertions, 4 deletions

diff --git a/gdb/go-exp.y b/gdb/go-exp.y
index 057e227..f2f3596 100644
--- a/gdb/go-exp.y
+++ b/gdb/go-exp.y
@@ -1297,7 +1297,7 @@ static int popping;
 
 /* Temporary storage for yylex; this holds symbol names as they are
    built up.  */
-static struct obstack name_obstack;
+static auto_obstack name_obstack;
 
 /* Build "package.name" in name_obstack.
    For convenience of the caller, the name is NUL-terminated,
@@ -1309,7 +1309,7 @@ build_packaged_name (const char *package, int package_len,
 {
   struct stoken result;
 
-  obstack_free (&name_obstack, obstack_base (&name_obstack));
+  name_obstack.clear ();
   obstack_grow (&name_obstack, package, package_len);
   obstack_grow_str (&name_obstack, ".");
   obstack_grow (&name_obstack, name, name_len);
@@ -1567,6 +1567,8 @@ go_parse (struct parser_state *par_state)
   gdb_assert (par_state != NULL);
   pstate = par_state;
 
+  /* Note that parsing (within yyparse) freely installs cleanups
+     assuming they'll be run here (below).  */
   back_to = make_cleanup (null_cleanup, NULL);
 
   scoped_restore restore_yydebug = make_scoped_restore (&yydebug,
@@ -1579,8 +1581,7 @@ go_parse (struct parser_state *par_state)
 
   VEC_free (token_and_value, token_fifo);
   popping = 0;
-  obstack_init (&name_obstack);
-  make_cleanup_obstack_free (&name_obstack);
+  name_obstack.clear ();
 
   result = yyparse ();
   do_cleanups (back_to);